4400/7220/Tanzania Clone VRAM

So from what I've gathered, the ubiquitous 2 MB (slow) EDO VRAM DIMM is so slow that going beyond the 2 MB is pointless. The upgrade was a 4 MB SGRAM DIMM, which I have yet to find in the wild—probably long-gone. The repair manual mentions other values as well, for both configurations, of 1-4 MB, which is interesting.



What I'm wondering is this: can one desolder the EDO VRAM and install SGRAM ICs in their place? I can't find a p/n for the SGRAM that was used contemporaneously, or even what to look for as far as specifications to accomplish this. Also, I wonder if this is a dead-end simply because of the arrangement. Now, this is all coming from a non-engineer, so forgive me if I'm way off base. I managed to find what I think are images of the SGRAM DIMMs, and they look much different (the packages are different?) from the 2 MB DIMM:
 

This one from MemoryTen (vs Memoryx, yet the same company??) but though it shows it in stock, you try to add to cart and it gives you a sorry message.



This one was from a google image search linking back to an Argentine ebay-like site, but no evidence of the module still being up and for sale.


That last one might be enough in the resolution department for eagle-eyes, but I still can't make it out :/  

But if it was possible to find appropriate packages of the SGRAM to fit the more commonly-found DIMMs, is it even possible to turn a standard DIMM into the improved one? And if it is, then is it possible, or of any value, to bump the VRAM even higher? 

There’s so very nearly enough pixels to make out... but nothing I’ve shapeshifted it into has yielded a google result.

I tried compositing the two together, flanked by the originals to give my brain as much to work with as possible. Using a smartphone and holding it at different angles/zoom levels may help...


 

CM4132627143-10?

KMU3262Y1A3-10?

Wish I had the answer but maybe this image will click better for someone else. 

Unfortunately, no, nobody offered SGRAM in a package compatible with those EDO DRAM modules, so simple chip-swapping isn't possible. Aside from the 4400 and various clones based on that logic board, I don't think anything else used that VRAM module. But I think this is also true of the VRAM DIMMs in the 7 and 8 series models: exclusive to Apple and long out of production.

One of our resident geniuses could probably build a VRAM board that plugs into the 4400's VRAM slot and accepts the later ATI SODIMM-style VRAM modules, but that's way beyond my ability.

But yeah, I venture most people simply installed a new video card rather than trying to upgrade the VRAM on these so they're kind of hard to get. I would probably only bother looking seriously if I had a PC Compatibility Card and was going to use the GIMO pass-through for simplicity. Is that what you're doing?

Franklinstein said:

Unfortunately, no, nobody offered SGRAM in a package compatible with those EDO DRAM modules, so simple chip-swapping isn't possible.

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Damn. I feared as much. Well I did find a 4MB module here for $40, which, is steep like you mentioned in another thread of mine on the 4400 I think  .

I wonder. I know that the Mach64 went up to about 8 MB according to the wikipedia page, and I'm guessing it wouldn't benefit really from more than that. The Rage II on the higher end might, but I wonder how large the market would be... Thinking of the other projects on here, more folks have an SE/30 and want to add a better cache adapter to it than there are people who have Macintosh Portables, and special SCSI2SD boards are made for those. So you'd imagine the ownership of Tanzania-based machines is lower than that even... as someone on the IRC mentioned, "seems like it'd be cheaper just to slap a Rage128 in there" and they're probably right :lol:  

But if there's ever any larger scale desire for a standard one of those ideas would be ripe, for sure.

Franklinstein said:

 I would probably only bother looking seriously if I had a PC Compatibility Card and was going to use the GIMO pass-through for simplicity. Is that what you're doing?

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While that is a problem for my 4400/7220 board (because every DA-15 to DB-15 adapter I've ever tried has never worked properly), the StarMax boards all have DB-15, which makes my multi-sync  flat panel displays work just fine. The biggest thing I came to discover is setting up a proper profile for what display you're using in the PC Setup control panel. I didn't think about this and was royally pissed when the left or top was completely cut-off on the DOS side, no matter what I did on the monitor itself. Even my 13" High Resolution AppleColor RGB blah blah this name is too long, fixed-640x480 DA-15 monitor had issues.

Edit:  Even though the Mach64 on the card itself has VRAM, it doesn't use system VRAM does it? there's a weird expansion type port on the card, but I don't know what it's for. Some folks on Vogons theorized it might be for an ISA expansion that was never developed, but IDK.

jessenator said:

Damn. I feared as much. Well I did find a 4MB module here for $40, which, is steep

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That's probably a bargain compared to original MSRP.

jessenator said:

I wonder. I know that the Mach64 went up to about 8 MB according to the wikipedia page, and I'm guessing it wouldn't benefit really from more than that. The Rage II on the higher end might, but I wonder how large the market would be...

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Several computers used the Tanzania/II based board, including some non-Mac PPC workstations, so I imagine someone could sell at least 100 adapters if they were built. If they were <$20/ea, I'd buy two, at least. The 4400-VRAM-slot-to-ATI-SODIMM adapter shouldn't be very expensive: you're basically just building a small board and sticking a SODIMM socket on it into which the end user will install an appropriate SGRAM SODIMM. The adapter board should be simple in theory: just run the appropriate lines from the slot pins to the new socket and you're done. I doubt you'd even need any additional resistors or capacitors or other discrete components since they should already be in place on either the logic board or on the SODIMM module. 

jessenator said:

Even though the Mach64 on the card itself has VRAM, it doesn't use system VRAM does it?

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I don't know which model PC Compat card you have, so I can't say exactly what you may be looking at, but all of them from the original Houdini to the last 12" card have dedicated video memory, usually in the form of EDO DRAM. The PCI models should have at least 1MB each, with a couple empty sockets for expansion to 2MB of EDO DRAM on the 12" model. 

Franklinstein said:

The PCI models should have at least 1MB each, with a couple empty sockets for expansion to 2MB of EDO DRAM on the 12" model. 

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Yeah, that's what mine are (PCI). I upgraded one of them (the P133) to the max 2 MB. So I'm guessing on the PC side it only uses what's on the card (I don't recall specific numbers, but at above 640x480 you couldn't get true-color) 

Franklinstein said:

The adapter board should be simple in theory:

Click to expand...

My knee-jerk vote would be for a 90* adapter, but looking at it again just now, the module is well past the height of the PCI mounting, so no worries about it being vertical/in-line I guess.

If anyone with the technical prowess is lurking, I'm happy to lend a DIMM and/or Tanzania logic board to the cause.

I know I’m resurrecting an ancient thread, but I’ve just been going down this rabbit hole myself!

From what I’ve got so far the VRAM slot is pretty much a straight connection to the ATI chip and there’s no need for any glue logic, but it uses sense resistors on “specific lines” to determine the type of RAM installed. I can’t find any publicly available documentation on the ATI Mach64 line to figure out what those lines are, so I’m trying to track down a Mach64 card with SGRAM or some clean photos of a DIMM that hopefully gives enough info.

So far the spam sites are winning, there’s very little signal left in the noise.

sitharus said:

I’m trying to track down a Mach64 card with SGRAM or some clean photos of a DIMM that hopefully gives enough info.

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Is this any help?

jeremywork said:

Is this any help?

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There's a few too many buried traces on that board to follow without actually probing with a multimeter unfortunately :/

Any Mach64 VT board should do though, PC ones are the same chip. I'm going to keep looking through the second hand market and hopefully will find one, though it's a limited market here in New Zealand.

sitharus said:

I know I’m resurrecting an ancient thread, but I’ve just been going down this rabbit hole myself!

From what I’ve got so far the VRAM slot is pretty much a straight connection to the ATI chip and there’s no need for any glue logic, but it uses sense resistors on “specific lines” to determine the type of RAM installed. I can’t find any publicly available documentation on the ATI Mach64 line to figure out what those lines are, so I’m trying to track down a Mach64 card with SGRAM or some clean photos of a DIMM that hopefully gives enough info.

So far the spam sites are winning, there’s very little signal left in the noise.

Click to expand...

Have you looked at the Tanzania schematics, now publicly available? A cursory glance doesn’t reveal any of those sense resistors you mention.

croissantking said:

Have you looked at the Tanzania schematics, now publicly available? A cursory glance doesn’t reveal any of those sense resistors you mention.

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They're how the ATI chipset detects the type of RAM installed. With no resistors it must be EDO VRAM as that's all I've seen so far, you have to add pullup resistors to the DIMM so it can recognise SDRAM or SGRAM,

This is from Apple's technical documentation on the PowerMac 4400, which has the slot pinout but nothing more:

The graphics controller recognizes the presence of pullup resistors on certain data bits on the DIMM to determine which type of memory is present. The video controller supports 1, 2, or 4 MB of RAM for video memory.

Note
No video performance advantage is gained with EDO video DIMMs larger than 2 MB. 4-MB video DIMMs built with SGRAM and SDRAM devices provide higher bandwidth performance

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So I'd need to see a board with those resistors to be able to make a 4MB board that works, or a copy of the ATI Mach64 VT2 technical docs.

From what I’ve found so far the Motorola Starmax 3000/240 shipped with the 4MB vram module. I’ve only found one photo of the motherboard online and it’s good enough to show 4 QFP chips on the module which is exactly what I’d expect, but it’s top down so I can’t see the module detail.

I’ll keep searching.

I have my 4 MB SGRAM DIMM for Tanzania back from the OP, let me know if any pictures of that would help.

treellama said:

I have my 4 MB SGRAM DIMM for Tanzania back from the OP, let me know if any pictures of that would help.

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Yes that would be perfect!

Not mine, but from the original post, maybe? It's been ...a while.

I've been interested in making one for quite a while, I have a pair of 4MB DIMM but they have chips on both sides which is not ideal for assembly. That white module would be more ideal, I did not had the energy to route one from scratch which is why it has not been done yet. I also lacked a test machine but I now have a StarMax. The module is well documented in the Apple 4400 documentation.

Just be sure not to use white solder mask--Ariston Technologies has it trademarked!

Good, I don't really like white soldermask except when the application justifies it. I wonder if they've been able to enforce that trademark!

sitharus said:

Yes that would be perfect!

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Here are some pictures from my phone. Let me know if you need even higher res

I guess I know what I’m doing this evening

Those photos look great, except for that I can’t make white ones now due to the trademark . Looks pretty straightforward though, so I’ll trace them out and hopefully fire up KiCad in a couple of days.