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Macintosh IIvx, Detailed Scan/Image?

trag

Well-known member
I am looking for a detailed (good enough to read chip markings) image of a Mac IIvx motherboard.   Images of the P600 and IIvi will not do, as it is precisely the differences, I want to see.

Specifically, I'm interested in the corner/edge of the board where the Cache and Tag RAM chips are located, and possibly the underside of the same region.   I would like to know what parts Apple used for the cache SRAM and Tag SRAM.  Also, there are a number of empty resistor positions in the region on the Performa 600, that I suspect are populated on the IIvx.

The Tag RAM will be the difficult component to locate, but there's a seller on Ebay who has tubes of 30 chips which are probably the proper Tag for sale.  But I'm not sure.  I'd rather confirm it before I spend the money.

 

trag

Well-known member
Excellent, gpbonneau, thank you!   On magnified view I can make out the tag RAMs and they are ATT7C17, which is exactly what is available on Ebay at the moment.  The SRAMs are less critical as the pinout for those is a JEDEC standard, so any fast enough 8K X 8 SRAM in the 28 pin SOJ package should work.

I couldn't remember when I posted, but it turns out the resistors I'm curious about are on the back of the board.   Anyone have a detailed scan/photo of the back of a IIvx, specifically of the region which is the lower left hand corner in gpbonneau's photos?

 

trag

Well-known member
Thank you again, gpbonneau!   IIRC R125 and R124 are unpopulated on the P600.  So if I add the SRAM chips needed for the cache, I'll need to populate those resistor positions as well.   There might have been a couple of others, but I can use that photo to identify them.

 

trag

Well-known member
Interested to see the end results!


Looks like there won't be any.  At least not for a while, absent luck.  The four lots of 30 chips of the TAG SRAM sold before I got back to them today.   I would not have expected there to be much demand for them.    Ah, well.   Making a P600 slightly better is fun, but not Earth shattering.

 

Bolle

Well-known member
Some Cache DIMMs for the Nubus PowerMacs used chips that will do the job. The TAGRAM as well as the SRAM will fit.

 

trag

Well-known member
Thanks, Bolle.  That's good to know.   Looking at how difficult it can be to find old TAG RAMs, I wish I had bought one of those lots of 500 L2 caches from OWC, back when.  I forget what they were asking -- something like $125, or $.25 each, IIRC.   I could never think of a reason why the expense was worth it at the time.

 

trag

Well-known member
Interesting to note that in one of the photos that gpbonneau provided the data cache chips are 15ns and in the other photo of the other board they are 20ns. I hope that means that 20ns is fine, and they just used faster on some boards -- as opposed to 15ns is really needed and they found some chips marked 20ns that operated fine at 15ns.

 

Fizzbinn

Well-known member
Interesting to note that in one of the photos that gpbonneau provided the data cache chips are 15ns and in the other photo of the other board they are 20ns. I hope that means that 20ns is fine, and they just used faster on some boards -- as opposed to 15ns is really needed and they found some chips marked 20ns that operated fine at 15ns.
20ns on mine:

29B3B960-2D23-4D24-B51D-5757151E8F17.jpeg

F8CD9BA8-9F2E-4573-B719-326C13755EEB.jpeg
 

trag

Well-known member
@Fizzbinn Thank you. I hope that means that 20ns will work. I'm not in much danger of getting to this project soon, too many other immediate things going right now. But I have some of the TAG SRAMs on hand. And I have a bunch of 20ns 32KB X 8 SRAMs.

IIRC, the JEDEC pinout for the 32KB SRAM is the same as for the 8KB SRAM, but with a couple NC pins converted to address lines.

The main issue with the chips I have on hand is that they are 20ns.

Yes, I'll be "wasting" 3/4 of their capacity, but I have several hundred of them, whereas I'd have to hunt down and purchase 8K X 8 chips.
 
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