Here is a very good thread that has the answers to your issue: 440BX - BIOS shows 756MB and CPU-Z shows 1 GB: Which is right?

I think that thread would be great if OP had order of magnitude more ram. As is it might be broken components on the board, missing connection to one of address lines limiting size or maybe even chipset balls.

Hi there, take out cpu from slot and check if all cpu pins are straight/not missing

Just in case you haven't already found it, here is a link to the manual for the Shuttle HOT-685:
https://theretroweb.com/motherboard/manual/68 … 70182024617.pdf

Page 18 states that you can install DIMM's in any or all of the 3 DIMM slots, so at least which slot you use should not be an issues as long as you're using compatible DIMM's (and the slot is not damaged).

Did you check the OS selection option in the BIOS? Perhaps it's set incorrectly? I ask because it mentions a 64MB limit.

FYI, I forgot to mention that the information in the previous post regarding the "OS Select For DRAM > 64MB" option comes from pages 26 and 28 of the manual.

mx597 wrote on 2024-10-02, 00:57:

"OS Select For DRAM > 64MB"

that option only influences BIOS INT 15h/88h response, doesnt do anything to ram detection
https://www.os2museum.com/wp/windows-nt-3-1-a … mory-detection/

> infamous “OS select for DRAM > 64MB” option found in many BIOSes, with the choices being “OS/2” and “Non-OS/2”. The option is only useful for OS/2 2.11 and early OS/2 Warp FixPack levels, not for OS/2 in general. On systems with more than 64 MB, it reduces the memory reported via INT 15h/88h to exactly 15 MB, so that the amount of extended memory below 16 MB reported by INT 15h/E801h matches. That satisfies the assumptions of OS/2 2.11/Warp, and presumably NT 3.1, allowing the OS to recognize more than 64 MB RAM.

rasz_pl wrote on 2024-10-02, 00:13:

I think that thread would be great if OP had order of magnitude more ram. As is it might be broken components on the board, missing connection to one of address lines limiting size or maybe even chipset balls.

I'm going with this.
Check the tiny components around the ram slots.
Resistors should not be open circuit, caps should not be short.

The most common issue I encountered with 440BX boards back in the day was people using memory that was too new. Fewer chips on the ram stick = higher density memory and it's no surprise you're seeing only 64MB on 128MB stick.

I bet if you put a 128MB stick in there with 8 chips on 1 side it'll be fine and that board should be just fine with 3x256MB low density sticks (16 chips).

How many memory chips are actually on the stick you're trying to put in? Post a pic if possible too.

Interesting that so many soc 370 issues showing up lately... just an observation.

rasz_pl wrote on 2024-10-02, 02:41:

that option only influences BIOS INT 15h/88h response, doesnt do anything to ram detection https://www.os2museum.com/wp/windows- […]
Show full quote

mx597 wrote on 2024-10-02, 00:57:

"OS Select For DRAM > 64MB"

that option only influences BIOS INT 15h/88h response, doesnt do anything to ram detection
https://www.os2museum.com/wp/windows-nt-3-1-a … mory-detection/

> infamous “OS select for DRAM > 64MB” option found in many BIOSes, with the choices being “OS/2” and “Non-OS/2”. The option is only useful for OS/2 2.11 and early OS/2 Warp FixPack levels, not for OS/2 in general. On systems with more than 64 MB, it reduces the memory reported via INT 15h/88h to exactly 15 MB, so that the amount of extended memory below 16 MB reported by INT 15h/E801h matches. That satisfies the assumptions of OS/2 2.11/Warp, and presumably NT 3.1, allowing the OS to recognize more than 64 MB RAM.

Thanks for explaining what that option is about... I had long since forgotten the details but thought it was worth mentioning since it's easy to try and OP's board is seeing only 64MB.

andreipasca wrote on 2024-10-01, 21:06:

Hello guys,
I have a Shuttle HOT-685 motherboard, and no matter how I out the ram sticks, or in which slot it sees only 64mb. I even tried a 128mb stick, and it still shows as 64mb (also tried 2x64 and 128+64mb sticks) also I noticed that whenever I fill all three slots, it starts but displays nothing. Any ideas? I'm desperate.

Can you tell us more about the provenance of the parts? For example, did the motherboard come with the DIMM modules you are testing it with? If so, do you know if this combination ever worked together before? If this is the case it would point to a "new" hardware problem that developed at some point (bent pin, bad cap, etc.)

If the motherboard and the DIMM modules come from separate sources and have never worked together before, it's more likely to be a compatibility/speed issue (like pete8475 pointed out).

mx597 wrote on 2024-10-02, 05:45:

[...]

Can you tell us more about the provenance of the parts? For example, did the motherboard come with the DIMM modules you are testing it with? If so, do you know if this combination ever worked together before? If this is the case it would point to a "new" hardware problem that developed at some point (bent pin, bad cap, etc.)

It would also be good to know what chips are on the DIMMs (the first line of numbers on a chip IC is generally the model number) and number of those chips per DIMM - and if there is any difference between behaviour depending on which slot a DIMM is inserted into.

If the motherboard and the DIMM modules come from separate sources and have never worked together before, it's more likely to be a compatibility/speed issue (like pete8475 pointed out).

Possibly, but given the numbers I'm not so sure. i440BX can handle chips up to 128Mb, so for a 128MB DIMM to get recognized as 64MB, it would have to have four 256Mb chips, probably 16Mx16. That's theoretically possible but it would make it a very unusual DIMM. I'd say particularly given the complete failure to boot with 3 DIMMs installed regardless of order, some physical damage to the board matches the description better.