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28-Pin SRAM

Agent Orange

Agent Orange

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Joined
Sep 24, 2008
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SE MI
My Gigabyte GA-486SF Project:

I need info (part numbers) for 28-pin 32KB SRAM for my GA-486SF mobo. The
board has 16 x 8 (256 KB) installed and I want to go to 512KB. The identifiers of the installed DIPS are as follows:
UM612256AK-15
94355
N70817

Any leads would be most appreciated.
 
Standard JEDEC pinout for a 62256 SRAM chip.

They are high speed 15ns SRAM used as Cache RAM on the motherboard.

I have them in stock but not listed on my website.

RJ
 
You can't upgrade to 512kb unless you have 16 sockets available. Because of the addressing limits of 28-pin SRAM, 32kx8 is the best you can do. There do exist 64kx8 and 128kx8 SRAMs in 32pin DIP package however. The 64kx8 parts were commonly found on 430FX motherboards. The 128kx8 chips are pretty hard to get though.

Not to disappoint you or anything, but it is very unlikely you will receive a significant performance boost with the upgrade you are attempting. I recently upgraded my 486 from 256kb to 1024kb cache.
 
Anonymous Coward said:
You can't upgrade to 512kb unless you have 16 sockets available. Because of the addressing limits of 28-pin SRAM, 32kx8 is the best you can do. There do exist 64kx8 and 128kx8 SRAMs in 32pin DIP package however. The 64kx8 parts were commonly found on 430FX motherboards. The 128kx8 chips are pretty hard to get though.

Not to disappoint you or anything, but it is very unlikely you will receive a significant performance boost with the upgrade you are attempting. I recently upgraded my 486 from 256kb to 1024kb cache.
Click to expand...
According to the GA-486VF manual you can. The jumper setting are available on the board. I realize that the benifits will be small, but this is a project to see how much I can sqeeze out of it.
 
Anonymous Coward said:
http://motherboards.mbarron.net/models/486vlb3/ga486vs.html

Go here and click on the photo to enlarge.
Click to expand...
Looks just like my board with the exception of 72-pin SIMMS, which would make that a GA-486VS.

I suppose I don't fully understamd your argument about the SRAM for this mobo. I thought it was a fairly straight forward upgrade, but apparently there is more to it then I had anticipated.

My real concern, however, is system memory. My mobo has 8 x 1 MB for a total of 8 MB. I ordered 16MB 16x9-70NS 30 Pin SIMM (8 sticks of 16MB) from DMS in New Hampshire and they don't work. They will being going back today. If you have a handle on 30 pin SIMMS that will work, please let me know. My goal is to get this mobo up to WIN98 specs; i.e., 24 MB minimum.

Thanx for the responses.

Agent Orange
 
I guess the point I am trying to make is that if your board only has eight or nine 28-pin SRAM sockets, then 256kb cache is as far as you can go. There is a physical limitation with this kind of package, as there aren't enough address lines to support higher memory densities. This is the reason why the 32-pin SRAM modules exist.

Here's a photo of your motherboard:

http://vogons.zetafleet.com/viewtopic.php?t=20867&sid=c292854e7ea443653da35dacc5328aaa

Like you said, it's the same thing with 30pin RAM sockets. (Note this board also accepts 32pin SRAM modules)

How much did you pay for those 16MB SIMMs? I'm interested in getting more if the price is right. They're pretty nice, but they don't work in all 486 motherboards. According to your motherboard manual, they should be supported. Perhaps you have an older revision in which does not support them.
 
Last edited:
Anonymous Coward said:
I guess the point I am trying to make is that if your board only has eight or nine 28-pin SRAM sockets, then 256kb cache is as far as you can go. There is a physical limitation with this kind of package, as there aren't enough address lines to support higher memory densities. This is the reason why the 32-pin SRAM modules exist.

Here's a photo of your motherboard:

http://vogons.zetafleet.com/viewtopic.php?t=20867&sid=c292854e7ea443653da35dacc5328aaa

Like you said, it's the same thing with 30pin RAM sockets. (Note this board also accepts 32pin SRAM modules)

How much did you pay for those 16MB SIMMs? I'm interested in getting more if the price is right. They're pretty nice, but they don't work in all 486 motherboards. According to your motherboard manual, they should be supported. Perhaps you have an older revision in which does not support them.
Click to expand...

Concerning the SRAM - both the mobo silk screen and the manual indicate that you can go 512 KB as follows: Tag SRAM=15 NS & Data SRAM=20 NS

Data SRAM = 512 KB
Tag RAM = 128 KBx8
SRAM SIZE = 32 KBx8
IC U No. = U1,U2,U3,U4
JP1-JP2-JP3-JP4 = (ON)-(ON)-(ON)-(1-2)

The 30 pin modules has 9 chips (parity) and are about twice the height of OEM chips. They failed to light up. I paid $8.00 a piece and $7.00 shipping
 
You spent a pretty penny on those SIMMs eh? I think that's about what I paid for mine 5 years ago. It's kind of a lot to pay for 128mb, but it is pretty nifty at the same time.

I think your motherboard manual might have an error. For 512kb cache, it should read:

Tag RAM = 32 KBx8
SRAM SIZE = 128 KBx8

The reason is that four 32kx8 SRAMs only adds up to 128kb, whereas four 128kx8 SRAMs total 512kb.
 
Anonymous Coward said:
You spent a pretty penny on those SIMMs eh? I think that's about what I paid for mine 5 years ago. It's kind of a lot to pay for 128mb, but it is pretty nifty at the same time.

I think your motherboard manual might have an error. For 512kb cache, it should read:

Tag RAM = 32 KBx8
SRAM SIZE = 128 KBx8

The reason is that four 32kx8 SRAMs only adds up to 128kb, whereas four 128kx8 SRAMs total 512kb.
Click to expand...

You are correct - I did a cut and paste and things didn't line up so good. I'd gladly pay 8 bucks a piece if the stuff works. Do you have a handle on what I need?
 
Can you post a clear close-up pic of the cache RAM in their sockets and a bigger pic showing the # of sockets and chips total?

I have a wide variety of cache RAM, we just need to figure out what you have and what you need.

RJ
 
channelmaniac said:
Can you post a clear close-up pic of the cache RAM in their sockets and a bigger pic showing the # of sockets and chips total?

I have a wide variety of cache RAM, we just need to figure out what you have and what you need.

RJ
Click to expand...

I will work on that today.
 
SRAM Pictures

SRAM Pictures

Sorry about that - another senior moment, I suppose. Football got in the way last weekend. I'll work on that tonight for sure tonight.
 
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