Assuming you mean Amptron PM-8600, your board has a Via VP1 chipset from 1996 - only the second ever made to support SDRAM (after Intel's 430VX).

Back then you didn't have 128MB DIMMs. The VP1 has 12 address lines for RAM meaning it can address max 16 Mb per chip. A 128MB DIMM will have at least 64Mb chips (16 chips on the DIMM) but could also have 128Mb chips (8 chips on the DIMM) or even 256Mb chips (4 chips). With only 12 address lines available your motherboard will only be able to use the first 16Mb of every chip. If you are getting 32MB total that means it sounds like you have 16 chips (as 32MB = 16 x 16Mb).

This is a hard limit and indeed means you can't get more than 32MB per DIMM on boards using this chipset. Additionally, the 'floating' address lines on the chips not connected to the memory controller in this situation may cause issues - there's currently another active topic about a mod to the DIMMs to solve that. Assuming you don't want to solder resistors onto your 128MB DIMM to use it as 32 MB, you're probably best off going back to your 32MB SIMMs.

Note that you can install up to 128MB on the board using four 32MB SIMMs - but then you hit the next issue: unless you have 512kB of L2 cache (and with this PC Chips board you're lucky to have any and will not have more than 256kB), it can cache 64MB max. Adding more than that will slow down your system unless you're actually using more and the alternative would be thrashing to disk.

Bottom line: for a board from 1996 it's better to stick to an amount of RAM from 1996. Back then 16MB was normal, 24MB a lot and 32MB crazy. This board will go up to 64MB without issues which was more than good enough at the time.

Hello dionb,

thank you for such a complex answer. I will have to think about it many times. Until then I am going to make some reactions to each of your section:

1st - my mistake, yes, it is Amptron :-]. If you mean by VP1 Apollo VP VT82C585VP, then probably yes, haven't checked it yet.

2nd - this was little bit Spanish village for me, as we here in Slovakia use to say to things which are hard to understand, but I gave it a thought: that module has 8 chips, so according your info when each has 128Mb, then it is 128Mb x 8chips=1024Mb/8Mbit=128MB. When the chipset can address only 16Mb per chip, then it is 16MB. Understood. But when I inserted only that one module, it showed 32MB. After I put back those two simms with the dimm still in place, now the dimm added 16MB.

3rd - "This is a hard limit and indeed means you can't get more than 32MB per DIMM on boards using this chipset" - strange, because manual contains different info, but I am not arguing and you explained it already.
- no, I don't wanna solder anything :-]

4th - "Note that you can install up to 128MB on the board using four 32MB SIMMs" - clear. - the cache according manual should be 512kB.

Bottom line: thanks again for these usefull information. I will stick to those two simm modules plus one 16MB instead of the 128MB.

The soldering isn't terrible, I did a write-up here with pictures: Re: Can u pls help identify motherboard? Detects 64MB SDRAM as 16MB?