Grendel's 65c02 Mod for the AppleII & AppleII+

The information on this page is purely experimental, anything you screw up on your hardware is your problem, not mine. It is expected that if you are reading this that you know what you are doing. Do NOT write me any messages saying you blew up your apple, are in the hospital with electrical burns, or are suffering from zinc fever. If you aren't smart enough to work in a well ventilated area, with a computer thats turned off, and a cover over your apple's powersupply to keep solder from getting into it, then go elsewhere, I cannot help you with your problems.

    I've recently dug out my AppleII+ from the pile of stuff hiding under my computer desk, and have decided to build an IDE adapter for it, one problem though, all the IDE adapters I've found use 65c02 instructions in their drivers. Not one to rewrite gobs of 6502 asm, I've instead gone on a quest for knowledge regarding 65c02 mods for the AppleII.

    My quest lead me to the archived Apple Assembly Line issues once hosted on GEnie, now on the Apple II Public Domain File Archive. In the artices I found there, a few methods were described for sqesszing a few extra nanoseconds (yes, nanoseconds) out of the circutry so that the 65c02 can get data from the system within the spec'ed times. I also found some old hand written notes (presumidly from my father who was going to do this mod himself long, long ago) about methods 1, 2, & 3.

    I will go on to describe a few of the methods I found, some of these techniques may even be used to get a 65802 or 65816 to work in the Apple II & II+.

Option #1

Handwritten Notes & AAL Dec 1984 : IIPlus.65C02 by Andrew Jackson
    Upgrade B6 & B7 with faster versions
Remove the 74LS257's at B6 & B7.
Replace them with 74F257's.
That wasn't that hard was it?

Option #2

Handwritten Notes
    Upgrade B5 & B8 with faster versions
Remove the 74LS174's at B5 & B8.
Replace them with 74F174's.
This should be used with #1 if #1 is not enough.

Option #3

Handwritten Notes
    Piggybacking the 6502 /0 clock input with a 74LS08.
Bend up pin 3 on the IC at B11.
Flatten out all pins on the piggyback IC except VCC & GND.
Tack-solder the VCC & GND of the piggyback onto the VCC & GND of the lower IC.
Connect 1, 2, 3, or 4 gates of the piggy back IC in series between the lower IC's pin 3 and the socket's pin 3.
Only connect enough gates to get the system to work.
This should be used with #1 & #2

Option #4

AAL Oct 1985 : Another65C02Fix by William O'Ryan Jr
    Substituting AX for /RAS.
Bend up pin 9 on the ICs at B5 & B8. (74LS174)
Solder a wire to pin 14 of the IC at C2. (74S195)
Connect this wire to pin 9 of the ICs at B5 & B8.
THis probably should not be used with #1-3.

This page copyright (c) 2002 by DCGrendel.