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Picked up a Lisa for testing and evaluation and questions to follow

I'm curious what you are doing. At first you had the machine running, then you started debugging the profiles, then you started checking the ram and now you are checking the video memory. I've never run into a lisa where after years of no use it would suddenly start failing a whole bunch of components.
 
Hi @NeXT. FYI It was a different Lisa! In one of my previous posts I mentioned that we found 3 more Lisa's! I am in the process of checking out another one.

So maybe I should have started a new thread?

Anyway It wasn't the video RAM it is a Lisa with the screen mod. When trying to boot Lisa OS 3.0 it had a bad screen image. So I had assumed it was bad video memory. It was not. So it was my mistake. The ROM version in this Lisa is 3A/A8 for those that are curios. Mine has H ROM

Oh and It runs fine BTW.

Hence the messing with the profile drives RAM etc. I am using my Lisa most of the time as a test bed. So there will be more to follow.

Explains the corrosion removal thread elsewhere.
 
Chromedome45 said:
Anyway It wasn't the video RAM it is a Lisa with the screen mod. When trying to boot Lisa OS 3.0 it had a bad screen image. So I had assumed it was bad video memory. It was not. So it was my mistake. The ROM version in this Lisa is 3A/A8 for those that are curios. Mine has H ROM
Click to expand...

If you desire to do so, the screen mod can be reversed. I did it to a Mac XL so the machine would be capable of running Lisa OS, since 3A ROMs only let you run MacWorks, which isn't that exciting when Mac Pluses are a dime a dozen. You just replace the 3A ROMs with H ROMs (They are standard UVEPROMs, type 2764 8K x8 ), replace the video state machine ROM with a Lisa one (they can sometimes be found on ebay, you may also be able to find a blank ROM and program it yourself but they're a little harder to find than a 2764). There's also an inline transformer on a cable between one of the CRT yoke cables and the video board that has to be removed. After that it's just a matter of readjusting the pots on the video board.
 
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@lroop I was under the impression that even with the 3A ROMs all you needed to do was replace the character generator ROM to run Lisa OS. Which ROM is the state machine?
 
Chromedome45 said:
@lroop I was under the impression that even with the 3A ROMs all you needed to do was replace the character generator ROM to run Lisa OS. Which ROM is the state machine?
Click to expand...

I'd assume the ROM you're calling the "character generator" is the state machine. IIRC the Lisa doesn't have a character generator, it's a bitmap machine. The ROM in question is Apple P/N 341-0229, it contains some video timing data as well as the Lisa's serial number (this is how the 'copy protection' in the Lisa OS knows what machine a tool disk was originally used in). It's an odd ROM, 256 bytes with tri-state outputs (The one I have laying around not in a Lisa is a TI TBP28L22N). I think the Disk II controller card used a similar type chip but these are one-time programmable chips.

As for whether or not Lisa OS will boot on 3A ROMs I'm not sure. I read years ago that it will not, but have never actually tried it. I think I have a set of 3A ROMs left from a screen mod kit I pulled out of a Lisa, maybe I'll try it sometime and see what happens.
 
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