WOOOOO! Floppy Emu’s last big goal has been reached, and 1.4 MB disk emulation is now working! The photo shows a Mac Classic, booted into System 7.0 from a 1.4 MB high-density disk image. Combined with other recent improvements, this…
After nearly a year of inactivity, I’ve started work on Floppy Emu again! One of my first priorities was compatibility with Macs that have a 400K floppy drive – the original Mac 128K, and the Mac 512K (not the 512Ke).…
After fiddling with Nibbler’s hardware and fixing its glitches, it’s time to write some demo software. Let’s see what this little handmade 4-bit CPU can do! Sorry the quality on these videos isn’t the best – try changing the quality…
It’s time to shop for a new oscilloscope. My trusty HP1631d has served me well, but it’s almost 30 years old, and it’s not even really an oscilloscope but a logic analyzer. This boat anchor is big, heavy, loud, cumbersome,…
What happens when you feed an invalid voltage level to the input of a digital logic gate? It’s an interesting story. In my last post, I described a subtle Nibbler bug where a combinatorial feedback loop through the ALU caused…
Aha! After four days of tinkering with Nibbler, I finally found the cause of the occasional bad writes to RAM. At first I thought it was a timing problem with the RAM enable signals, then I thought it was bus…
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