Interesting. Made a similar 'discovery' myself years back, that it wasn't just the i440LX and EX that worked with twice the density they officially supported, but the i430TX did so too (so you could use 2x 256MB = 512MB, even if you could only cache 64MB of it...).

That said, I've messed around with VX boards a lot and never seen anything like this. Sort of sorry I don't have one around now to see if I could reproduce it 😮

...and I was so happy to find a 2-slot VX to pair with those oddball 16-chip 32MiB modules...

But, they're still an officially good match. And I experienced problems with these VX-density modules and later chipsets anyway. My stockpile mostly consists of BX-friendly modules but kept "TX grade" (may be a 'misnomer' as you wrote i430TX may accept BX-grade densities - but it can't cache them so I'm better off with not going over 64MiB) and, as you can see, "VX grade" ones too, just to be prepared for anything.

And there are chipsets from other manufacturers, too, there may be many anomalies... I've even seen a 5ALI61 POSTing with a 1GiB module, detecting the whole size and even booting up with it (DOS only, sorry, so it was entirely pointless) - but I wouldn't trust this combo with my life. It's way outside of its cacheability limits too.

A VX supports 32 chip low density 64mb SDRAM

It’s not a discovery and right in the spec,
Sadly those are very rare so you almost always need to use a more common 256mb low density dimms at part capacity to make it work at partial density 64mb, it should be perfectly stable

EDO dimms are just easier to find in 64mb sizes that work on a VX than sdram dimms that are detected correctly @ 64mb

Tetrium wrote:

I wasn't expecting this, but it wouldn't be impossible for a "discovery" like this to be made (this forum is full of discoveries […]
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Kcil wrote:

Hi, just found a conflicting fact. I tried to install 2 sticks of 128MB SDRAM with 16 chips, and my computer POSTed with memory […]
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dionb wrote:

No downside to using a larger DIMM that is only partly being addressed. It's a "waste", but if it's easier to source the larger module, that's not really an issue.

As for caching, that only happens over the addressed area (it's one layer up, logically speaking), so only the memory actually detected counts. As far as an i430VX motherboard is concerned, that 128MB DIMM with 64Mb chips is a 32MB DIMM with 16Mb chips and so all those 32MB can be cached (as indeed could a second identical DIMM).

Hi, just found a conflicting fact. I tried to install 2 sticks of 128MB SDRAM with 16 chips, and my computer POSTed with memory test failure. I have isolated the problem that my board simply wont accept 2 sticks put together (I have placed each stick in each DIMM and in all cases, my computer will POST successfully).

Then I put in a 256MB SDRAM stick with 16 chips (if I calculate correctly that means each chip is a 128Mb chip) and the BIOS reported 64MB of RAM. Checked the integrity with Memtest and it passed 100% test. Wouldnt this mean 430VX can make do with 32Mb chip (16x 32Mb = 64MB, right?) So this contradicts with the info you said that VX can only see 16Mb per chip. Or is there a mechanism where physically the memory stick has 16 chips, but the system sees 32 chips instead?

I have quickly tested with another 430vx board and the result is the same (BIOS sees 64MB of RAM).

I wasn't expecting this, but it wouldn't be impossible for a "discovery" like this to be made (this forum is full of discoveries 😁).
For instance, 440LX was reported to work only with 128MB SDRAM modules, but it will work with 256MB SDRAM modules (both LX and BX have the same limitations though regarding certain higher density memory modules).

But it may be some odd thing to do with your memory module or it may be your BIOS misreporting or something else.

And even if it were to be legit, it won't guarantee the VX will run stably.

Could you post a couple pics of the memory module and the model numbers of your module and the VX motherboards you are using?

The mainboard is PCPartner MB520NH, and the memory stick is an old Visipro PC133 16-chip stick. Will post pics later, sorry for the delay I didnt have the chance to open vogons recently.

Here are some pics. Sorry I cant really dismantle the mainboard to have a clean look.

The memory stick is Visipro brand, with Samsung chips that say K4S280832C-TC75.

rmay635703 wrote:

A VX supports 32 chip low density 64mb SDRAM […]
Show full quote

A VX supports 32 chip low density 64mb SDRAM

It’s not a discovery and right in the spec,
Sadly those are very rare so you almost always need to use a more common 256mb low density dimms at part capacity to make it work at partial density 64mb, it should be perfectly stable

EDO dimms are just easier to find in 64mb sizes that work on a VX than sdram dimms that are detected correctly @ 64mb

It's kinda odd to see a consumer motherboard see support memory modules with 32 chips.
I think I have seen a DIMM like you mentioned once. It was not a registered module or anything. It was basically a standard usual SDRAM DIMM with a second set of rows of memory chips stacked above the 'usual' memory chips.
I also have SIMMs that look like this, but the motherboard I tried it in became unusably unstable which was fixed when I added in the standard 32MB SIMMs.

But this could very well explain what Kcil has observed.

Kcil wrote:

Here are some pics. Sorry I cant really dismantle the mainboard to have a clean look.
-snip-

The memory stick is Visipro brand, with Samsung chips that say K4S280832C-TC75.

Are you using a modded BIOS perhaps?

Tetrium wrote:

It's kinda odd to see a consumer motherboard see support memory modules with 32 chips. I think I have seen a DIMM like you menti […]
Show full quote

rmay635703 wrote:

A VX supports 32 chip low density 64mb SDRAM […]
Show full quote

A VX supports 32 chip low density 64mb SDRAM

It’s not a discovery and right in the spec,
Sadly those are very rare so you almost always need to use a more common 256mb low density dimms at part capacity to make it work at partial density 64mb, it should be perfectly stable

EDO dimms are just easier to find in 64mb sizes that work on a VX than sdram dimms that are detected correctly @ 64mb

It's kinda odd to see a consumer motherboard see support memory modules with 32 chips.
I think I have seen a DIMM like you mentioned once. It was not a registered module or anything. It was basically a standard usual SDRAM DIMM with a second set of rows of memory chips stacked above the 'usual' memory chips.
I also have SIMMs that look like this, but the motherboard I tried it in became unusably unstable which was fixed when I added in the standard 32MB SIMMs.

But this could very well explain what Kcil has observed.

Kcil wrote:

Here are some pics. Sorry I cant really dismantle the mainboard to have a clean look.
-snip-

The memory stick is Visipro brand, with Samsung chips that say K4S280832C-TC75.

Are you using a modded BIOS perhaps?

The board is using a modded BIOS to recognize >8GB HDD (https://www.wimsbios.com/biosupdates/large-hd … t/pcpartner/236). But apart from that specific feature, I am not aware of any mod being put into the BIOS image.

On stability note, I can only say I haven't encountered any unexplained crash, with DOS and Win95C easily running for hours.

rmay635703 wrote on 2019-04-19, 06:35:

A VX supports 32 chip low density 64mb SDRAM […]
Show full quote

A VX supports 32 chip low density 64mb SDRAM

It’s not a discovery and right in the spec,
Sadly those are very rare so you almost always need to use a more common 256mb low density dimms at part capacity to make it work at partial density 64mb, it should be perfectly stable

EDO dimms are just easier to find in 64mb sizes that work on a VX than sdram dimms that are detected correctly @ 64mb

Would this allow you to boot with 2x256 sticks and have it detect and use 128MB on a VX?

Chadti99 wrote on 2021-03-08, 18:38:

rmay635703 wrote on 2019-04-19, 06:35:

A VX supports 32 chip low density 64mb SDRAM […]
Show full quote

A VX supports 32 chip low density 64mb SDRAM

It’s not a discovery and right in the spec,
Sadly those are very rare so you almost always need to use a more common 256mb low density dimms at part capacity to make it work at partial density 64mb, it should be perfectly stable

EDO dimms are just easier to find in 64mb sizes that work on a VX than sdram dimms that are detected correctly @ 64mb

Would this allow you to boot with 2x256 sticks and have it detect and use 128MB on a VX?

Yes,
Takes you right up to the VX 128mb memory limit.
I have seen that done back in the $9.99 PC133 sdram closeout days (turn of the century)

People forget the VX is literally so old that
1st Gen 5volt SDRAM was still on the market , you could buy 8mb dimms
20ns SDRAM was a thing
64mb sdram dimms did not exist in 1995 meaning the spec was stupid though a few made true low density dimms for Intel systems anyway
Some boards lacked proper 3.3volt memory support
And the VX being a value offering it was thought no one would ever need more than 64mb let alone the illogical configuration to take it up to 128mb and SDRAM was an afterthought and a gimmick with many VX boards not having dimm sockets anyway

Things changed rapidly and many chipset decisions for socket 7 turned out terrible like the TX and it’s poor SDRAM performance and terrible locked catchable memory limits.