This post has been based on my experiments done several months ago. Today I've done another research online and decided to run second set of experiments, to be sure. First, tried P24D setting on the original Vobis 1.04 BIOS and got black screen. Then tried the same setting with a BIOS from the Abit AH4 motherboard and voila, write-back enabled! I probably oversaw something before. The sad thing is relatively large amount of settings simply vanished from the BIOS screen, like the option to set L2 cachce to WT/WB mode. Still, I'm happy it works. Who knows, perhaps I'll be lucky and manage to obtain "true" CH-471B BIOS.

Two questions that come to my mind regarding this motherboard:

1. Is it possible that those missing BIOS options are simply hidden behind some key short-cut?
2. I remember that while testing several ISA sound cards with this board, some of them refused to work in the third slot from the bottom (e.g. Sound Blaster 16) even though they worked in the first or second slot from the top. ESS 1868 based card worked without a hitch in every slot. I don't know much about vintage motherboards but is it possible that some slots behave differently than others?

I have some updates on this topic.

1. I have managed to obtaing BIOS version 1.06 but have some trouble making it work with DX4 100MHz WB. First time it booted, next time (and everytime from there on) I'm getting a black screen. I am attaching it for archival sake (I don't know where else to put it). Maybe someone will find it useful.
2. Fortunately, I have learned that it is possible to hack Abit AH4 BIOS with Modbin (used 4.50.82). With that it's very easy to reactivate L2 mode option. So now everything works nicely.

Paar wrote on 2020-03-11, 20:11:

I have some updates on this topic.

1. I have managed to obtaing BIOS version 1.06 but have some trouble making it work with DX4 100MHz WB. First time it booted, next time (and everytime from there on) I'm getting a black screen. I am attaching it for archival sake (I don't know where else to put it). Maybe someone will find it useful.
2. Fortunately, I have learned that it is possible to hack Abit AH4 BIOS with Modbin (used 4.50.82). With that it's very easy to reactivate L2 mode option. So now everything works nicely.

Nice looking board. Are you going to upgrade the L2 cache to 1024kB? If yes, buy the 15ns types, the ones labelled with 10ns are most likely fakes (in best case the are 15ns ones).

Or they may be counterfeits that actually have a 10 ns response time...

Is there any practical use for so much L2 cache on this machine? I have 32 MB RAM and don't plan to upgrade it.

If you aren't going above 32 MB, then 1024K over 256K may offer a 2-6% performance boost, depending on the application.

Well, I am trying to squeeze as much juice as possible from my setup, even to gain at least 1 more frame per second in Doom, as this is my goal with it - it should be speedy enough to play Doom 1 engine games well. Currently the biggest drawback is the graphics card, which is Cirrus Logic 5429. It's not bad card but I want something a little bit faster. It's hard to find good VLB cards nowadays though, seems like hoarders took them all 😀. But the L2 cache could help. I'll try to upgrade it if I'll be able to find suitable SRAM chips.

Yeah, the price inflation and rarity for motherboards, graphics, and sound cards is staggering. As such, I've been considering if I should take this opportunity to invest liquid cash in the bear (stock) market, as its down more than 20% or more hardware, or computer hardware. It seems like gains on computer hardware may be outpacing and less risky than the stock market.

I think you can get the 128kx8 cache chips on aliexpress or alibaba.

Paar wrote on 2020-03-12, 07:45:

...Currently the biggest drawback is the graphics card, which is Cirrus Logic 5429...

Well, I've got the Cirrus Logic 5429 too.
You cannot go to 64 MB since the LFB is just below 64 MB.
I've limited my 486 running the 5429 to 48 MB.

Paar wrote on 2020-03-12, 07:45:

...It's hard to find good VLB cards nowadays though, seems like hoarders took them all 😀.

Especially the ET4000W32 incarnations.

feipoa wrote on 2020-03-12, 00:20:

Or they may be counterfeits that actually have a 10 ns response time...

good one 😁

I have two or three board of this in my stock pile too.

If i have some time for it (because iam busy with other motherboard problems (wants to getting a classic pentuim build running)

Then i will upload those here.

Robin4 wrote on 2020-03-14, 01:14:

I have two or three board of this in my stock pile too.

If i have some time for it (because iam busy with other motherboard problems (wants to getting a classic pentuim build running)

Then i will upload those here.

I know there is some where VBS 1.08 bios floating around.

This is very nice and capable motherboard and deserves the best care 😊. I would certainly enjoy version 1.08, just for the heck of it. I would be glad if you're able to upload it.

feipoa wrote on 2020-03-12, 08:23:

Yeah, the price inflation and rarity for motherboards, graphics, and sound cards is staggering. As such, I've been considering if I should take this opportunity to invest liquid cash in the bear (stock) market, as its down more than 20% or more hardware, or computer hardware. It seems like gains on computer hardware may be outpacing and less risky than the stock market.

I don't know if retro parts are as liquid or have as many buyers as the share market, but in the longer term say 5 years it would be very interesting to see the gains side by side

There surely is profit to be made but it depends from where you buy the parts. I am lucky that in my country the parts are relatively cheap and I have an option to buy hardware from another two neighbour countries which are even cheaper. If I had to buy everything from eBay I wouldn't be so sure about that. It is however possible to buy some things on eBay for decent price from time to time.

the thing I notice with ebay there is alot of parts at very high prices but they don't sell quick, so its good if you buy cheap for collecting but selling it at a profit may not be a quick transaction

Very interesting! I have the same board with VBS 1.06 dated 01/11/95 but the dump is slightly different. Only by a few bytes, and a lot of that's text, so I'm not sure it's significant. Did you upload the original or was this already modbin-ned?

I'm also looking for a BIOS update, mainly because mine has the Y2K bug, although I'd like to fit a WB-enabled CPU some time too. I'd also heard of using the AH4 BIOS - did you manage to get all the options back and would you mind uploading your version if it's working?

Also: I'm guessing the BIOS is on that EPROM and not flashable? I have a programmer but no eraser, so it'd be good to get this done in one shot.

You're right, your dump is slightly different. I've tried to open it in Modbin and got checksum error, so it's highly probable that your dump is corrupted. Those EPROMs are rather old nowadays and could start losing the stored information. My dump (got it from a seller that offered this board in auction) checks fine. I'm including the AH4 BIOS I'm using. It's internal structure is somewhat different, probably to compensate for new CPU information or so. Almost all options are available, the main missing option is L2 cache mode as stated in my previous posts. I've made a quick mod that incorporated hiding "Memory hole" option and enabling "L2 cache mode". Memory hole is unnecessary as it apparently is used only with old VGA cards that need access to specific memory address region. If you want it differently you would have to make your own mod as I'm satisfied with it.

cosam wrote on 2020-03-14, 16:40:

Also: I'm guessing the BIOS is on that EPROM and not flashable? I have a programmer but no eraser, so it'd be good to get this done in one shot.

You need UV light to erase that chip. Either you have specialized device that will erase within a an hour or so, or you could leave it outside for a week so a sun shines directly on it. Once it's erased you can program it however you want.