You can double video-ram for a total of 2MB by populating the two "zippy" sockets.

Mine is rev. A also and the BIOS I dumped is 1026...

majestyk wrote on 2025-04-19, 17:22:

You can double video-ram for a total of 2MB by populating the two "zippy" sockets.

Mine is rev. A also and the BIOS I dumped is 1026...

i think these would just add some high res modes, but maybe perfomance will be improved a little by having more room for video pages.

Hi, a little update.

I upgraded cache to 256 KB, ordered 10 UMC 32x8k two weeks ago. The perfomance increase was not much but noticeable, it feels snappier. CPU score was mostly the same, speedsys reported 24.4 pts and topbench an overall of 205 (no changes at all).

On FastDoom 1.13 benchmark i get 34.5 FPS avg.
LM60 - 316 MHz AT
3DBench - 45.4 FPS

Your Cachechk scores for internal and external cache are in line with a fully tuned 486DX2-66 system. However, the memory speed is bad.
Something you can do is temporarily disable external cache, and run Cachechk again. If the memory scores improve, it's an Always Dirty issue (should not be an issue on this board). If they don't, it's untuned RAM wait states.

There is a FIC 4386-VC-HD BIOS with many more options, but I don't know if it would be compatible with your board.

The 486VAV has separate TAG- and dirty-TAG chips (10 chips in total) so a "dirty-issue" _should_ not apply.

jakethompson1 wrote on 2025-04-23, 03:47:

Your Cachechk scores for internal and external cache are in line with a fully tuned 486DX2-66 system. However, the memory speed is bad.
Something you can do is temporarily disable external cache, and run Cachechk again. If the memory scores improve, it's an Always Dirty issue (should not be an issue on this board). If they don't, it's untuned RAM wait states.

There is a FIC 4386-VC-HD BIOS with many more options, but I don't know if it would be compatible with your board.

Gotta give a try after work, and about the bios swapping, the issue is that the video bios is on the same chip that is the system bios, maybe by just merging them together and keeping the offsets would work.

bloodbath2you wrote on 2025-04-23, 12:16:

jakethompson1 wrote on 2025-04-23, 03:47:

Your Cachechk scores for internal and external cache are in line with a fully tuned 486DX2-66 system. However, the memory speed is bad.
Something you can do is temporarily disable external cache, and run Cachechk again. If the memory scores improve, it's an Always Dirty issue (should not be an issue on this board). If they don't, it's untuned RAM wait states.

There is a FIC 4386-VC-HD BIOS with many more options, but I don't know if it would be compatible with your board.

Gotta give a try after work, and about the bios swapping, the issue is that the video bios is on the same chip that is the system bios, maybe by just merging them together and keeping the offsets would work.

You should be able to replace the last 64K of your ROM image with whatever BIOS you want.
The issue would be if there are multiple revisions of your VIA chipset, and perhaps yours is missing those settings (even as hidden options) for good reason, like if they aren't supported.

you should use a DX cpu if at all possible, even a good old inexpensive intel dx2 would do. To me it wouldn't make much sense to max out the cache but to keep using a SX cpu.

also, if there is any way to set the board to run the fsb at 40mhz that would be the way to go

bertrammatrix wrote on 2025-04-23, 17:37:

you should use a DX cpu if at all possible, even a good old inexpensive intel dx2 would do. To me it wouldn't make much sense to max out the cache but to keep using a SX cpu.

also, if there is any way to set the board to run the fsb at 40mhz that would be the way to go

Yes, i even used a DX-33 overclocked to 40, i can also fit any crystal on the same PLL socket, i think the board can go up to 50 MHz. i ordered 100 and 120 MHz crystals to give a try.

Ok, tried with a different bios from this board:

https://theretroweb.com/motherboards/s/fic-486-vc-hd#bios

it has both ami and award, tested the award one, version 1.10K, first with the GD5428 + Award bios it worked but got no video, maybe the original ami bios sets the onboard video on boot. So, i picked up a crappy 8 bit VGA card for video output and did some perfomance measures.

As you can see, the award one is even worse, feels older and more basic than the ami one, no auto HDD detection, no rom shadowing options, no fast a20 gate... it has a cache speed option btw, tried with two of three options, NORMAL and TURBO.

Turbo:
Cachechk reports 18.9 MB/s memory speed,
Speedsys reports 44.20 MB/s memory bandwidth

Normal:
CACHECHK reports 16.6 MB/ memory speeds
Speedsys reports 36.67 MB/s memory bandwidth

Topbench reported 60 something points comparable to a 386DX40 machine but is due to the bad video card so is understandable, after all i had no expectations on this bios. I think i'm reaching a ceiling but i'd try hacking the AMI bios in future and any suggestions will be very appreciated.

i went back to the AMI 1.026A bios but took advantage of time to update the GD542x bios version from 1.30 to 1.41, any advantages doing this? dunno but why not.

VIA chipsets from that time often have poor memory performance. Most (all) BIOSes increase waitstates as soon as CPU frequency and/or FSB go up and you cannot overrule it by adjusting BIOS settings. I had several cases where memory performance was better(!) with slower CPUs /FSB).
All you can do is max out L2 cache and make sure all installed mamory is being cached.

majestyk wrote on 2025-04-26, 05:47:

VIA chipsets from that time often have poor memory performance. Most (all) BIOSes increase waitstates as soon as CPU frequency and/or FSB go up and you cannot overrule it by adjusting BIOS settings. I had several cases where memory performance was better(!) with slower CPUs /FSB).
All you can do is max out L2 cache and make sure all installed mamory is being cached.

Found it! Found a good bios. Taken from this board:

https://theretroweb.com/motherboards/s/fic-486-vc-hd#bios

BIOS 1.021

Has all options i need

- Bus speed options
- Cache timings
- Memory timings

Made a new rom with the latest Cirrus Logic bios CL-GD542X Bios v1.41 + Version 1.021 and worked perfectly.

Set all memory and cache timings to the fastest , AUTOCONFIG disabled and did some measures. Also tried at 40 MHz fsb which, with the latest bios the board won't even post, crazy.

At 33 FSB, max memory and cache settings.

TOPBENCH - 219 score
SPEEDSYS - 53.94MB/s memory bandwidth, 24.67 MB/s troughput
LM60 - 316 MHz AT
DOOM -35.5 FPS
3DBENCH - 50 FPS
CACHECHK - 22.2 MB/s main memory speed

At 40 FSB, max memory and cache settings.

TOPBENCH - 257 score
SPEEDSYS - 65.7 MB/s memory bandwidth, 29.78 MB/s troughput
LM60 - 380 MHz AT
DOOM - *CRASH*
3DBENCH - 58.8FPS
CACHECHK - 26.6 MB/s main memory speed

It was stable until ran doom, duke3d runs and is playable for 20 mins until crashes. Maybe i'll mod the board and add more bypass caps around the CPU socket for reducing the current noise.

captures

Ok, the next i'll do is:
1. Try 50 MHz FSB with crystals.
2. Add more bypass capacitors.
3. Increase Video RAM to 2MB
4. Order a socket blaster PCB and put an Intel DX4-100.
5. Replace the onboard video chip with a GD5429 or 543X.
6. Set multiplier to 2X and use 50MHz FSB, if works, try 60 MHz.

I assume the VC-HD BIOS won´t support the SMC super-I/O?

majestyk wrote on 2025-04-26, 15:53:

I assume the VC-HD BIOS won´t support the SMC super-I/O?

Seems not because the FDC and HDD are working fine, havent tried serial and parallel ports yet.

Update: Added a bunch of bypass capacitors on the socket for a total of ~36uF, 18 x150nF and one 10 uF.

FDoom now is stable and got 42 FPS at 40 MHz FSB.

Update:

- Built a 486 Socketblaster + Intel DX4WB
- Built a custom PLL

The custom PLL based on the ICS501 LOCO made able to play with weird clocks, using a 16.9344 MHz base clock.
- 42.5 FSB 2x Multiplier : Stable
- 42.5 FSB 3x Multiplier: POSTED but very unstable.
- 45 FSB 2x Multiplier: This one is the most i tinkered with, felt very stable giving 90 MHz
TOPBENCH : 300 Pts
3DBENCH - 66.6 FPS
- 45 FSB 3x : No past post, i think it needs more CPU voltage.
- 50 FSB: No video.

All tests were on 3.78 VCORE, for overclocking i think is the max this CPU could handle.

Anyways, the socketbaster is not complete yet, i need to solder the missing SMD capcitors on the bottom. This could be a big difference on stability.

I'll post more measures if you are interested, i did everything on a run this moring, even the custom PLL so many tests were not done.