You'll need 4 or 8 of 30 pin simma. Most likely the mobo bios/chipset only sees/supports 16megs all up.

Caluser2000 wrote on 2020-12-29, 04:38:

You'll need 4 or 8 of 30 pin simma. Most likely the mobo bios/chipset only sees/supports 16megs all up.

It’s a 386sx so it only has a 16 bit memory bus, which is why it works with 2 simms.

Have ran CheckIt! on all the simms?

If your board doesn't support 4MB SIMMs, there's not much you can do except get an ISA RAM card, though of course it will be slower than onboard RAM, it's still better than no upgrade at all.

douglar wrote on 2020-12-29, 04:28:

Does anyone know if any Ali M1209 boards supported 4MB simms?

Is there any way to find out by poking around in the BIOS dump?

Yes, there is a way. The BIOS auto-detects the SIMM configuration and configures the chipset accordingly. 3 banks of 1MB SIMMs is unsupported, and causes fallback to 1M. Your best way of action is obtaining a working 8th 1MB module. The following configurations are supported:

1 B0  B1  B2  B3
2256  -   -   -  -> 512K (Code 1)
3256 256  -   -  ->   1M (Code 2)
4256 256 256 256 ->   2M (Code 3)
5 1M  -   -   -  ->   2M (Code 5)
6256 256  1M  -  ->   3M (Code 8)
7 1M  1M  -   -  ->   4M (Code 6)
8 1M  1M 256 256 ->   5M (Code 4)
9256 256  1M  1M ->   5M (Code 0)
10 1M  1M  1M  1M ->   8M (Code 7)

Technical detail: The code number for the RAM configuration is stored in the top four bits of chipset configuration register 10h, the total amount of on-board memory in Megabytes (1 in case of 0.5MB) is stored in the top four bits of chipset configuration register 12h. Chipset configuration is accessed using indexed port I/O at 22h/23h.

From what I can see, the other two boards with a M1209 chipset only support 1MB per module, so yeah, 8MB might be the max memory config you can do.

http://www.win3x.org/uh19/motherboard/result/?chipsetId=745

Thanks for the help.

ISA Ram? Wow. Interesting idea. Didn't think about that. I'd worry that the ISA ram is likely not L2 cacheable, except this this little board doesn't even had an L2 cache, so no worries, right?

As much fun as it would be to try to get this little fellow running with something like that, I don't love it so much that I want to invest that kind of money in esoteric equipment just to get there.

Right now, I'm not even particularly motivated to spend money to replace the bad simm that's limiting me to 4MB RAM right now. I'd probably find one at a thrift store before this board finished installing Win95 as it is, 🤣!

It could be the slowest 386 I've worked with. It manages to score over 31,000 realtics in Doom with an ISA Stealth 64 .

douglar wrote on 2020-12-29, 17:52:

ISA Ram? Wow. Interesting idea. Didn't think about that. I'd worry that the ISA ram is likely not L2 cacheable, except this this little board doesn't even had an L2 cache, so no worries, right?

ISA RAM boards can run at zero wait states, which means it takes two ISA clocks (at 8MHz) for a single 16 bit access. Onboard RAM also can support 0WS cycles (and often does for page hits in fast page mode RAM), which means an onboard RAM cycle takes two processor clocks (at 16/20/25 MHz), so onboard RAM can definitely be faster than RAM on ISA RAM expansion cards. I still remember the time where the whole world seemed swamped in 30-pin 1MB SIMMs no one needed anymore, so it's a strange feeling for me to see these modules today at prices that are way above shipping costs. One should be able to catch some cheap modules with a bit of patience, even the (likely slightly rarer) 9-chip modules.

mkarcher wrote on 2020-12-29, 18:45:

I still remember the time where the whole world seemed swamped in 30-pin 1MB SIMMs no one needed anymore, so it's a strange feeling for me to see these modules today at prices that are way above shipping costs. One should be able to catch some cheap modules with a bit of patience, even the (likely slightly rarer) 9-chip modules.

Very true. The days of getting a mixed bag of 50 simms for $10 seems to have passed.

In the US right now, used 1MB 9-chip simms are selling $6-$10 each, depending on what speed you want. That's within 10% of the price as newly made 4MB 9-chip 60ns simms. I bought a set of the 4x 4MB simms , which are probably more valuable than the mobo. And then this ungrateful little board didn't seem to care for them. So now the board gets sent to bed with 4MB of ram and it can be ram starved all night for all I care. I got plenty of other memory hungry boards that would gobble up those 4MB sticks for dinner! 😁😁

I think I spent 2 hours trying to find an arrangement where 3 chip simms or the bad 9 chip simm would pass test 3 in Memtest+. Had to explain to my kids what I meant when I kept muttering "Come on!! No Whammies!!".

I've got a few 30 pin SIMMs. If they fail CheckIt! out to the trash they go....

Caluser2000 wrote on 2020-12-29, 20:24:

I've got a few 30 pin SIMMs. If they fail CheckIt! out to the trash they go....

Nice collection, and I wanted to look at the simms, but like the camera, all I could do was focus on the sock!!

I prefer memtest+ to CheckIt, but yeah, I agree, bad ram has to go and I tossed the bad simm in the trash once I isolated it, but once I realized I couldn't get any of the known good 3chip simms to work for any length of time, I thought there might be a chance that if I just put the simms in a different order, maybe they could along with Ali M1209 in some weird quirk of fate, so I pulled it back out of the trash and peeled off the wad of tape that read "BAD" that I had stuck on it. But no, they didn't get along and back in the trash it went.

The ISA bus can only address (the lower) 16MB of memory. Would be a bit pointless to make an ISA expansion card that supports 4MB sticks

maxtherabbit wrote on 2020-12-29, 22:19:

The ISA bus can only address (the lower) 16MB of memory. Would be a bit pointless to make an ISA expansion card that supports 4MB sticks

The ISA bus is 16 bits wide, so 2 sticks form a bank. 2*4MB = 8MB on an ISA memory card might make sense.

mkarcher wrote on 2020-12-29, 22:24:

maxtherabbit wrote on 2020-12-29, 22:19:

The ISA bus can only address (the lower) 16MB of memory. Would be a bit pointless to make an ISA expansion card that supports 4MB sticks

The ISA bus is 16 bits wide, so 2 sticks form a bank. 2*4MB = 8MB on an ISA memory card might make sense.

I suppose you're right looking at it from a modern perspective that would indeed work fine, but I'm fairly sure such a thing was never built back in the day

Here's one that take 4MB simms: https://arvutimuuseum.ee/th99/i/A-B/52462.htm

I imagine if there was a board that switched between EMS and XMS, maybe you would put more than 16MB on it, but I never saw such a thing.

douglar wrote on 2020-12-29, 23:48:

Here's one that take 4MB simms: https://arvutimuuseum.ee/th99/i/A-B/52462.htm

I imagine if there was a board that switched between EMS and XMS, maybe you would put more than 16MB on it, but I never saw such a thing.

Well I stand corrected!

Here's one that says 32MB -- But I don't have enough documentation to figure out if that's EMS only.

https://arvutimuuseum.ee/th99/i/I-L/50517.htm

The Acculogic Rampat! and Rampat! Plus are both EMS only cards.

douglar wrote on 2020-12-30, 00:07:

Here's one that says 32MB -- But I don't have enough documentation to figure out if that's EMS only.
https://arvutimuuseum.ee/th99/i/I-L/50517.htm

I think that is also an EMS only card from what found googling.

32MB cards for ISA definitely exist. I have one called Orchid Ramquest 8/16. It can be used as conventional backfill, LIM 4.0 EMS or XMS, but obviously the memory beyond 24-bit addressing can only be configured for EMS. Never tried it in a 386, though it should work.