I warned you I was bad at documentation

A project log for A Brand New Apple Lisa

Producing a Functional Clone of the Apple Lisa 2/5, using NOS components.

dosfoxDosFox 11/26/2023 at 20:380 Comments

Yeahhhhh, I did say I'm not great at documentation. 

But before I completely forget, here is a quick run down of things I found during building the Lisa. 

1) On the CPU board by Warmech, there is a capacitor at C43. On an original Lisa, this was a capacitor that bridged over U5C. This capacitor is a 47pf ceramic through hole capacitor. 

2) For some insane reason the keyboard interface needs a 3.3K pull *down* resistor, despite already having a 3.3K pull *up* resistor. I'm at a complete loss as to why this is needed, but alas it is needed. The keyboard interface only partially works if the 3.3K resistor pulling it to ground is missing.

3) Most 74S logic can be replaced with 74F logic - F logic is a lot easier to find, and a lot cheaper than S logic. I avoided HC and HCT logic like the plague - so use the wrong family as sparingly!

4) The 6309 PROMs can be replaced with 82S135 PROMs, or 82S147s - so long as you tell the programmer to treat the 82S147 like a 82S135! Alternatively, a W27C512 to 6309 adapter can be made, and has been proven to work.

5) gerbers for a 2mb ram card now exist! This has been built and tested in the clone - the Apple Lisa is now 100% not from Apple! It's also worth noting that there is a slight issue with the silkscreen - R1 and R2 are 33 ohm resistors. The resistor network at RP3-RP7 are 33 ohms, and are ISOLATED. I made a mistake and used bussed resistors, which didn't work at all. This is also a bit touchy about which TTL families are used, so definitely use the suggest 74S and 74LS ICs on the 2mb card.

Also the only RAM sticks that work are 256kb parity (either 9 or 3 chip sticks) at 12ns or quicker. 80ns will work, but then it'll crash after a few minutes. You sadly can't get away with loading two 1mb sticks in memory bank 1. 

6) The ArduinoFile (profile emulator) has been tweaked/improved. The arduinofile now no longer errors out with a timeout issue, and has proven to be pretty damn reliable. It should also work in a Lisa 2/10 which has a quicker hard drive interface.

7) The Lisa LITE is only needed for 400K floppy drives. The LITE only generates a PWM signal from two other signals. The Floppy Emu and 800K drives (which can be used in place of a 400k drive - try it in your Macintosh 128/512k!) do not need this signal. Therefore a passive adapter can be used instead.

8) There is now a python script to split out a ArduinoFile Image so it can be mounted under Mini vMac. It can then recompile the drive image for the ArduinoFile. This makes copying Macintosh Files incredibly easy now:

It's a little bit funky, but it's incredibly effective.  

9) A full Lisa can now be built from "only" 5 major boards (six including the COP adapter, seven including the external arduinofile):

COP Adapter Gerbers (bottom of the page):

CPU and RAM Card Gerbers:

Motherboard and IO Card Gerbers:

ArduinoFile Gerbers:

Front Panel PSU/Power Switch/Keyboard Interface:

(Note to self, get these on the Internet Archive with the ROMs.)