This is curious: @iconicbits also has a SunRem 2MB card that hasn’t worked either. And combined with an Apple 512K card, was also able to produce an error 45.
It seems the Lisa thinks it only has 128Kbytes of memory, according to these memory locations ($294-297 maximum physical address and $2A8-2AB total memory). Need to look into the boot rom to see how memory size is determined.
If I understand this correctly, memory $282 should hold the address that caused the bus error. In my case, I get
282 0002 0000
which I think is $020000 (high byte is ignored). Does that mean the problem is occurring at position 128kbytes in the RAM card? Not sure how to map that to a component/components yet.
Ok, display sorted out, now to the next big hurdle. The #AppleLisaClone is throwing a error 45 which is a “bus error” and it happens as soon as RAM is being tested. So, @DosFox and I suspect the issue lies on the new RAM board.
I’ve tested the SIMMs in a Mac Iix and they work. I’ve also pulled all of the TTL chips and they tested good on the Chip Tester Pro.
Kinda stuck at this point. Having another RAM card would be very useful now.
Thanks to @48kRAM for the tip on wiring the Lisa to a RHB2HDMI (use the monochrome analog YUV connector (shield to pin 1/GND, video to pin 4/V). I’ve got a picture, but I hope to be able to improve this as the halftone pattern really rings.
Anyone have experience with the RGB2HDMI project (based on a RaspPi)? I’m trying to figure out how to use it with the #AppleLisaClone to get a better video out. I see it’s supported but I can’t find a wiring diagram.
So when you combine all of these things together, the #AppleLisaClone has shown the first stable screen and begins to do the self test!! Signs of life! This is a huge step forward.
Many thanks to @DosFox for the guidance along the way!
Next, I designed a board to plug into the #AppleLisaClone motherboard that breaks out the keyboard jack, power switch, power LED, and floppy drives. This powers on the Lisa as expected!
Probing pins 1 and 2 of the COP402 (which are the clock pins) I'm getting just high and no pulsing. Does the issue lie with the COP402 microcontroller or with the crystal circuit (which is on the IO board)?
The COP421 emulator is powered by +5v standby to manage time of day and soft power functions. At the PSU, it measures 5.3v. At the COP421 emu, it measures 4.7v. This is still in range of the COP402 (4.5 - 6.3v). My PSU delivers 1.8A of +5v standby.
Artist exploring vintage plotters with modern code. Retrocomputing repair and collecting. Mixes the best of new and old. He/him #plottertwitter refugee #penplotter #c64 🏳️🌈