I believe that many 486 motherboard did not have a flashable BIOS. This was a feature that was added a bit later on.

For motherboards that lack the capability to flash their BIOS, you have to pull the chip and reprogram it using an EEPROM programmer.

You could try it I guess but you might be unlucky enough that the flash software will erase/corrupt your BIOS but won't be able to program a new one.

So the BIOS chip found on the VLB 486 board can't be flashed, even if I insert it in to a PCI 486 mobo, that does have the ability to flash a BIOS chip - for the "hot flash technique"?

I guess the answer to my question above is: "no, this is not possible, in this case." And so I guess an EEPROM programmer is more powerful than the BIOS chip flash functionality found on more modern mobos, that are capable of flashing BIOS chips. So, I guess there is a difference between the verb "to flash" and "to reprogram".

So the BIOS chip found on the VLB 486 board can't be flashed, even if I insert it in to a PCI 486 mobo, that does have the ability to flash a BIOS chip - for the "hot flash technique"?

I've never actually tried that. Could be worth a shot....

RG, maybe this would be useful. You don't need to buy a programmer. My Zida Tomato 486 board also came with an outdated 1995 Award BIOS. It was one of those UV programmable EPROMs. I simply took a BIOS EEPROM chip from one of my dead mobos (a chip matching the size of the BIOS to be installed), and programmed it with the new BIOS in the same machine, using the method of hot-flashing.
The BIOS currently in your 486 can't be programmed in the mobo, because it's probably one of those UV EPROMs, which require a special ultraviolet flashing device or something like that.

This is very interesting information, thanks a lot. I decided to peel back the sticker on one of my spare BIOS chips. Underneath this sticker, I can now see a "mysterious looking little window". I wonder if this spare BIOS chip is a UV programmable EPROM? I could use it! I could put this spare BIOS chip inside the BIOS socket of the Asus VLB 486 mobo when it is switched on, and then attempt to hot flash it. What I now need to understand is - what Award flash utility shall I use? Would Flash465.com be a good suitable candidate? Or Flash52B.exe, or perhaps Awd66.exe?

Anyway, I could experiment. If it goes wrong, I will only break an old spare BIOS chip. And if I cannot hot flash it again, I could get a Willem programmer. BTW, I found a local seller for the Willem unit. The ebay advert is here. The writing seen on the spare BIOS chip says M27C512. Luckily, the Willem unit supports 27C512, which seems close enough, and in this ebay advert they call this type of chip "EPROM".

Edit: Sorry, I've got a bit confused - again! Do I hot flash the spare BIOS chip in a more modern board? Eg a 486 PCI board, that is capable of flashing a BIOS chip? Thanks a lot.

You can't flash UV EPROMs on a mobo socket. You need an ultraviolet device to do that.
You need an EEPROM (one which doesn't have that "window") to flash on that 486.
Notice the extra E in EEPROM, which means Electrically Erasable Programmable Read-Only Memory, which means can be flashed in socket without special programmers.
You have one EPROM, which have that window that require ultraviolet light to flash it.
You need a EEPROM, the ones without that window, found in most motherboards, which can be flashed using the motherboard socket. Maybe you can took one out from one of your dead mobos (if any) and use it with your 486.

EDIT: Sorry, but I think I missed something here. Does that mobo even have space in the BIOS socket to hold one of the 32-pin EEPROMs ?
My Zida came with one of those UV 28-pin EPROMs, but the socket was able to acommodate a 32-pin EEPROM, that's why it was so easy for me to update it, I simply have to replace the chip and reprogram, which I don't think is possible here because your mobo only have a 28-pin socket (DIP-28 ).

Ah, I see. Thanks for the info. Yes, you are right: the socket on the Asus VLB 486 can only accomodate a BIOS chip with 14 "legs" on each side of it, which is DIP-28. There is no extra room in this socket to insert a larger 32-pin EEPROM chip. I have some questions please:

* Is it possible to find a 28-pin DIP-28 EEPROM?

* I wonder if the Willem programmer is capable of programming UV EPROMs? My guess is yes it can, because it lists the 27C512 EPROM chip in the ebay advert, and this 27C512 chip has a little window in it.

Thanks a lot.

retro games 100 wrote:

* I wonder if the Willem programmer is capable of programming UV EPROMs? My guess is yes it can, because it lists the 27C512 EPROM chip in the ebay advert, and this 27C512 chip has a little window in it.

Thanks a lot.

It's likely to be able to, even if the pin count isn't right you can usually get an adaptor that the bigger chip will sit in. In terms of programming it, it will be fine, but you need something to erase it first.

I wonder if the Willem programmer is capable of programming UV EPROMs? My guess is yes it can, because it lists the 27C512 EPROM chip in the ebay advert, and this 27C512 chip has a little window in it.

What's to guess? It says it supports 27C512 chips, therefore it supports 27C512 chips. Those include both the UV erasable type, and the non-erasable type. Actually, I'm pretty sure that was the original purpose of its design... a cheap programmer for 27C series chips and similar.

As megatron-uk mentioned, you will need a UV eraser of some sort as well, if you're planning on reusing chips (which is a good idea, since the price of new ones will add up quick). But you can get erasers [url=http://cgi.ebay.com/UV-Eprom-Eraser-Erase-Ult … =item563cd05cdd]cheap[/i], they're nothing fancy but they'll work for small-scale hobbyist purposes.

Thanks a lot for everyone's advice! ATM, I am a bit concerned at the escalating cost of this operation. ATM, I just want to upgrade one chip. Therefore, I have emailed a bios repair company in the UK, and asked them if they can help me.

Depending on their response, I will either pay them about £10 (about $15) for this one-off operation, or if they can't help me, I will buy both the Willem unit, and also see if I can find someone in the UK who can sell me a UV eraser, with a UK mains plug on it. Electrical units from China might not work in the UK, and even if they did, items from China usually take several weeks to arrive. Thanks a lot people.

While I decide what to do about the BIOS, I removed the P75 CPU, and installed a POD83. I set the bus speed to 40, and I was surprised that Quake timedemo demo1 worked. I get 15.1 fps (in full screen), which is exactly the same score I got with the P75 @ 200 MHz! I get 65.whatever in Speedsys, but the memory timing scores aren't special, so I didn't bother including a screen shot. Basically I get 84, 54, 35. L1 seems to be write-through.

This is what I get with a P75@200MHz on this board.
All cache and memory related parameters were set to the lowest possible settings.

That's really awesome. Congratulations! Have you tried Quake timedemo demo1? That's a really good "over the top overclock" DOS stability test.

Edit: BTW, did you cut pin S4 on the P75 chip, in order to force 5V through it?

Unfortunately it is not stable enough to make further tests. The CPU runs only at 4V, at 5V I won't do anything. I think I have to find a better CPU...

I put a PGA-socket (desoldered from an old mobo, with the particular pin removed) between socket and CPU .

Excuse me for the off topic. In BastlerMike's speedsys screenshot, I see that we have the same hard disk, Maxtor 7245AT. I bought it second hand in 1993, and it still works flawless today!

Markk wrote:

Excuse me for the off topic. In BastlerMike's speedsys screenshot, I see that we have the same hard disk, Maxtor 7245AT. I bought it second hand in 1993, and it still works flawless today!

That's what we really like to hear! 😀 Good quality retro components providing useful service after a long period of time.

This is a question to any Asus VL/I 486SV2GX4 revision 2.1 owners, including BastlerMike and Amigaz! 😀 What BIOS file do you have in your mobo's BIOS chip? Is it (1) or (2)?

(1) BIOS 0402, File Size 45.28 (KBytes) 1996/10/15 update
(2) Beta BIOS 0402.001, File Size 45.31 (KBytes) 1999/12/21 update

I found these two BIOS files on the Asus website, inside the Socket 5 folder. BastlerMike, I noticed in your SpeedSys screenshot, that your BIOS file is dated 1997. That's interesting, because that date does not appear on the Asus website. Thanks for any info.

BTW, I have found a "bios repair dude" in the UK, and he has a spare suitable UV EPROM BIOS chip he can use. Friendly hint please people: I'm just waiting for confirmation about which BIOS file to use. Should I use (1) or (2) as seen in my post above, or is there a third BIOS file, dated 1997 which would be best?

As soon as I know which BIOS file to use, I can email it to him as an attachment. I'm itching to get started on this 200 MHz system again, this time hopefully with L1 write-back cache activated! Many thanks. 😀

Judging by the release date of the beta BIOS, I reckon it is the same as the older one, only with a Y2K patch applied.

5u3 wrote:

Judging by the release date of the beta BIOS, I reckon it is the same as the older one, only with a Y2K patch applied.

Yes, you must be right. I'm not bothered about a Y2K patch. I might just go for the 0402 (1996/10/15) file. Thanks.