Do you need 64MB for anything specific? More RAM (ICs) adds noise to the board not capacitance... and worsens ability to overclock?

I used to have a VL-I-486SVG0. Version 1.2. You can use both 30pin SIMMS and 72pin SIMMS together. There should be a labelling on the board (to the left of the 85C407 IC) telling you to move an RN (resistor network).

But if you're going for speed, try one 16MB 72pin SIMM. Quake and Doom will load from the HDD no matter how much RAM you have. In which case it's worth trying to speed up HDD random read/write. The XT-IDE bios combined with a CF card will give you that...

I use 256 MB (2x 128 MB) FPM in a Shuttle HOT433.
1024 kB cache in write through mode. 2-1-1-1 @ 40 MHz FSB

MikeSG wrote on 2024-02-19, 12:38:

Do you need 64MB for anything specific? More RAM (ICs) adds noise to the board not capacitance... and worsens ability to overclock?

I used to have a VL-I-486SVG0. Version 1.2. You can use both 30pin SIMMS and 72pin SIMMS together. There should be a labelling on the board (to the left of the 85C407 IC) telling you to move an RN (resistor network).

But if you're going for speed, try one 16MB 72pin SIMM. Quake and Doom will load from the HDD no matter how much RAM you have. In which case it's worth trying to speed up HDD random read/write. The XT-IDE bios combined with a CF card will give you that...

I'd like 128MiB for Win95 and older Linux tinkering.

Each input to the DRAM IC adds capacitance which would reduce the slew rate, which could be detrimental to stability when pushed to limits.

I find the 85C471's RAM speed settings affect performance quite a bit. I can achieve "Fastest" up to 43MHz, "Faster" up to 49MHz, "Slower" up to 60MHz but that prevents me using the fast MWDMA VLB IDE.
The MWDMA IDE with a 512M CF and no BIOS extension gets the same score in DOOM as a RAMdisk. The score drops a bit when switching to a PIO4 IDE card, but the DTC one I have is happy over 50MHz.

What I'm going for is modifying the BIOS to flip the register bit to support modules that need A11 (64MiB 72pin, 128MiB 72pin, 16MiB 30-pin).
I've made a set of 39ns 16MiB 30-pin modules using speed-binned ICs. They currently must be limited to 4MiB. (In fact, the board wouldnt't post with them jumpered to 16MiB, because A11 is floating on this board).

I might start here: DIY Bios Modding guide Jan Steunebrink k6-2+/3+ 128gb

Il start with my standard line: "486 is not able to effectively use more than 16MB of ram anyway, anything requiring more will run bad and should be done on at least Pentium" 😀

nztdm wrote on 2024-02-19, 11:24:

I bodged on an Si5351 module and Arduino Nano to allow any bus speed.

nice

nztdm wrote on 2024-02-19, 11:24:

The SiS 85C471 chipset supports 128MB, but this isn't implemented on this board. Setting that register to 1, will change that pi […]
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The SiS 85C471 chipset supports 128MB, but this isn't implemented on this board.
Setting that register to 1, will change that pin function to MA11 (A11 for RAM).
MODBIN shows the BIOS as having register 50, bit 2, set to 0 by default.
Changing this to 1 in MODBIN doesn't work either. I suspect you need to do something else to the BIOS to get this change to stick...

I see two options.
1 disassembly of the bios and carefully following ram initialization. Something to get you started https://github.com/raszpl/430FXL2Cache
2 trying suitably similar bios from another board supporting 128MB ram natively.

Disruptor wrote on 2024-02-19, 13:43:

I use 256 MB (2x 128 MB) FPM in a Shuttle HOT433.
1024 kB cache in write through mode. 2-1-1-1 @ 40 MHz FSB

is all 256MB cached, or lower half?

rasz_pl wrote on 2024-02-19, 15:23:

Disruptor wrote on 2024-02-19, 13:43:

I use 256 MB (2x 128 MB) FPM in a Shuttle HOT433.
1024 kB cache in write through mode. 2-1-1-1 @ 40 MHz FSB

is all 256MB cached, or lower half?

Since I use write through caching, all 256 MB is cached.

nztdm wrote on 2024-02-19, 11:24:

I've been having some fun with 486 overclocking. I have two boards, a Biostar MB-8433UUD, and an ASUS VL/I-486SVGOX4. […]
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I've been having some fun with 486 overclocking. I have two boards, a Biostar MB-8433UUD, and an ASUS VL/I-486SVGOX4.

The Biostar (BIOS UUD2014) is great, and is a well known board. It even POSTS and can run some of the DOOM benchmark running at 2x83=166MHz and one of the 2X-capable Am5x86 chips (Am486DX2-66V16BGC). But it has graphical corruption and instability (same CPU is stable at 3x60=180).
But even running at 4x40MHz with fastest RAM/cache, or 3x60MHz and fastest RAM and slowest L2 or disabled L2, it is unremarkable in DOOM, getting 1268 realtics, but good in Quake, getting 19.7 fps.

The ASUS (BIOS 0402.002) is odd, as it's Rev1.2, which has incomplete documentation, and somewhat incompatible jumper settings with the later revs. If you find the correct settings for your CPU, take a pic in case you can't find it again. Another board that is almost identical is the VL/I-486SV2GX4. I got nowhere with ASUS via email trying to find manual for the GO (or is it G0).
The board was the non-X4 version, so I added the missing parts.
I used a lower dropout regulator (MIC29302) rather than the correct part (LT1084), along with an adjustment trimpot for voltage. The lower dropout is needed for the 4.0-4.5V range.
I bodged on an Si5351 module and Arduino Nano to allow any bus speed.

TLDR:
The board supports up to 64MB RAM officially.
The SiS 85C471 chipset supports 128MB, but this isn't implemented on this board.
I wish to use this board for a build, as I have some nice VLB cards to go with it, and gets faster benchmarks than the Biostar PCI board.
I'd rather have at least 64MiB of RAM than 32MiB I'm currently stuck with. 2x32MiB modules is asking for trouble at overclock speeds as 32MiB 72-pin SIMMs are dual-bank, putting almost twice as much capacitance on the bus.
The RAM slots (both 72-pin and 30-pin slots) have A11 disconnected, limiting you to 32MiB 72-pin SIMMs and 4MiB 30-pin SIMMs. (Due to missing A11, SIMMs of 64MiB = 16MiB, 128MiB = 32MiB, 30pin_16MiB = 4MiB).

As per the datasheet page 23, pin 138 is RAS3 when register 50, Bit 2, is 0. This pin is unconnected on the board. (The chipset has up to 7 RAS's).
Setting that register to 1, will change that pin function to MA11 (A11 for RAM).

If I connect pin 138 to RAM slots A11, there is no change. The pin stays High always. (I may need to put A11 through an F245 buffer like A0-10 go through (buffers which have DIR and OE fixed to 5V and GND)).
MODBIN shows the BIOS as having register 50, bit 2, set to 0 by default.
Changing this to 1 in MODBIN doesn't work either. I suspect you need to do something else to the BIOS to get this change to stick...

Any other ideas? Perhaps another way to modify the BIOS.

Interesting thread for me, because I own both a VL/I-486SVGOX4 Revision 1.2 and a VL/I-486SV2GX4 Revision 2.0.
I found out the correct jumper setting for the SVGOX4 for Am5x86 L1 write back mode, it was really cumbersome:
Re: 2 questions about Asus VL/I-486SV2GX4
By the way, you know all that, because you particpated in the thread.

About the 64MB limit. It seems to apply to both the SVGOX4 and the SV2GX4.
I believe that is really a hardware related issue (some chipset pins not connected to SIMM slots or whatever) and cannot be fixed with a new Bios.
For the SV2GX4 it is even more annoying, because it has 4 72pin slots, so it would be super easy to insert 4 times 32MB SIMMs. Unfortunately it does not work. I would like to use 128MB RAM, too. With 1MB of L2 cache it would be still fully cached in L2 WB mode.

CoffeeOne wrote on 2024-02-19, 20:32:

Interesting thread for me, because I own both a VL/I-486SVGOX4 Revision 1.2 and a VL/I-486SV2GX4 Revision 2.0. I found out the c […]
Show full quote

Interesting thread for me, because I own both a VL/I-486SVGOX4 Revision 1.2 and a VL/I-486SV2GX4 Revision 2.0.
I found out the correct jumper setting for the SVGOX4 for Am5x86 L1 write back mode, it was really cumbersome:
Re: 2 questions about Asus VL/I-486SV2GX4
By the way, you know all that, because you particpated in the thread.

About the 64MB limit. It seems to apply to both the SVGOX4 and the SV2GX4.
I believe that is really a hardware related issue (some chipset pins not connected to SIMM slots or whatever) and cannot be fixed with a new Bios.
For the SV2GX4 it is even more annoying, because it has 4 72pin slots, so it would be super easy to insert 4 times 32MB SIMMs. Unfortunately it does not work. I would like to use 128MB RAM, too. With 1MB of L2 cache it would be still fully cached in L2 WB mode.

Yes 4 X 32M won't work as that's 8 banks of RAM which the chipset doesn't support. 4x64M is only 4 banks of RAM, even if half isn't used because of a hard 128M limit of the chipset. But A11 is needed for 64M SIMMs or they'll be seen as 16M (or not boot if A11 is floating).

I am certain a new BIOS isn't enough to fix the A11 issue. You actually have to wire A11 to the chipset (likely through an F245) which I have done. I just want to try flipping the correct chipset bit during RAM initialisation. Will read Jan's thread here and try look for instructions that set chipset register 50h.

nztdm wrote on 2024-02-19, 20:41:

CoffeeOne wrote on 2024-02-19, 20:32:

Interesting thread for me, because I own both a VL/I-486SVGOX4 Revision 1.2 and a VL/I-486SV2GX4 Revision 2.0. I found out the c […]
Show full quote

Interesting thread for me, because I own both a VL/I-486SVGOX4 Revision 1.2 and a VL/I-486SV2GX4 Revision 2.0.
I found out the correct jumper setting for the SVGOX4 for Am5x86 L1 write back mode, it was really cumbersome:
Re: 2 questions about Asus VL/I-486SV2GX4
By the way, you know all that, because you particpated in the thread.

About the 64MB limit. It seems to apply to both the SVGOX4 and the SV2GX4.
I believe that is really a hardware related issue (some chipset pins not connected to SIMM slots or whatever) and cannot be fixed with a new Bios.
For the SV2GX4 it is even more annoying, because it has 4 72pin slots, so it would be super easy to insert 4 times 32MB SIMMs. Unfortunately it does not work. I would like to use 128MB RAM, too. With 1MB of L2 cache it would be still fully cached in L2 WB mode.

Yes 4 X 32M won't work as that's 8 banks of RAM which the chipset doesn't support. 4x64M is only 4 banks of RAM, even if half isn't used because of a hard 128M limit of the chipset. But A11 is needed for 64M SIMMs or they'll be seen as 16M (or not boot if A11 is floating).

I am certain a new BIOS isn't enough to fix the A11 issue. You actually have to wire A11 to the chipset (like through an F245) which I have done. I just want to try flipping the correct chipset bit during RAM initialisation. Will read Jan's thread as linked before.

download/file.php?id=133625&mode=view
4 times 32MB double sided SIMMs is supported according to the SIS471 chipset documentation.

CoffeeOne wrote on 2024-02-19, 20:44:

nztdm wrote on 2024-02-19, 20:41:

CoffeeOne wrote on 2024-02-19, 20:32:

Interesting thread for me, because I own both a VL/I-486SVGOX4 Revision 1.2 and a VL/I-486SV2GX4 Revision 2.0. I found out the c […]
Show full quote

Interesting thread for me, because I own both a VL/I-486SVGOX4 Revision 1.2 and a VL/I-486SV2GX4 Revision 2.0.
I found out the correct jumper setting for the SVGOX4 for Am5x86 L1 write back mode, it was really cumbersome:
Re: 2 questions about Asus VL/I-486SV2GX4
By the way, you know all that, because you particpated in the thread.

About the 64MB limit. It seems to apply to both the SVGOX4 and the SV2GX4.
I believe that is really a hardware related issue (some chipset pins not connected to SIMM slots or whatever) and cannot be fixed with a new Bios.
For the SV2GX4 it is even more annoying, because it has 4 72pin slots, so it would be super easy to insert 4 times 32MB SIMMs. Unfortunately it does not work. I would like to use 128MB RAM, too. With 1MB of L2 cache it would be still fully cached in L2 WB mode.

Yes 4 X 32M won't work as that's 8 banks of RAM which the chipset doesn't support. 4x64M is only 4 banks of RAM, even if half isn't used because of a hard 128M limit of the chipset. But A11 is needed for 64M SIMMs or they'll be seen as 16M (or not boot if A11 is floating).

I am certain a new BIOS isn't enough to fix the A11 issue. You actually have to wire A11 to the chipset (like through an F245) which I have done. I just want to try flipping the correct chipset bit during RAM initialisation. Will read Jan's thread as linked before.

download/file.php?id=133625&mode=view
4 times 32MB double sided SIMMs is supported according to the SIS471 chipset documentation.

Yes 8 banks is the max supported if all multipurpose pins are configured to be RAS's. On this board, I don't think that's the case.
Getting A11 to work is taking one of the RAS's for a start (one that isn't wired up on my board tho, as only 5 banks are possible on a board with two 72-pins and four 30-pins).

nztdm wrote on 2024-02-19, 20:47:

CoffeeOne wrote on 2024-02-19, 20:44:

nztdm wrote on 2024-02-19, 20:41:

Yes 4 X 32M won't work as that's 8 banks of RAM which the chipset doesn't support. 4x64M is only 4 banks of RAM, even if half isn't used because of a hard 128M limit of the chipset. But A11 is needed for 64M SIMMs or they'll be seen as 16M (or not boot if A11 is floating).

I am certain a new BIOS isn't enough to fix the A11 issue. You actually have to wire A11 to the chipset (like through an F245) which I have done. I just want to try flipping the correct chipset bit during RAM initialisation. Will read Jan's thread as linked before.

download/file.php?id=133625&mode=view
4 times 32MB double sided SIMMs is supported according to the SIS471 chipset documentation.

Yes 8 banks is the max supported if all multipurpose pins are configured to be RAS's. On this board, I don't think that's the case.
Getting A11 to work is taking one of the RAS's for a start (one that isn't wired up on my board tho, as only 5 banks are possible on a board with two 72-pins and four 30-pins).

OK, please keep us updated how you are progressing.
One silly last question: You have 2 times 64MB FPM modules that you can use for the board? 64MB FPM SIMMs are pretty rare.

CoffeeOne wrote on 2024-02-19, 21:35:

nztdm wrote on 2024-02-19, 20:47:

CoffeeOne wrote on 2024-02-19, 20:44:

download/file.php?id=133625&mode=view
4 times 32MB double sided SIMMs is supported according to the SIS471 chipset documentation.

Yes 8 banks is the max supported if all multipurpose pins are configured to be RAS's. On this board, I don't think that's the case.
Getting A11 to work is taking one of the RAS's for a start (one that isn't wired up on my board tho, as only 5 banks are possible on a board with two 72-pins and four 30-pins).

OK, please keep us updated how you are progressing.
One silly last question: You have 2 times 64MB FPM modules that you can use for the board? 64MB FPM SIMMs are pretty rare.

Yes I have some 128MiB FPM SIMMs.
Right now, the system won't boot with them installed because A11 is left floating.
But if I connect A11 to a defined state (GND or 5V or chipset pin 138), it boots and I can use 32MiB per module which makes sense with a non-working A11.
I know I'll have succeeded if I can get the RAM count for a single module to show more than 32M. I know that if I get it to show 64M, then A11 is working but there is another hard limit in the BIOS.