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PS/2 model 70 386 Memory Issues

NeXT

NeXT

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I'm trying to build an 8570-A16 machine and max it out with 16mb ram. Should be fairly easy as I'm swimming in 4mb SIMMs with IBM branding. Machine reportedly needs 80ns parity ram.

Problem is that when it's not giving a 2xx error (mainly 211, 216 and 225) with whatever memory I choose it's only declaring each stick to be 1mb.

EG: I have two sticks loaded with eight HM514400BS7 4mbit DRAM chips. Rates 70ns. Pop one in and all it sees is 1mb. Pop both in and now it's 2mb.

I also got other sticks with similar 14400 markings on their chips (A14B00J2x, TP104400J2C etc.) and they all also read just 1mb. I don't get it.
 
Well it seems to be old enough. I know that the really early PS/2 72 pin ram is special stuff so I'm assuming I'm on the right track if it's POSTing with it.

IMG_1196.jpg


I tried verifying the size of the sticks on a newer 56 SLC2 and an even newer P1 machine and both of them HATED the stuff. Wouldn't even POST.
 
NeXT said:
...so I'm assuming I'm on the right track if it's POSTing with it.
Click to expand...
Sounds like a bad assumption. It's posting with it because it recognizes 1 MB per stick and that runs the machine. It's not the right stuff because it *only* recognizes 1 MB per stick instead of four. I've seen similar scenarios on non PS/2s where the ram didn't get fully recognized.
 
I've never run into a situation like that. Either the machine added it to the count or denied it ever existed.

Anyone else here might be a bit more able to explain what might be up?
 
Okay then, so given how the 8570 isn't at all an uncommon machine does anyone know what memory this machine DOES support?
 
IBM has several different motherboards for the Model 70. Type 1 and 2 motherboards have 3 memory slots which can take either 1MB or 2MB SIMMS for a maximum of 6 MB. Type 3 and 4 motherboards have 4 memory slots which can only take 2 MB SIMMs for a total of 8MB. 4 MB SIMMs will not work according to IBM. 16MB is the system maximum but that requires installing an MCA card for extra memory.

See page 3-29 of the Hardware Interface Technical Reference. A PDF version of this document is available http://www.mcamafia.de/pdf/pdfref.htm
 
krebizfan said:
IBM has several different motherboards for the Model 70. Type 1 and 2 motherboards have 3 memory slots which can take either 1MB or 2MB SIMMS for a maximum of 6 MB. Type 3 and 4 motherboards have 4 memory slots which can only take 2 MB SIMMs for a total of 8MB. 4 MB SIMMs will not work according to IBM. 16MB is the system maximum but that requires installing an MCA card for extra memory.

See page 3-29 of the Hardware Interface Technical Reference. A PDF version of this document is available http://www.mcamafia.de/pdf/pdfref.htm
Click to expand...

I have the later A16 variant with the four slots and the CPU daughtercard. The statement that 2mb 80ns sticks are what I need according to the PDF conflicts with a note in the previous link.
The 2MB 80ns SIMM is for use on the 8570-A21 only.
Click to expand...
So...I give it my THM365120ASG-70's but fails both with 211 (Error in first 64KB of RAM. Later confirmed this with my standalone ram tester. :( ). Tried my 80 and 85ns stuff anyways and no surprise, 225 error.
Holy crap this machine is anal about what memory it wants. I fed it other low capacity 70ns sticks and it just wants none of this.
 
Last edited:
I had about 20 SIMMs marked IBM that I tried in a PS/57, PS/2 77 and PS/VPs: no luck! :)

Good luck!
 
NeXT said:
So...I give it my THM365120ASG-70's but fails both with 211 (Error in first 64KB of RAM. Later confirmed this with my standalone ram tester. :( ). Tried my 80 and 85ns stuff anyways and no surprise, 225 error.
Holy crap this machine is anal about what memory it wants. I fed it other low capacity 70ns sticks and it just wants none of this.
Click to expand...

Have you tried to clean the contacts of the SIMMs? They look kinda tarnished and crusty.

I've had piles of memory that has failed memory tests or caused the computer to not boot due to dirty contacts. Aluminum contact SIMMs usually don't get too crusty, but copper loves to get oxidized and corroded to the point where it interferes with signalling.

A pencil eraser is a quick fix, but it leaves scuffing that can tarnish 10x faster. A drop of that phosphor rust remover on a Q-tip works better and doesn't damage the contacts.
 
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