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Help finding faster alternative to IBM025171LG5B-70, VRAM 256kx16, SSOG-64

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First post, by feipoa

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Anyone know of a 60 ns or faster alternative to IBM025171LG5B-70, which is a VRAM chip of 256kx16 and footprint 0.472" SSOG-64? It would be for the MPEG-1 decoder card on my VLB S3 968 card.

I see in some online searches that there may be a 60 ns variant of IBM025171LG5B, but in asking some IC suppliers, they have none.

There is a datasheet here, http://www.datasheetcafe.com/ibm025160-datasheet-pdf/ , click the PDF at the bottom of the page. It doesn't mention the *B model, rather mentions the *D model, e.g. IBM025171LG5D. For the *D model, there are 60 ns and a faster 60 ns option (-6H). Are the *D variants compatible with the *B variants? Are there other brand alternatives to IBM025171LG5B ?

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Reply 1 of 5, by Thermalwrong

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Good job finding the datasheet - there's really little to find for that part code? I did find some related parts though. You can try searching for the IBM part code, the part code for the -60 is "26H1956", haven't found the 6H yet.

Are the *D variants compatible with the *B variants?

Probably? My understanding is that the B / D difference is just revision, I don't see any mention of automotive so it looks likely to be later revisions of the same part. I've been reading a lot of memory datasheets lately.

Check out the ATI PCI MACH64 cards, they seem to use a mix of that IBM chip and a TI part:

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That's TMS55166DGH for the EDO version like your 25171 part: https://www.alldatasheet.com/datasheet-pdf/pd … I/TMS55165.html
I'm not completely sure the pinout is the same, but that could be a difference in terminology between IBM and other companies.

Reply 2 of 5, by snufkin

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Looks like the datasheet was updated on 04/95 with "Major revision to update to Die Revision D preliminary specifications." Earliest datasheet I've found is 11/95, so still just with the D revision. I'd be surprised if different revisions weren't backwards compatible. I did also find an OKI sheet which claims to have matching parts: https://www.tvsat.com.pl/pdf/m/memory_oki.pdf
That has the OKI MSM5416283 and the NEC μPD482445 as matching parts.
MSM5416283 datasheet says it came in -70, -60 and -50nS parts.

Reply 3 of 5, by feipoa

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Thanks a lot everyone.

For the TI part, EDO VRAM, it has an option for 4-column block write capability (55166) and 8-column block write capability (55176). The IBM manual mentions 8-column, so either IBM 025170 is 4-column or 4-column and 8-column can be mixed.

Nonetheless, according to that compatibility sheet, the IBM 025171 is 8-column EDO VRAM, thus the equivalent TI part would be TMS55176-60DGH.

The OKI product doesn't specically mention EDO in the datasheet, but rather "Extended page mode". Is this the same as Extended Data Output (EDO)?

The non-IBM products use SSOP-64 rather than SSOG-64. These pretty much the same?

Summary, thus far, of replacements for IBM025171LG5B-70:

IBM025171LG5B-60
IBM025171LG5D-60
IBM025171LG5B-6H
TI TMS55176-60DGH or might be printed as TMS55176DGH-60
OKI MSM5416283-50 or might be printed as OKI MSM5416283-50GS-K
OKI MSM5416283-60 or might be printed as OKI MSM5416283-60GS-K
NEC uPD482445GW-60

Many thanks all.

Plan your life wisely, you'll be dead before you know it.

Reply 4 of 5, by snufkin

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feipoa wrote on 2021-12-31, 13:35:

The OKI product doesn't specically mention EDO in the datasheet, but rather "Extended page mode". Is this the same as Extended Data Output (EDO)?

It mentions it in passing on page 31, RAM Port Operation:

The MSM5416283 offers an accelerated page mode cycle (EXTENDED PAGE MODE) by eliminating output disable from CAS "high", and it allows CAS precharge time (tCP) to occur without the output data becoming invalid. This new data out operates (Extended data out) as any RAM read or Page Mode Read, except data will be held valid afterCAS goes "high", as long as RAS is "low".

But I don't know enough to say if that means it is directly the same.

feipoa wrote on 2021-12-31, 13:35:

The non-IBM products use SSOP-64 rather than SSOG-64. These pretty much the same?

I think SOP and SOG are interchangeable. Can't see any major size differences from the datasheets, and a JEDEC dictionary listed them in the same entry. Important dimension of 0.8mm between pin centers is the same. The total width (pin to opposite pin) is slightly different, with the IBM SSOG giving 14.0-14.5mm (with a .48-.68mm landing length) and the OKI SSOP giving 13.8-14.4 (with .55-.85mm landing length). So even if the OKI part is slightly short (13.8mm vs 14.0mm), the legs will still be over the PCB pads.

Reply 5 of 5, by feipoa

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I've received some quotes for the replacement chips. Prices aren't ideal by any means. I might try the NEC part.

IBM025171LG5B-70, SSOG-64, $8.8

IBM025171LG5B-60, SSOG-64, don't have

IBM025171LG5D-60, SSOG-64, $17

IBM025171LG5D-6H, SSOG-64, don't have

TI TMS55176-60DGH or TMS55176DGH-60 x10, don't have

OKI MSM5416283-50 or MSM5416283-50GS-K $5, but not original

OKI MSM5416283-60 or MSM5416283-60GS-K, $11

NEC uPD482445GW-60, $3.5

Does anyone have a preferred supplier in Asia for these hard to find obsolete IC's?

Plan your life wisely, you'll be dead before you know it.

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