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Yellowstone: Cloning the Apple II Liron

FPGA-based disk control for Apple II is finally working! Six months ago, I began designing a universal disk controller card for the Apple II family. Apple made a bewildering number of different disk controller cards in the 1970s and 80s, and my hope was to replace the IWM chip (Integrated Wozniak Machine) and other assorted ICs typically found on the cards, and substitute a modern FPGA. With a little luck, that would make it possible to clone any vintage disk controller card – some of which are now rare and expensive. It would also enable a single card to function as many different disk controllers, simply by modifying the FPGA configuration. With the successful cloning of a Liron disk controller, the first major step towards those goals has been made.

Six months passed from the initial design until now, but it wasn’t exactly six months of continuous work. After a short spurt of activity last summer, the project sat collecting dust on my desk until I recently picked it up again. Sometimes it’s hard to find motivation!

Hello Liron

The “Liron” disk controller was introduced by Apple in 1985. More formally known as the Apple II UniDisk 3.5 Controller, it’s designed to work with a new generation of “smart” disk drives more sophisticated than the venerable Disk II 5.25 inch floppy drive. The smart disk port on the Liron is appropriately named the Smartport, and it can communicate with block-based storage devices such as the Unidisk 3.5 (an early 800K drive) and Smartport-based Apple II hard drives.

Why care about the Liron? The Apple IIc and Apple IIgs have integrated disk ports with built-in Smartport functionality, but for the earlier Apple II+ and IIe, the Liron is the only way to get a Smartport. For owners of the BMOW Floppy Emu disk emulator, the Liron card makes it possible to use the Floppy Emu as an external hard drive for the II+ and IIe. Unfortunately finding a Liron is difficult, and although they occasionally turn up on eBay, they’re quite expensive. That made cloning the Liron a logical first goal.

John Holmes was kind enough to lend me his Liron card for examination. Later Roger Shimada made the generous gift of a Liron and a Unidisk 3.5. I’m indebted to both of these kind gentlemen for their help.

The Liron contains an IWM chip, a 4K ROM, and a handful of 7400-series glue logic chips. It took a few hours to trace all the connections on the card and create a schematic. Except for the IWM, the exact functions of the other chips are all well known and relatively easy to implement in a hardware description language for the FPGA. Fortunately there’s a spec sheet for the IWM too, written by Woz himself, available if you search through dusty corners of the Internet. Based on that information, I was able to create an HDL model of the IWM for synthesis in the FPGA. It was a fairly big project, but I’d already done part of it back in 2011 for my Plus Too Mac replica.

Yellowstone Prototype

The first Yellowstone prototype was sketched out during a single hectic week. I’d never made an Apple II card before, but it’s just a standard thickness PCB with a specific shape and pattern of edge connectors. The core of the Yellowstone board is a Lattice MachXO2 FPGA, specifically the LCMXO2-1200HC. This 100-pin chip has 1280 LUTs for implementing logic, and 8 KB of embedded block RAM to serve as the boot ROM or for other functions. It also has some nice features like a built-in PLL oscillator and integrated programmable pull-up and pull-down resistors. Unlike some FPGAs, the MachXO2 family has built-in flash memory to store the FPGA configuration, so it doesnโ€™t need to be reloaded from an external source at power-up. The FPGA can be programmed through a JTAG header on the card.

Because the FPGA’s maximum supported I/O voltage is 3.3V, but the Apple II has a 5V bus, some level conversion is needed. I used four 74LVC245 chips as bus drivers. These chips operate at 3.3V but are fully 5V tolerant, and the Apple II happily accepts their 3.3V output as a valid logic “high”. One of the chips operates bidirectionally on the data bus, and the others handle the unidirectional address bus and control signals.

The prototype card also has a 2 MB serial EEPROM. I’m not exactly sure how this will be used, but I’m hoping to find a way to load disk images from the EEPROM as well as load disks from a real drive. 2 MB is enough to store 14 disk images of 5.25 inch disks, or a single larger disk image. It’s not central to the design, but if it works it would be exciting.

To make the physical connection to an external disk drive, I attached a short cable to another custom PCB with a DB19-F connector. The female version of the DB19 isn’t quite as difficult to find as the male, but it’s not exactly common. If Yellowstone eventually becomes a product and sells in any appreciable volume, obtaining sufficient supplies of the DB19-F will likely be a problem.

Putting it All Together

After months of procrastination, and a long digression into what proved to be a faulty JTAG programmer, I was finally ready to put Yellowstone to the test. After a few quick fixes, it worked right away! I was very surprised, considering that the complex IWM model for the FPGA was developed without any iterative testing or validation. I got lucky this time.

Here’s Yellowstone, booting an Apple IIe from a 6 MB hard disk image using a Floppy Emu Model B in Smartport mode:

And here’s Yellowstone again, booting an 800K ProDOS master disk from an Apple Unidisk 3.5 drive:

What’s Next?

I’ve made it this far – phew! Next, there are lots of little things to fix on the card. Some parts are labeled incorrectly, it’s slightly too wide, some extra resistors and buffers are probably needed for safety, etc. Addressing all those items will keep me busy for a while.

Second, I’d like to investigate cloning other types of Apple II disk controllers. The Disk II controller card should be fairly easy to clone – or the Disk 5.25 controller, which is essentially the same card with a different physical connector. I’m about 90% sure I can make that work. I would love to clone the Apple II 3.5 Disk Controller too (aka the Superdrive controller), but that would be a much larger effort and I’m not certain it’s possible. I believe the real Superdrive controller contains an independent 6502 CPU and is quite complex.

In theory the Yellowstone card could also implement other non-disk functions, although it might require a different physical connector to make use of them. A serial card maybe? Some kind of networking? A coprocessor?

The elephant in the room is the question of Yellowstone’s ultimate goal. Is it a hobby project, or a product? If a product, how much demand really exists for something like this? How would the demand change, depending on what kinds of other disk controllers I’m ultimately able to clone? And how would Yellowstone buyers update the FPGA with new firmware for new clones and bug fixes? I probably can’t assume that every customer owns a JTAG programmer and has the tools and skills to use it. But I’m reluctant to add a USB interface or microcontroller that’s used solely for JTAG/firmware updates and is dead weight otherwise. I’m still waiting for a great solution to hit me.

I’m happy the Apple II bus interface is so easy to understand and implement. Thanks to Woz for that. With just a ROM and a bit of glue logic (or their equivalents in FPGA), you can do all sorts of creative things. With today’s computers being such closed systems, I’m glad we still have antiques like the Apple II to provide an outlet for my electronics tinkering.

Read 62 comments and join the conversation 

62 Comments so far

  1. Tim Buchheim - January 31st, 2018 5:04 pm

    The 8-bit Apple II community would be pretty happy with just a LIRON clone.

    A LIRON clone is not quite as useful for the GS, obviously, although it could be useful to have a LIRON clone with a Floppy Emu for hard disk images leaving the built-in controller available to connect a real 5.25″ floppy drive. Or to use two Floppy Emus at once.

    A SWIM emulator would be nice, but probably not quite as exciting. High Density floppies never really caught on in the Apple II world. I know I’d rather just use hard disk images with a Floppy Emu than use physical 1.44MB media. Physical 800KB drives are useful for copy-protected software that’s hard to image but I don’t think any Apple II software ever shipped on copy-protected 1.44MB media. (I can’t think of any commercial Apple II software shipped on 1.44MB floppy.)

    5.25″ controllers are probably the least exciting, as any II/II+/IIe you find on eBay is probably going to have at least one.

  2. Dillon Nichols - January 31st, 2018 5:14 pm

    That’s very exciting! I’d imagine many people would want both a Yellowstone and a FloppyEmu so you could use an easy cable between them and bypass using the hard-to-find DB-19. Are the original external drives still common and mostly functional? There might not be a huge need for only the Yellowstone but maybe the combination of your productions would be a hit.

  3. Jeff - January 31st, 2018 5:27 pm

    Fantastic! What about backporting the IWM core to the Plus Too? There’s nothing like running it on a different platform to shake out any remaining bugs.

  4. Leeland - January 31st, 2018 9:40 pm

    I’ve got to agree with even just a LIRON clone being something the community is calling out for. Evidence is we’ve seen them sell for huge amounts of money on eBay recently and people are asking even more huge sums for them now.

    I’ll personally buy at least one, if for no other reason than I think it would go so well with my FloppyEmu which I love.

    I also agree that the Super Drive controller would be cool, but the drives are hard enough to come by that it is of limited value and I don’t see it buying any extra functionality for use with FloppyEmu. And as has been noted, if there was never any commercial software released on 1.44M media, then there isn’t a lot of point. A FloppyEmu is a far better option these days.

    I’d be happy with just a floppy controller. Separate FPGA projects wouldn’t need to complicate this one.

    As I said before, I’m perfectly willing to buy a JTAG programmer if I need to in the unlikely event I’d ever want to update the card. Especially if it can work with one of the very inexpensive ones that have been discussed prior.

  5. Steve - February 1st, 2018 9:30 am

    Thanks for these perspectives, they’re very helpful. I’m leaning towards having Liron and Disk II functionality, selectable with a switch. No Superdrive mode (no high density floppies), no serial EEPROM, and no hypothetical “non-disk functions”. Keep things as simple as possible, so I can actually hope to finish.

    A Disk II controller mode isn’t very exciting by itself, but would make the Yellowstone much more versatile as a secondary disk controller in a system, or when used with Floppy Emu. Without a Disk II mode, you’d have to physically reconnect Floppy Emu to a different controller card whenever you wanted to switch between Smartport and 5.25 inch disk emulation.

    Eliminating any plans for a Superdrive mode would have many benefits:

    – Can downgrade the FPGA to a smaller and cheaper version
    – Avoids a difficult Superdrive-controller cloning task that I’m not sure I could do anyway
    – Eliminates most of the need for end-user JTAG reprogramming

    If I focus only on Liron and Disk II support, it’s less likely there would ever need to be firmware upgrades or bug fixes. The Liron and Disk II designs are 30+ years old and it’s unlikely I would ever “upgrade” them. Only the potential Superdrive and hypothetical non-disk functions really call for firmware upgrades. Without them, I would feel better about shipping a card without any simple way to perform end-user updates. But JTAG firmware updates would still be possible for advanced users with the right equipment.

    For anyone who wants to use a Yellowstone card *only* with a Floppy Emu, and doesn’t care about real disk drives, I could offer a version without the DB19-F cable. The Floppy Emu flat ribbon cable could be connected directly to the Yellowstone card without any DB19.

  6. LEELAND HEINS - February 1st, 2018 1:53 pm

    I’d like to see LIRON and VTech/Laser/CPS Universal Disk Controller modes… a card that was switchable between that would control about any commonly available Apple II drive. The Superdrive is just not common for Apple IIs, very few made. As I suggested over on FB, if you were to do a UDC (or Disk ][ controller as opposed to Apple 5.25″ controller) a second IDC20 connector would be cool so it could control two drives or a FloppyEmu and a drive or even two FloppyEmus.

  7. LEELAND HEINS - February 1st, 2018 1:56 pm

    Oh… I should have mentioned this before, but I don’t know if you’ve seen this before: IEC still makes and sells a bunch of Apple disk cables (they also have serial, parallel and game port cables for the Apple II). Not terribly expensive either.

  8. Steve - February 1st, 2018 2:42 pm

    I hadn’t even considered trying to clone any non-Apple hardware, so that’s probably not going to happen, sorry. What exactly interests you about the UDC card? You said earlier you didn’t really care about Superdrive. Maybe there’s some terminology confusion about “Superdrive” here.

    Apple only made three different 3.5 inch disk drives for the Apple II series that I know of: Unidisk 3.5 (A2M2053), Apple 3.5″ 800K (A9M0106), and Apple FDHD 1.44MB (G7287). Which of these drives is the one you’d hope to use with Yellowstone, that wouldn’t already be supported with the proposed design?

    A2M2053 is already covered by Liron mode, and nobody seems to care much about high-density disks and the G7287. 800K disks with an A9M0106 on the Apple II would require the Apple II 3.5 Disk Controller (aka the ‘SuperDrive’ Card), which is the thing I was saying would be difficult to clone and I’m not certain I could do it. I’d need to get my hands on one first to even begin to attempt it.

  9. Leeland - February 1st, 2018 6:19 pm

    The FDHD is the one normally referred to as the “Superdrive”. The UDC controls just about every Apple II floppy drive except the UniDisk 3.5 and the FDHD. It will control the Apple 3.5″ drive and Mac 400k and 800k floppy drives plus compatibles like the Chinon drives that VTech/Laser/CPS sold. The Mac floppy drives are often very cheap as are the Apple 3.5 Drives.

    FWIW, I don’t think the UDC is really that different than what is on the IWM. Most of the difference may just be firmware. You may already be closer than you think.

  10. Heny - February 2nd, 2018 3:40 am

    I’m curious about what is in the GS and IIc that can control the simple and cheap Apple 3.5 drives that the Liron implementation lacks.

    For many of us, the Liron card isn’t particularly useful if the only hardware you can connect to it is the Unidisk 3.5.

    Granted, I do suppose that smart port devices also qualify, your Floppy Emu being one of them, as well as other Smartport flash based storage systems like the UnisDisk Air from Nishida Radio (another hard to find item, sadly).

    The biggest unicorn for me is the Vtech Universal Drive Controller that can control a range of drives, and was a fairly simple piece of hardware.

  11. Roy Wood - February 2nd, 2018 6:29 am

    Nice work!

    It would be cool if Woz himself were aware of what you were up to. I’m absolutely sure he would be delighted…

  12. Steve - February 2nd, 2018 8:35 am

    3.5 inch disks all use double the data rate of 5.25 inch (1 bit every 2 microseconds instead of every 4 microseconds). That’s near-impossible for the Apple IIe’s 1 MHz 6502 to process in real-time, which is why the Apple II 3.5 Disk Controller (aka the โ€˜SuperDriveโ€™ Card) has its own on-board 6502 and 32 KB of static RAM for buffering.

    The UDC card contains a custom ASIC and static RAM that presumably do something similar, which you can see here: The UDC also doesn’t have an IWM or SWIM, so whatever they’re doing is totally custom.

    I don’t own either of those cards, and they’re fairly rare and expensive. But even if I had them, cloning either/both of those cards would be very difficult, as they’re much more complex than the Liron, and also contain custom ICs.

    The Liron card can be comparatively simple, because all of the hardware required for the fast data rate of the 3.5 inch disk resides in the drive, not on the card.

    The feedback from Facebook and here has mostly been that people aren’t really interested in a Liron card, unfortunately. So I probably won’t go forward trying to make this a product – too much effort for what would be a very niche product. It was fun to build, though!

  13. LEELAND HEINS - February 2nd, 2018 11:06 am

    That is the later version UDC with the ASIC. The early ones like I have were built with 74LSxxx and a few PALs. The card is much longer with quite a few more ICs and the IDC20 connectors on the end were along the top instead of the back edge. The early card is compatible enough with the ASIC version that the firmware is interchangeable. Reverse engineering the PALs could still be an issue because I’m sure the security fuses are blown. I don’t remember if those chips are socketed or not, I’d have to look at my card when I get home.

  14. LEELAND HEINS - February 2nd, 2018 11:06 am

    I’m pretty disappointed that may not happen, I think that’s unfortunate. Especially since it is so close to being done. However, I completely understand where you are coming from. I’ve gotten overwhelmingly negative responses on every hardware project I’ve proposed on the Facebook group. It is to the point where I’m pretty close to ready to give up on any idea of building anything as a product. There are a lot of people who seem to nay-say everything, sometimes even things that actually already exist. I’ve heard some even complain that the currently available products are overpriced (accusing some of “gouging”) or deficient in some way or things like that, which I think is awful. I don’t think most of these people understand the economics of all this. And despite the nay-sayers there are some Apple II products that actually seem to sell out pretty quickly when they are in stock, even ones like the A2Pi card and Uthernet II which many criticize as being bad products (which I think is unfair).

  15. LEELAND HEINS - February 2nd, 2018 11:07 am

    The current ridiculous asking prices for LIRON cards I personally think that despite what the malcontents say that there would be a demand for a clone. I’d think that if you could sell this for under $100 you’d sell quite a few and it may even sell a few more FloppyEmus if you can bundle it as a HD replacement too. People are lining up to order CFFA3000s, and the Yellowstone+FloppyEmu combination is a much closer competitor to that than the FloppyEmu is by itself. I’d guess the CFFA3000 will sell out quickly and this is likely to be the last run for 2+ years if ever due to Rich’s issue with obsolete parts forcing a complete redesign. That would put Yellowstone+FloppyEmu back to being one of the only consistently shipping flash storage options for the Apple II.

    Sorry I had to split this due to being long winded as usual.

  16. DFinnigan - February 2nd, 2018 11:30 am

    I have a UniDisk and I *am* interested in a Liron clone for it! Also if you could make the card compatible with Apple 3.5″ drive that would be good too.

    Forget that feedback on Facebook. There are over 1,000 people in the world who still care about and use Apple II, so go ahead and make the product. You are guaranteed to make sales. Especially if it is Apple 3.5″ drive compatible.

  17. Erik Olson - February 2nd, 2018 11:42 am

    Nice project! I’m going to check my Apple ][ collection to see what controller cards are in my IIes.

    I have experimented with the MachXO2. I know it says in the manual that the MachXO2 I/O can be set up to be 5V tolerant (internal diode, external resistor). That got meinterested in using it in a vintage computer add-on. I would be glad to hear if you investigated using the IO directly but found the LVC245 to be necessary.

    I am ultimately using ICE40 which is not 5V tolerant, so definitely using LVC245 for 5V bus tolerance.


  18. LEELAND HEINS - February 2nd, 2018 11:50 am

    I don’t have a UniDisk 3.5, I do have a couple Apple 3.5 drives and a couple of VTech/Laser/CPS Chinon based Mac compatible drives. I also have a UDC and a LIRON… but I still want a Yellowstone. If it would do Apple 3.5 drives, I’d probably want two or three… But I would like one for sure.

    If you don’t make it as a project I hope you’d at least consider releasing the Gerber files and the FPGA code so DIYers could build one themselves. Or even better the CAD files and the Verilog or VHDL source. I don’t know which CAD you use, Eagle, KiCAD or one of the others… or which language you use for developing FPGA code.

  19. David Schmidt - February 2nd, 2018 1:16 pm

    You spend too much time on Facebook. People snap up hardware for Apple IIs. If you build it, they will come. I want two.

  20. steveh - February 2nd, 2018 1:43 pm

    Aren’t Unidisk 3.5 drives extremely rare? That might explain the lukewarm level of interest. I suspect most A2 enthusiasts would want compatibility with the 800k Apple 3.5 drives, which I believe you said is not supported by this board. I have a couple of Central Point UDC boards (old w/ high parts count and newer with ASIC) and both work fine with Apple 3.5.

  21. Steve - February 2nd, 2018 2:42 pm

    > Sorry I had to split this due to being long winded as usual.

    Increased the max comment size to 8000 just for you. ๐Ÿ™‚

    > I know it says in the manual that the MachXO2 I/O can be set up to be 5V tolerant (internal diode, external resistor).

    That method can work, but it relies on the internal ESD protection diode which isn’t really designed for the purpose. I didn’t see resistor+ESD diode suggested anywhere in the MachXO2 datasheet, though I have seen it for other chips. For a one-off project, it’s a quick and easy solution, but I’m more comfortable using a real level shifter to get a robust interface. The 74LVC245 chips aren’t much more expensive than the resistor packs I would have needed anyway, so there’s not much penalty.

  22. Mark D. Overholser - February 2nd, 2018 2:55 pm

    I would be interested in a card for 3.5″ Apple Drives, but I don’t have any Unidisk Models,just the Apple3.5″ Drives..

    I would probably purchase One of these…


  23. Chris M. - February 2nd, 2018 2:59 pm

    Apple did make a card based equivalent of the IIgs and IIc+ disk port (card supports 5.25″, 3.5″, and Smartport all on the same port), they called it the “Apple II Universal Controller Card”. Problem is that its WAY rarer than even the Liron card.

    Here is the only photo that I know of, and its pretty lousy (I think the card is owned by Tony Diaz)

    Instead of a 6502, it likely uses the “Magic Glue Interface” chip out of the IIc+ to be able to read 3.5″ disks on a stock 1Mhz Apple II. Problem with that is there are likely zero docs out there to clone that chip in a FPGA.

  24. Todd Holcomb - February 2nd, 2018 4:11 pm

    I would buy one of these as well – I’d love to be able to run 3.5″ disk images on my Platinum IIe!

  25. Steve - February 2nd, 2018 4:21 pm

    > You are guaranteed to make sales. Especially if it is Apple 3.5โ€ณ drive compatible.

    Sorry to pick on this comment, but it exactly demonstrates my dilemma: this project is *not* Apple 3.5″ drive compatible. It cloned the Liron controller, for the Unidisk 3.5 and Smartport hard drives (including Floppy Emu’s Smartport mode). Although some people are interested in that, most commenters are skeptical about the usefulness of such a card. That’s fine – I wouldn’t try to convince anybody to buy something they don’t need – but I also can’t provide a magic Apple 3.5 drive solution I don’t have and I’m getting headaches from people repeatedly bringing it up. ๐Ÿ™‚

    I definitely agree a 3.5 inch controller clone would be a great thing. But I don’t have one to offer, and I’m not even sure how I would make one, due to the complexities I mentioned above. To even attempt it would almost surely push out the project’s finish line into the far future. It could be a “maybe somebody” feature, hardware permitting, but it’s just not something I can pursue right now.

  26. Tim Buchheim - February 2nd, 2018 4:35 pm

    I think there’s certainly a market for Yellowstone. Probably more as a companion to Floppy Emu than an actual Unidisk drive, as those are hard to find these days, but I would expect more people to be interested in disk images than actual 3.5″ floppies. And right now a LIRON + Floppy Emu is one of the few viable ways to use disk images on a IIe or earlier. (The other one is the CFFA3000, but the supply of those is about to dry up.)

    Can the Floppy Emu in Smartport mode make 800 KB disk images look like a Unidisk drive? If so then Yellowstone would serve the needs of those looking to use 3.5″ disk images on a II/II+/IIe, even if it can’t work with physical drives other than the Unidisk.

  27. Tim Buchheim - February 2nd, 2018 4:37 pm

    Oh, btw, I was poking around looking for some other stuff and happened to run across this trove of old IWM/SWIM documentation (and other interesting floppy-related stuff that was meant to stay confidential inside Apple):

    Nothing jumps out at me as being immediately useful to you, but there’s certainly some interesting reading there if you haven’t already seen it. ๐Ÿ˜‰

  28. stynx - February 3rd, 2018 12:41 am

    I have several Liron Controllers but I think the Yellowstone card will be very cool! A nice generic FPGA card is cool in itself especially if you can offer it at lower than $100. The possibility to add generic SPI Hardware to the mix could allow for more flexibility in the future.

    Keep up the good work!


  29. stynx - February 3rd, 2018 12:54 am

    I just wanted to add that I can offer to give you 2 UDC (older and newer version) as well as the BlueDisk (1.44mb MFM Controller) and the ERPHI controller (another MFM controller). I would offer these cards as either unlimited free lease if you are interested or they can be gifted.

    My offer to support the development of the Yellowstone:

    1x older TTL UDC
    1x newer ASIC UDC
    1x BlueDisk
    1x ErPhi

    I can look in my boxes for more drive cards and add them to the mix ๐Ÿ™‚


  30. Ian - February 3rd, 2018 8:11 am

    I’d buy one. I hope you make a run of them!

  31. macnoyd - February 3rd, 2018 8:56 am

    I’d also buy one when they are ready. Nice work!

  32. yesterbits - February 3rd, 2018 11:12 am

    I second the idea that it would be useful paired with a Floppy Emu more than anything else, though I have a few UniDisk 3.5s and actual Liron cards. I’d most likely install these in Apple ///s, I’d certainly buy at least one myself.

  33. Wayne Stewart - February 3rd, 2018 11:36 am

    Looks interesting. I have quite a few Liron cards so I don’t really need one but I’m tempted anyways

  34. Steve - February 3rd, 2018 11:45 am

    OK, maybe there’s more interest in the Liron / 5.25 functionality than I thought. I’ll keep playing with it regardless, and see how close I can get to “product ready”. Jonas, thanks very much for your UDC offer and I’ll probably take you up on it, once I’m ready to look more at other disk controller types. A few people asked about price and timing. Both are hard to estimate when I’m not quite sure what hardware or features would be on the finished card, but I would guess under $100 and maybe 2-6 months depending on features and my productivity.

  35. stynx - February 3rd, 2018 1:56 pm

    I normally use only the CFFA 3000 in my main A2s but I do this only because I cannot use up too much slots. I would like to be able to connect a 3,5″ and a 5,25″ Floppy without taking my systems apart and removing cards to do so. If you were able to add a basic hard disk feature from SD card, I would most likely replace the CFFA in my A2e. If you were able to integrate basic FloppyEmu functionality into the Yellowstone as well, I would pay much more than $100 for sure!

    Contact me for the shipping of the cards as soon as you need them.


  36. Jason - February 3rd, 2018 7:07 pm

    I have a 2e and a 2c+ and I want to be able to move data & programs between the two.
    I need either a 3.5″ drive on the 2e or a Smartport on the 2e & a Floppy Emu.

    A Yellowstone and a FloppyEmu would work perfect (especially if I could connect my 5.25″ drives to it as well !!)

    If you ship the Yellowstone, then I’m all in for one and a FloppyEmu !


  37. Austin C Phelps - February 3rd, 2018 8:02 pm

    I would be interested in a Liron card.

    Would the code and designed be released?

    Keep up the good work.

  38. Jorma Honkanen - February 4th, 2018 10:02 am

    I hope the card comes out, it is really needed one.

  39. Eric Smith - February 4th, 2018 6:26 pm

    The Apple 3.5 Controller (aka SuperDrive Controller) does have a 6502, but the only thing particularly complex on the card is the SWIM (as compared to the IWM). I spent some time reverse-engineering most of the 3.5 Controller firmware a few years ago.

    If I were implementing this in an FGPA myself, I might not try to reproduce the SWIM, but just use the IWM implementation you’ve already developed, and add an implementation of the 1793 to support MFM. I’ve got a partial 1793 implementation in VHDL but have more work to do on it. Of course, the 6502 code in the firmware to support MFM would then have to change.

  40. Tom Leung - February 9th, 2018 1:46 am

    Good to see someone is working the FPGA project like this.

    I would like to get one if the card is ready for production.

  41. Jean-Claude MICHOT - February 23rd, 2018 9:25 am

    Just for LIRON clone, i’ll personally buy at least one.
    Smartport hard drives with Floppy Emu’s is what i need.

  42. Andrea - March 9th, 2018 2:13 pm

    Incredible work Steve! you spent less time in creating a new liron card from scratch, than me in repairing the original one i got! LOL

  43. Andrea - March 10th, 2018 2:21 am

    And i want to add my personal point of view on the development of the project. I bought Floppy emu and I will buy, I hope, Yellowstone, and we would wonder, as our wives and friends probably do: why?
    The answer for most of us I think would be to relive those moments, breathe a piece of history, appreciate the jewels that few now know how to recognize.
    A card that adds 4k high resolution or can read ntfs files with Apple IIe? Everything could be done, but who would want it? Those who want a powerful and versatile computer can buy a MacBook I7 or a Windows 10 system!
    For months I torture my Asco Liron in an attempt to resuscitate it .. because I am a collector, because I am a nostalgic, because I was a geek ante litteram …
    Steve has done an incredible job in replicating the Liron, and in a very short time: I really hope he can share his goal with us in some way, and I close by saying how I would like the final product: with the same form factor as the original Liron, same green vintage, maybe even with an external 4k eprom with the original Apple Rom! Maybe I’m getting old …

  44. Chris M. - May 7th, 2018 6:46 am

    Just an FYI, but it looks like ReactiveMicro is preparing another run of their Superdisk 3.5 controller clone.

    Don’t know where they are sourcing ICs like the SWIM chip, but the price shows that cloning that card is not a cheap endeavor. The price of their TranswarpGS clone is even more eye-watering. If there was a card ripe for FPGA cloning, its that one.

  45. Steve - May 7th, 2018 7:15 am

    I think it’s great they’re making a Superdisk 3.5 clone again, although I’m a little confused by the approach. From the photos it looks more like an exact replica of the original card using vintage 80s components, rather than a functional clone. I asked Ultimate Micro about this a year or so ago but didn’t get an answer. My guess is the SWIM chips are coming from salvaged IIgs and Macintosh motherboards. The photo of the card shows lots of socketed PLCC chips, and even a socketed DIP EPROM, which maybe could be replaced with newer and cheaper 2018-era parts.

  46. Mike - June 30th, 2018 4:43 pm

    Personally, I would like to see a clone of the SWIM. Mainly for repairs and modding in the Mac world. I am quickly running out of replacement SWIMs for repairing fried ones on the mac portable, so an FPGA programmed as a SWIM and making an adapter board to PLCC would solve that problem.

    And then of course I would like to add SWIM/HD support to the Mac Plus because why not?

  47. Joshua Bell - August 19th, 2018 9:33 pm

    Just piping in to express my support for productizing. I’ve got a //e set up for my son and would prefer to use a Floppy Emu as it’s solid state storage mounting disk images as smartport hard drives, as I do on my Laser. Swapping SD cards around and updating images using emulators is very convenient. With Liron support (or even just the dedicated FloppEmu version) I’d be set, and order two (plus another Floppy Emu)

  48. groinksan - August 21st, 2018 12:05 am

    I second the endorsement for continuation on working on this project. I have a Unidisk 3.5 and would love to use it on my IIe which is my primary computer.

  49. groinksan - August 21st, 2018 12:26 am

    One other thing to mention…. You’re asking for recommendations for other disk controller projects. My all-time favorite disk controller happens to be what is called the Prometheus “Applesurance” which is a disk controller that not only boots 16-sector disks, but it also does a full diagnostics of your Apple II, by checking RAM and ROM, among other things. Since your card is booting the computer, might as well have it do other tasks in the process. The user can disable diagnostics and boot only by holding down the space bar during booting. My Applesurance card also supports only the II/II Plus, since it was made before the IIe ever existed.

    Another disk controller to look at is the MicroSCI disk controller, also known as the Franklin Computer disk controller. The reason I like this card is that you can move a jumper between 16-sector and 13-sector boot support. I have one card that actually does this without jumpers, but it crashes when booting ProDOS.

    Personally, the Disk II controller is not worth cloning. There’s way more than enough of this card around on eBay, selling on average $15 each. I have about 20 of these myself. Same with the 5.25 disk controller – it is virtually the same as the Disk II controller but with a different disk drive connection.

  50. A - September 14th, 2018 1:49 am

    Making the EEPROM functional if its still there on the card should be to much additional work, says someone thats a complete weekend hacker at hardware, and would make it more useful for someone without other mass storage devices.

  51. Anthony Adverse - October 16th, 2018 10:32 pm

    Hey there,
    Hows the status on this? And how far away are we from a publicly available card? Just think like, Jimmy Neutron…. keep moving forwards…


  52. Greg - November 30th, 2018 10:08 am

    Just throwing another vote behind this project. I already own a Floppy Emu and I have an odd use case: I accidentally blow up my IWM on one IIgs, which otherwise works perfectly. So….I have a rather limited 5.25″ controller card in there right now and can no longer use the Floppy Emu or 3.5″ drives. Basically it’s relegated to a high-speed IIe. Definitely like the idea of this card as a swiss army knife: (1) Make the IIgs workable or (2) add functionality to my actual IIe or (3) act as a fancy bridge card for my Floppy Emu.


  53. Nate - April 3rd, 2019 11:13 pm


    I was wondering if you are still considering to produce this card.

    Some ideas you may want to consider doing to make it better and useful:
    1. Add a port that can accept a cheap RTC card such as the KEYES DS3234 ($5 or less on eBay)) to have a Real Time clock card (these are rare these days).
    2. A combo serial and full parallel port (so the parallel port can be used as IOs).
    3. A GPIO port, I think it will be cool to be able to write basic/assembly programs on the A2 to control/monitor stuff instead of using an Arduino.



  54. Ken - June 30th, 2019 2:28 pm

    Hi Steve – I, too, am wondering whatever happened to this project? I don’t see it listed in your store so obviously you have not manufactured any for sale. Do you plan to?

  55. Steve - June 30th, 2019 7:23 pm

    I never found a resolution for the occasional bus interface problems that were described in later blog posts, then I lost interest and moved on to other things. I released the design as open source earlier this year, in the hopes that someone else might pick it up.

  56. Micheal Fields - February 11th, 2020 1:46 pm


  57. Franck - April 10th, 2020 3:44 am


    What a very great job, I hope you have a kit to sell.
    I will buy two pieces

    Best regards

  58. Antoine MERCIER - July 28th, 2021 7:34 am

    Wonderfull work !

    I was wondering if this work was usable as a start to make a sort-of usb adapter for old apple floppy drives using an Arduino shield or by making a Raspberry Pi HAT … (maybe I’m not very clear … sorry, I’m french and my english is “rusty”)

    The goal would be to connect an old Apple floppy drive on a quite recent computer using usb.
    I know about AppleSauce but their solution is so expensive and not exactly what I’m thinking about.

    Thanks for your answer ! ๐Ÿ™‚

  59. Steve - July 28th, 2021 3:24 pm

    Aside from connecting to disk drives, Yellowstone is not very similar to what you’re describing. If you want to use a microcontroller or Raspberry Pi to bit-bang control signals for Apple drives, you could look at the Disk II ROM disassembly combined with the IWM spec: That would show you how to find track zero and read a sector.

  60. Rob N - October 31st, 2021 6:34 am

    Put me down for one of these. If course, there has been no feedback for building these as a product. I see that no one has actually bought one, so I guessed it’s a busy product. There actually is a market for these, albeit perhaps a small fan base market. Nevertheless, this product should not go to waste. Please MARKET IT!

  61. Steve - October 31st, 2021 7:47 am

    Please see the ongoing Yellowstone development discussions at It’s currently (October 2021) in limited beta testing, and hoping to have general availability in a few more months.

  62. Mark Mathosian - November 27th, 2021 12:56 am

    All I can say is, โ€œI want one.โ€ Lol Ready to buy when this great Apple ll product is ready.

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