hkz3d ago

Some bodging to rectify my fuckup and...
The MiSCUSI (#Apple2 #SCSI card) works!!!

Which means that I just need some minor rerouting and I can get ready for a rev.1 release. And then for a 53C80 (MUCH easier to obtain) release too!

Show threadhkz3d ago

The MiSCUSI and its bigger brother: the FoxSCSI by @DosFox

They're fundamentally the same card.
I have to say, I still like THT cards better for an #apple2 , but the MiSCUSI should be cheaper if someone wants it assembled in fab. Might have to look into replacing the 74LS133. It's expensive.

Show thread🇺🇦 haxadecimal 🚫👑1d ago
@hkz @DosFox
I've been sad for a long time that the 74LS133 was discontinued. It was great for Apple II cards to detect access to $CFFF to reset their expansion ROM enable flip-flop.
Show threadhkz1d ago

@brouhaha @DosFox yeah... You can use an ALS133, that seems to be still in production.
But still expensive.

And the thing that bothers me is that I did not find a solution using jellybean logic that takes less than 3 ICs.

I could use a PLD, but then we get into ridiculous territory.

Show threadDosFox16h ago

@hkz @brouhaha if you use a 74ls10 and a 74ls21, you could build an 11 input NAND, which would be enough for the apple ii SCSI card.

The apple ii is also slow enough that propagation delay might not be an issue

Show threadhkz16h ago
@DosFox @brouhaha true! I'll design a variant with that. In any case I could switch one to an 'F
Show threadDosFox16h ago
@hkz @brouhaha ah that's true! Could always knock one together on some Veroboard, and stick it into the FoxSCSI
Show threadhkz
@DosFox @brouhaha or one could tweak the cap at the output. It's there to delay the output I guess.
4:50pmWeb
Show threadDosFox16h ago
@hkz @brouhaha hah of course!