a Macintosh Display Card

[LOOM]

I got hold of a Macintosh Display Card 8•24GC rev B ROM today.







Can anyone see on the chips how much vram this is?

 

[trag]

To determine the VRAM from looking at the card we need to know the part number of the memory chips and the number of them on the board. It's hard to make out the part numbers from the photos.

Can you read the part number off of the sixteen identical memory chips, and also off the VRAM SIMMs. check the back of the board to make certain there aren't more memory chips hiding there.

I'm not sure but from what little I can make out, it looks like 768KB of VRAM, with a little guessing serving where knowledge is unavailable.

 

[Anonymous Freak]

Those appear to be 256 KB SIMMs (eight 256 Kilobit chips each,) so the total additional RAM would only be 512 KB, for a board-total 2.5 MB.

 

[mac2geezer]

Did that card come with the two Simms or did you get them elsewhere? Those are 64 pin Simms, Apple part number 333-0167 (I think) and seem to be hard to find. Would love to get a couple for my 8-24GC (and no, the IIfx 64 pin Ram Simms do NOT work; I've tried).

 

[LOOM]

Yes, the SIMMs came with the card. You mean these 256 KB SIMMs are hard to find, or a GC board with any SIMMs at all?

The SIMMs are identical 64 pins, and the chips are marked "TMS44C256DJ" & "EDP 026J P" on one side, "TMS44C256DJ" & "EDP 026W 7" on the other.

The only other number I can see is '9035' & "ZA2982L" (very tiny) marked vertically on one side, and "BE3-0" on the other side on the end of the pcb.

Could well be 256 Kb, but can't they also be 2MB each as well? (256KB* 8) This states that the "Macintosh Display Card DRAM Expansion Kit" can add 2MB more, but 3rd party SIMMs can expand memory up to 8MB. Optimistic, I know :lol:

Acording to this ROM version identifier it have a rev B ROM (341-0266). 1989,90.

 

[Anonymous Freak]

Sizes on individual chips are almost always in bits, not bytes. So 256 Kilobits. Eight of them (one full SIMM) would make 256 Kilobytes. Even today, the number on modern DDR3 chips is in Gigabits, so you have to divide by 8 to get Gigabytes per chip, then multiply by number of chips to see capacity of the entire DIMM.

 

[mcdermd]

It took me a while to figure that out. If someone had explained it to me as clearly as you did there, I would have gotten it right away.

 

[beachycove]

That is a coveted card, and the vram chips make it even more desirable. Well done.

Ideal for a IIfx or a Nubus Mac such as a IIci running System 6/ very early System 7.