286 board identification / max. ram expansion \ VOGONS

286 board identification / max. ram expansion

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First post, by shock__

Posted on 2015-03-27, 17:12

shock__ Offline

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Rank: Oldbie
Posts: 1162
Joined: 2010-12-22, 01:53
Location: Berlin, Germany

Hey ...
I just finished rebuilding a formerly SIPP board to accept SIMM RAM.
Picture here ... sadly no markings on the board which would give usable results on google:
http://i.imgur.com/mvCYRuc.jpg

I've managed to expand the 1MB on board to 4MB using 4x 1MB sticks. Sadly I can't seem to get any memory available beyond the 4MB ... is there a chance I could use the memory inside the SIMM sockets along the memory onboard? 4MB sticks are rejected (board won't show anything) 🙁 I've interpreted the empty sockets near the on board RAM as ECC options (which might possibly be wrong).

There are 3 jumpers near the memory area (which is pretty much everything the board has when it comes to jumpers, apart from the usual suspects [reset, speaker, turbo, extbat, etc.] ... there's 1 additional jumper near the 8041 PPI, which does nothing as expected), this is the truth table I came up with:

With 4x 1MB sticks installed:

1J1 J2 J3 result
2 1  1  1 1MB
3 1  1  0 1MB
4 1  0  1 4MB
5 1  0  0 4MB
6 0  1  1 1MB
7 0  1  0 1MB
8 0  0  1 4MB
9 0  0  0 4MB

SIMMs not populated:

1J1 J2 J3 result
2 1  1  1 1MB
3 1  1  0 64kb
4 1  0  1 invalid
5 1  0  0 invalid
6 0  1  1 1MB
7 0  1  0 64kb
8 0  0  1 invalid
9 0  0  0 invalid

J2 seems to be related to the board accessing the SIMM banks, while J1 appears to be related to wait states as counting RAM takes a good bit longer with it set and seems to have no effect on the total amount of RAM in either scenario.

Any ideas?

Current Project: new GUS PnP compatible soundcard

[Z?]

Reply 1 of 3, by Caluser2000

Posted on 2015-03-28, 01:22

Caluser2000 Offline

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Posts: 3672
Joined: 2014-10-21, 05:34
Location: NOO ZEELUND

Do you have any references for your mobo for the max. amount of ram it can take? Some 286 mobos only supported 4megs total and some 8megs. If it can take 4 x 4meg sticks 30pin sticks the ones you have are most likely the incorrect type.

There's a glitch in the matrix.
A founding member of the 286 appreciation society.
Apparently 32-bit is dead and nobody likes P4s.
Of course, as always, I'm open to correction...😉

Reply 2 of 3, by Robin4

Posted on 2015-03-28, 04:28

Robin4 Offline

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Posts: 2435
Joined: 2011-04-04, 09:52
Location: The Netherlands

Why would you need more then 4MB on a 286 motherboard..

~ At least it can do black and white~

Reply 3 of 3, by Caluser2000

Posted on 2015-03-28, 04:31

Caluser2000 Offline

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Rank: l33t
Posts: 3672
Joined: 2014-10-21, 05:34
Location: NOO ZEELUND

That question is quite easy to answer- Because you can. I've 8megs on mine. Its a my one is bigger than your one thing you see- http://www.vintage-computer.com/vcforum/showt … odel-ZCV-251-EC

Ram for these systems now are a lot cheaper than what they use to be when these systems were new, so really there' s no reason not to max. the systems out if possible. Also a 286 in running Windows 3.1 in standard mode is quicker than a 386SX of the same clock speed in 386ehn mode don't ya know and the extra memory is handy.

Had the same question asked about my P200mmx with 256meg of ram and the same answer applies-because I can.. And the same applies to my 486 with it's 64 megs of ram.

There's a glitch in the matrix.
A founding member of the 286 appreciation society.
Apparently 32-bit is dead and nobody likes P4s.
Of course, as always, I'm open to correction...😉

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