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SuperSVGA

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  1. For something in production, you could try the TL2218-285PWR. I personally use the DS21S07AE (NOS) because I can find it for cheaper, but it requires a few extra capacitors.
  2. I've assembled a few but haven't been able to test, because unfortunately neither of my LC power supplies seem to work (even after recapping them) in either of my two LCs. I think the only other computers I have that take VRAM SIMMs are a Centris 610 and a Duo Dock, so I'll have to get one of those out if I can't get a power supply to work. One thing I noticed is it seems like there's a slight dimensional accuracy issue in the SOJ40 footprint, or it's just a mistake from the cheap PCB manufacturer I used. As you can see in this picture, it just barely doesn't line up right:
  3. The PCBs finally arrived, now if only the capacitors I had ordered before the PCBs had ever shipped... Oh well, I suppose they might be fine without the capacitors. So, what tests should I run on these besides just sticking them in and seeing if it goes?
  4. I actually had forgotten that the Portable doesn't have termination power. On the Macintosh Plus it's an easy fix, you can add a diode to an unpopulated spot on the logic board and it provides termination power, but I don't know if anything like that exists on the Portable. The only concern I see would be that power might go into other devices in the chain if they accept it, potentially drawing more power out than desired, but the draw from other devices might not be significant enough, I guess it really depends on what you hook up. SCSI spec says provided current on term power
  5. Here's what I threw together. Probably works, but feel free to make any corrections. Here's all the files: https://github.com/SuperSVGA/VRAM68/tree/main/VRAM SIMM TC524258BJ v1.0
  6. Which chips are you looking at getting? I can put together a quick design, and then you can modify it if needed. I've already got a few designs, but they tend to vary based on chip.
  7. Mouse input should be relative, not absolute. I believe the mouse typically provides X direction, X speed, Y direction, and Y speed as input. The Atari controller however provides each direction more like a button, so one for each of the four directions.
  8. MacTest definitely runs on the 68k, it goes back pretty far. Make sure you have the right version.
  9. I don't suppose you've tried starting up without loading TCP, selecting Restart from the Special menu, and then using TCP? You could also try running MacTest, I remember that having a few useful diagnostic tests.
  10. Here's one I found claiming to be from a Mystic Color Classic: https://www.worthpoint.com/worthopedia/512kb-68pin-70ns-vram-simm-selected-1806282637 They have two TC528257J-70, which should be 2Mb/256Kx8 70ns chips. Here's another http://web.ncf.ca/bj151/mac/mac-ram/68pin-512k-vram-simm.html This one is similar but with 80ns chips.
  11. I'm seeing some images online of 2 chip 512KB SIMMs claimed to be pulled from Macs, so it definitely sounds possible, but it's also possible not all models support them.
  12. Maybe for just a few, but PCBs are so cheap and let you skip the time it takes to remove the old chips and clean them up, plus it leaves more 256KB VRAM SIMMs in the world.
  13. There's still a decent selection of NOS Video DRAM chips around, so building your own probably wouldn't be too difficult.
  14. If the error is to be believed it's bit 18 of bank B. For future reference: Example: $AABBCCDD AA=8 bit mask for bits 31-24 BB=8 bit mask for bits 23-16 CC=8 bit mask for bits 15-8 DD=8 bit mask for bits 7-0 So with your code of 00040000 and with the masks expanded, it looks like this: 31 0 00000000 00000100 00000000 00000000 Maybe a scope or logic probe on the address lines might show you something? Here is the memory page of the schematic:
  15. Well the greater issue I see is that each client contacts another client, so everyone connecting needs to be reachable by everyone else. All the client’s would have to have a compatible networking setup, but possibly you might be able to get around this with an advanced relay to rewrite the packets and port forwarding on each client. Although NAT is part of the issue saying it’s just NAT doesn’t really get us to the right point. I’m guessing the important part is finding out how it interacts with Port Address Translation(PAT)/NAT Masquerade, and if Source NAT might be part of the solution.
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