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Reply 20 of 37, by Jolaes76

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In my experience, in most cases yes, but not always.
I met motherboards in the past that were sowehow picky about brand, where the internal arrengement and even speed rating of the chips were the same. The motherboard would boot with the SST but not the Texas etc.
(For cross-checking, I reprogrammed the EEPROM with another BIOS and put it in an other motherboard and it was working there.)

This is strange in light of the fact that readout voltage is standard for these EPROMs and EEPROMs, it is the programming voltage and stablility that can vary to a great extent. Some chips, especially old (window-type) EPROMs need more juice than prescribed and a finely calibrated burning. (THOSE are the ones you need a higher-end burner for, not some Chinese crap)
AFAICR, there were some weird EEPROMs in my possession as well that behaved the exact same way.

All in all, if you have a decent motherboard like this, you have a good chance that it will work with a variety of compatible EEPROMs.

"Ita in vita ut in lusu alae pessima iactura arte corrigenda est."

Reply 21 of 37, by feipoa

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I am not sure about any EEPROM. This board uses a 512 kbit EEPROM, which has 28 pins. Most later 486 and Pentium boards come with EEPROM's which have 32 pins and are 1024 kbit.

While this 486SV2GX4 board has solder pads to allow you to solder in a 32-pin DIP, I haven't confirmed that a 1024 kbit BIOS will work. I tried this experiment on a PC Chips M912 motherboard, which also comes with a 28-pin DIP BIOS, but I could not get a 32-pin EEPROM BIOS to function. Only the 28-pin EEPROM BIOSes work.

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Reply 22 of 37, by Jolaes76

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I swapped EEPROMs and EPROMs between (S) Socket7 boards that have the 32 leg DIP sockets by default, and it mostly works there - although a big EPROM like this cost quite a bit and is erased / programmed quite slowly 🙁
I do not have much experience with 486 boards with EEPROMs.

So it seems this particular Asus board is a no-go.

"Ita in vita ut in lusu alae pessima iactura arte corrigenda est."

Reply 23 of 37, by mt777

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I tested several options to maximize results.
Bios from EFA 4DMS works but performance is much worse than original from Asus.

Cyrix 120GP, 1MB cache.

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Reply 24 of 37, by techweenie

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feipoa wrote on 2015-12-22, 20:43:
I have been testing an Asus VL/I-486SV2GX4 motherboard. I have updated the board with the latest BIOS, 0402-1, which allows for […]
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I have been testing an Asus VL/I-486SV2GX4 motherboard. I have updated the board with the latest BIOS, 0402-1, which allows for running Intel/AMD/Cyrix DX4/5 chips in L1:write-back mode. No problem there. The problem is this BIOS version no longer has the option to set the L2 cache into write-through mode. The options are "Write-back" and "Auto". The "write-back" option slows the RAM throughput down nearly 3-fold, probably because the BIOS is incorrectly setting the Alter Bit. Setting the BIOS option to "Auto" correctly sets the L2 cache into write-back mode with the expected memory throughput. By the way, I am using 1024KB L2 cache with a 64kx8 TAG.

The problem is that I cannot figure out how to force the L2 cache into write-through mode. Any ideas?

Does anyone know of other SiS 471-based BIOSes with proper support for L1:WB mode I can try?

The Asus BIOS for this board also does not allow for using 4x32MB SIMMs for a total of 128 MB. For some reason, they limit you to 2x32 MB. If I try to install 4x32 MB FPM, the board doesn't show any signs of life. The chipset spec. sheet for the SiS 471 mentions that 128 MB is supported.

BIOS revision 0401 allows you to set L2 to WT and works with L1 WB. However, based on my testing, 0402 with L2 set to Auto is the same as WT mode. Benchmark results between that and 0401 L2 WT are identical. L2 WB enabled is equally bad performance on both versions. This motherboard is a big letdown performance-wise. I've been comparing it to the PC Chips M912 and that board is faster in every single game benchmark when equipped with the Award BIOS.

Reply 25 of 37, by feipoa

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Most likely because the dirty bit getting set incorrectly behind the scenes. I've seen many a board do this. I think there was another thread which addressed something of this nature. Someone did some hardware hack with the cache, but then we realised it could be solved via a simpler BIOS mod.

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Reply 26 of 37, by GigAHerZ

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I did a software hack and got the write-back L2 to work properly on same chipset: Re: 486 cache/ram speed issue with write-back

"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 27 of 37, by TheMobRules

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Here's the updated BIOS for the ASUS board using GigAHerZ's findings. It's the latest official version (0402.001) with a couple of bits swapped from 0 to 1 on register 72 to properly set L2 dirty tag:

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ASUS VL/I-486SV2GX4 modded BIOS "0402.002"
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Reply 29 of 37, by feipoa

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That was one of the threads. Wasn't there one other thread as well? I know I modified the BIOS in MODBIN as well, but in another thread by PC-Engineer, I think.

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Reply 30 of 37, by techweenie

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The modded BIOS works! Performance is right in line with where it should be, both with L1 WT and WB. The best combination is L1 WT with L2 WB. DRAM Write Burst doesn't work when L1 WB is enabled. It's now tied with the M912 as the fastest non-pci motherboard I've tested. They trade blows within <1% of each other.

Reply 32 of 37, by OzzFan

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What flash utility did you use? I'm having trouble locating the right one.

A (mostly accurate) listing of my computer systems: http://www.shelteringoak.com/OzzNet/

Reply 33 of 37, by mockingbird

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OzzFan wrote on 2021-01-15, 14:13:

What flash utility did you use? I'm having trouble locating the right one.

You won't fine a flash utility because the flash chip is an EPROM that needs to be erased with UV light and programmed externally.

7ivtic.png

Reply 34 of 37, by OzzFan

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mockingbird wrote on 2021-01-15, 16:21:
OzzFan wrote on 2021-01-15, 14:13:

What flash utility did you use? I'm having trouble locating the right one.

You won't fine a flash utility because the flash chip is an EPROM that needs to be erased with UV light and programmed externally.

Ah ok. I don't have one of those. So these aren't flashable EEPROMs? No chance of getting an image file?

A (mostly accurate) listing of my computer systems: http://www.shelteringoak.com/OzzNet/

Reply 35 of 37, by mockingbird

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OzzFan wrote on 2021-01-15, 20:00:

Ah ok. I don't have one of those. So these aren't flashable EEPROMs? No chance of getting an image file?

The image file would be the modded BIOS file posted a few posts up.

You can use a flashable EEPROM instead of an EPROM, namely the W27C512.

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Reply 36 of 37, by techweenie

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pshipkov wrote on 2021-01-15, 08:36:

How do you test it ?
I see wb+wb doing better.

I use the dosbench pack from Phil's Computer Lab. Keep in mind I'm testing with a SX955 DX2, not a DX4. The DX4 may have better cache optimizations.