How to test 30pin SIMMs ? \ VOGONS

How to test 30pin SIMMs ?

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First post, by Dave Bursik

Posted on 2020-11-19, 16:17

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Hello,

I have theese 30pin SIMM modules ( each od them is 512kB - I hope ).
I tried to use them in 386 or 486 motherboards, but BIOS cannot read them. It is strange, because there is no problem with all my 1MB modules.
Any idea how or where to test them ?

Thanks,
David

Last edited by Dave Bursik on 2020-11-19, 16:25. Edited 2 times in total.

Reply 1 of 13, by debs3759

Posted on 2020-11-19, 16:20

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Are they double sided? That poses a problem for some motherboards.

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Reply 2 of 13, by Dave Bursik

Posted on 2020-11-19, 16:23

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No, they are not double sided.
My 1MB modules are 1 sided too - there is no problem.
David

Reply 3 of 13, by Horun

Posted on 2020-11-19, 16:43

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Most older 286 and 386 motherboards that have 30pin simm sockets will only work with 256k, 1Mb or 4Mb simms.
Good examples is the ASUS ISA-386C or FIC LEO 386's.
I have some 2Mb 30 pin that only work in a specific AST motherboard (and an older Apple Mac)
What motherboard are you trying to test them in ?

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Reply 4 of 13, by Dave Bursik

Posted on 2020-11-19, 16:56

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I tested them on:
M321
M396 VR1.1
Unichip UNI-386WB 387C REV1.0

Also I have HED-988 board, but unfortunately there is possible to use only SIPP modules 🙁

Reply 5 of 13, by Grzyb

Posted on 2020-11-19, 17:12

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They are 256 KB + parity.
Are you sure the bank is filled up?
Memory bank = 2 x SIMM30 for 386SX, 4 x SIMM30 for 386DX/486.

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Reply 6 of 13, by Robin4

Posted on 2020-11-19, 19:37

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You can test these with a memory tester.. Which arent easy to get these days..

I used them myself.

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Reply 7 of 13, by Dave Bursik

Posted on 2020-11-20, 16:21

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Grzyb wrote on 2020-11-19, 17:12:

They are 256 KB + parity.
Are you sure the bank is filled up?
Memory bank = 2 x SIMM30 for 386SX, 4 x SIMM30 for 386DX/486.

Each module has two 256kB chip and third one for a parity. So I assume the capacity of each module is 512kB.

David

Reply 8 of 13, by maxtherabbit

Posted on 2020-11-20, 16:23

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Dave Bursik wrote on 2020-11-20, 16:21:

Grzyb wrote on 2020-11-19, 17:12:

They are 256 KB + parity.
Are you sure the bank is filled up?
Memory bank = 2 x SIMM30 for 386SX, 4 x SIMM30 for 386DX/486.

Each module has two 256kB chip and third one for a parity. So I assume the capacity of each module is 512kB.

David

Each "256kb" chip is 256k x 4 bits. It takes two of them to make 256 kiloBYTES

Reply 9 of 13, by Dave Bursik

Posted on 2020-11-20, 16:29

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maxtherabbit wrote on 2020-11-20, 16:23:

Dave Bursik wrote on 2020-11-20, 16:21:

Grzyb wrote on 2020-11-19, 17:12:

They are 256 KB + parity.
Are you sure the bank is filled up?
Memory bank = 2 x SIMM30 for 386SX, 4 x SIMM30 for 386DX/486.

Each module has two 256kB chip and third one for a parity. So I assume the capacity of each module is 512kB.

David

Each "256kb" chip is 256k x 4 bits. It takes two of them to make 256 kiloBYTES

Are all of them 256k x 4bit? I think just two modules are 256k x 4bit..

Reply 10 of 13, by maxtherabbit

Posted on 2020-11-20, 16:36

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Yes. Punch in the IC part numbers into google and see for yourself

Reply 11 of 13, by zyga64

Posted on 2020-11-20, 17:44

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Third IC (for parity) is 1-bit wide, which results with 9-bit SIMM.

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Reply 12 of 13, by Caluser2000

Posted on 2020-11-20, 18:10

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The Dos memory testers such as the ones in Norton Utilities , checkit , Central Point PC tools and many others should be able to test them just fine if the motherboard supports them.

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Reply 13 of 13, by Dave Bursik

Posted on 2020-11-24, 08:54

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Hello,

thanks. I checked DRAM configuration for the M321 motherboard.

DRAM CONFIGURATION
Size Bank 0 Bank 1
1MB (4) 256K x 9 NONE
2MB (4) 256K x 9 (4) 256K x 9
4MB (4) 1M x 9 NONE
5MB (4) 256K x 9 (4) 1 M x 9
8MB (4) 1M x 9 (4) 1M x 9
16MB (4) 4M x 9 NONE
20MB (4) 4M x 9 (4) 1M x 9
32MB (4) 4M x 9 (4) 4M x 9

So I think my modules should work with motherboard ... ???
Each module is 256k x 4-bit +256k x 4-bit + 1-bit wide parity chip

David

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