Schematics for Power Mac 7600?
- Thread starter Byte Knight
- Start date
Phipli
Well-known member
Folks searching, please not this 6500 schematic also applies to the 5500 and the TAM.
Looks like the Gazelle was designed with fitting a 604 in mind (sadly no mention of the 604ev, so not sure if it can provide the power needed or what other differences there are). There are a few "no stuff" components that are labelled as being for 604. Also there are details on how to set the core voltage for the CPU in the schematic.
I always grumble about these machines having quite a capable graphics chip, hobbled by only 2MB of VRAM... Glad to see they didn't ship with the 1MB option they considered! It does flag the additional CAS and RAS lines on pins 28 and 206 of the ATI chip though if anyone feels like stacking SGRAM to get 4MB and more QD3D games running.
@dosdude1
Looks like the Gazelle was designed with fitting a 604 in mind (sadly no mention of the 604ev, so not sure if it can provide the power needed or what other differences there are). There are a few "no stuff" components that are labelled as being for 604. Also there are details on how to set the core voltage for the CPU in the schematic.
I always grumble about these machines having quite a capable graphics chip, hobbled by only 2MB of VRAM... Glad to see they didn't ship with the 1MB option they considered! It does flag the additional CAS and RAS lines on pins 28 and 206 of the ATI chip though if anyone feels like stacking SGRAM to get 4MB and more QD3D games running.
pizzigri
Well-known member
interesting. I may have the SGRAM chips on some old ATI board for PC, I could piggyback them on- would that possibly damage the board?
Phipli
Well-known member
It would be delicate work, you'd be picking up pins from the ATI chip and being SMD, piggybacking would be... tricky.
Technically it is possible. I just wish they'd put a SGRAM SODIMM socket on the board like on the beige G3.
I may be inappropriately bumping - and feel free to tell me off - but I'm trying to track down schematics/boardviews for an 8500. I have a board that's received extensive corrosion from a battery leak - and leading to the vias directly under the battery being unusable (and they appear to be heading off into multi-layer land).
GRudolf94
Well-known member
Unfortunately boardviews really are a modern mac thing only. There's 9600 schematics attached earlier in this thread and that would be of some use, but it'd still be a lot of wandering around in the dark to use that to fix corrosion damage on an 8500.
It's going to be very challenging. I'm trying to source another 8500 board now - which may or may not help. I'd rather not let this other board just go in the scrapper if I can help it. The corrosion is limited a small section, just very deep into those multi-layer vias.
Thanks for your assistance.
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jajan547
Well-known member
Can you post some photos in a new thread would be easier to assist
I'd be happy to - but it depends if anyone finds it interesting. I'm just some random Aussie with a love of old macs and restoring retro gear.
jajan547
Well-known member
yeah go ahead upload some photos worst case I can send you a spare board
GRudolf94
Well-known member
Never! Most junk boards are worth keeping around, just in case you get something with a mangled ASIC or some other missing component down the road.
It would more go on my 'scrap parts' storage bin rather than an actual rubbish bin. There's always value in this stuff.
I've isolated the issue down to 8 traces/vias which all seem to relate to the Hammerhead IC (opposite side to the battery).
I've been clearing out vias of their corrosion with small PCB drill bits to prevent further damage. I've also managed to track down a very worrying looking vias and confirmed they are working.
The 9600 schematic gives some idea of how things should be laid out, which is better than nothing.
I should take some more photos and upload to it's own thread.
With a bit of luck, a better condition 8500 board should soon arrive, which should mean I can trace down anything I'm unsure of, and repair it.
I wish this had been as easy on the 6360 board I have in my 'too hard, later' pile. I really need an Ultrasonic before I think it's worth going much further on it (it apparently spent many years in an open area, and is literally caked in dirt under ICs, etc).
Kind of a necro, but what the heck...
Do you think the Samsung KM4132G512Q-10 would work for this purpose? I have a couple thousand of them... However, they're 2MB, 256K X 32 X 2, which is 2MB, not 1MB. So might be a drop in replacement if the address lines are there, or if the originals are single banked, perhaps the CAS/RAS could be massaged to provide bank signal.
Hmmm. Okay, looked at schematic. The originals are 256K X 32 X 1 with minimum -10 speed. So one could probably jsut solder them in place and rig some logic from the RAS/CAS's to the Bank signal pin. I haven't looked at the timing diagrams, so I'm not sure if you'd need some kind of buffer to hold one or the other for the entire transaction or if they stay active for the same time periods....
Okay, so I was further examining the pinout on the schematic, and it looks like there is a BA pin and it is connected to MMA[9].
That suggests that one could simple drop these chips in and they'd have all the hardware support they need. Does the ATI chip auto-detect the VRAM present, or would some kind of firmware mod be needed?
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