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VIAFSB - DOS FSB utility for VIA chipsets

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Reply 60 of 70, by havli

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enaiel wrote on 2022-04-02, 01:27:

We're able to actually communicate with the PLL now and get back the FSB, so that's much better. Made some minor changes to the last few bytes we're sending based on default values from the datasheet. If that doesn't work, then I'm officially out of ideas as everything looks exactly like in the datasheet.
Please try to set the FSB to 130 first, and if that works, then try 111.

Thanks for testing!

Tried the version 0.2.0 and unfortunately not much luck. This time there are not artifacts, just good old freeze 😁 when trying to set the new FSB value. Tried the 130 MHz as you suggested. Well, I guess we can just leave it. The range of available FSB would be pretty limited anyway (originally I hoped for 66 MHz, so CPU az 266 MHz)... which is not possible. And there are other ways of reducing the speed if needed.

Btw - before I started testing, I was able to reach around 1GB/s memory copy bandwidth in Aida64. Now it maxes out at 700 or so MB/s. Perhaps some bit changed by accident in the cmos memory that alters memory settings? Many restarts and shutdows cycles didn't help. Not evel loading optimized defaults in BIOS. I will open the case and do clear cmos, that should definitely restore factory settings and the corect bandwidth.

Not that it matters anyway (for DOS gaming), but it bugs me that I remember the performance used to be better and now I can't reach it again. 😁

HW museum.cz - my collection of PC hardware

Reply 61 of 70, by Grem Five

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enaiel wrote on 2022-04-06, 03:49:
Can you please run VIAFSB with the dump option? […]
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Grem Five wrote on 2022-04-06, 02:08:

I have not had any luck with the winbond machines

As you can see from pics viafsb isnt showing right FSB just loading the pll

I noticed on this one it says Detected VT82C596A southbridge when its actually a VT82C596B I dont know if that has anything to do with the error or not.

Can you please run VIAFSB with the dump option?

VIAFSB [pll_name] [fsb_freq] -d > dump.txt

The dump file will tell me what it's actually reading. Thanks for testing!

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  • Filename
    DUMP2.TXT
    File size
    4.98 KiB
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    43 downloads
    File license
    Fair use/fair dealing exception
  • Filename
    DUMP1.TXT
    File size
    2.81 KiB
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    38 downloads
    File license
    Fair use/fair dealing exception

Reply 62 of 70, by GigAHerZ

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enaiel wrote on 2022-04-04, 20:08:
Maybe there is someone on Vogons who can figure out what I'm doing wrong? […]
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GigAHerZ wrote on 2022-04-04, 18:29:
Here it is. Getting the fsb as you suggested, did lock up the machine and the dump file is empty. […]
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Here it is.
Getting the fsb as you suggested, did lock up the machine and the dump file is empty.

Uploaded the dump of trying to set fsb to 75 with correct pll.
Hope it helps, let me know, if i can add anything.

Maybe there is someone on Vogons who can figure out what I'm doing wrong?

Here's the PLL W124 datasheet: https://www.datasheets360.com/pdf/-4213003440200208478

Here's what I'm writing to the PLL:
W124: Writing FSB_BYTE(3) (hex bin): 18 00011000
W124: Writing 7 bytes (hex): 00 00 00 18 45 EF 23

Based on the datasheet:

  • The PLL is write-only
  • Need to write 7 data bytes
  • First 3 data bytes are ignored
  • The 3rd data byte (starting from 0) is the FSB_BYTE
  • In the FSB_BYTE, Bit 3 (starting from 0) is the FS_SEL bit, needs to set indicating that the FSB is being set by software.
  • In the FSB_BYTE, Bits 4, 5, 6 need to be set as (0 0 1) to set the FSB to 75 as per the FSB frequency table in the datasheet.

The other possibility is maybe that W124G is actually different from W124? Can you try using SetFSB, SoftFSB, or CPUFSB in Windows and see if they support it? They may provide some additional information.

At last i got to this. I didn't have any windows setup for that yet, so i made a fresh win98 install for it.

Using CPUFSB and manually selecting "W124 A" (Because there was no "G") and setting fsb to 75MHz worked and is confirmed by CPU-Z. So it should be software controllable... somehow...

EDIT: "W124 B" works identically - 75MHz and 83MHz options work and are confirmed by CPU-Z.

"640K ought to be enough for anybody." - And i intend to get every last bit out of it even after loading every damn driver!

Reply 63 of 70, by Socket3

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I tried VIAFSB on my K6-2+ system witch uses an Aopen AX59 PRO motherboard with the MVP3 + 82C586B southbridge. Got "ERROR - Unknown Southbridge".

It would be awesome if you could get the utility to work with MVP3 motherboards - we could change the FSB from 100 to 66Mhz or maybe lower on the fly, without having to open up the computer...

Reply 67 of 70, by enaiel

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Sorry for not responding earlier, Real Life got in the way, unfortunately. I am going to upload the code to Github so that anyone can continue to add support for new PLL chips. I am refactoring the code to make it easier to do this by following some Linux code, so I would have to make the license GPL. I will update when the Github project is ready.

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Reply 68 of 70, by e8root

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I just tested this utility on this fabulous machine
847518_1683272558100.png

VIA C3 Nehemiah 800MHz
I wanted to be able to decrease its performance to around 386 levels for older games and more flexibility for 486 and 586 levels.
SetMul utility allowed me to disable caches, branch prediction and drop multiplier to 4x but it was still more like 486 than 386

ViaFSB allowed me do go down to 66MHz FSB bus and get performance similar to 386DX40
FSBs can be controlled from 66MHz to 166MHz giving much needed performance granularity.

Big thanks for this amazing utility!

Reply 69 of 70, by Bruno128

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Hi could you please add support for ICS950405AF. Thank you!
P.S. I can't find a GitHub that you mentioned.

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    ICS950405.PDF
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    datasheet 950405
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Reply 70 of 70, by tauro

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Amazing project! 🥳

I've tried it on an EPIA TC 10000, which has an ICS950908BF.
VIA C3 1GHz CPU, and CLE266+VT8235M
The default FSB is 133MHz and there's no way to change it on the BIOS menu.

Unfortunately VIAFSB didn't work. All possible clocks freeze the computer.
I attach one log here https://pastebin.com/4ZL48sVV

Hopefully you can fix it.

Thanks for your efforts 🙌