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BIOS update - EPROM / Flash hot swap

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First post, by adalbert

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Hello, i would like to try updating my Abit PB4 rev 1.3 486 pci board because I have problems which I mentioned in different thread;
currently it has UV-erasable EPROM chip. I don't have other working mainboard with DIP36 socket, and I don't have a programmer, so I would like to do following procedure:

-Boot the board with Uniflash diskette
-Remove EPROM chip (hot swap)
-set the jumpers from 5V EPROM voltage to 12V Flash voltage
-Insert 1Mbit Flash chip i removed from other broken mainboard
-Program it with Uniflash
-keep the old EPROM as a spare part and use motherboard with new Flash chip.

But is that procedure safe? Can I replace EPROM with Flash while the motherboard is running?
I know that people often hot-swap same type of BIOS chips, but I don't know if I can mix the memory types and don't fry the board.

Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg

Reply 2 of 6, by adalbert

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Well, I have Etherlink III, it has 28 pin boot rom socket. I don't know it will work with 36 pin memory and remaining pins unconnected, i will do some research.

Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg

Reply 3 of 6, by alexanrs

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If the bios is big enough to need the higher address lines, I'd guess that it won't work. AFAIK the biggest danger of hot swapping is shorting something accidentally while replacing the chip. While I have not done it, one thing that might make hot swapping easier is to get the chip a bit loose while the board is off (but still making contact), and removing it once the boot process has been completed.

Reply 4 of 6, by shock__

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No it's not safe - as easy as that.

Finding someone with an appropriate programmer would be your best bet.

Also please link the other thread ... EPROMs rarely go totally bad (but can suffer from memory loss after some time).

Edit: Eurgh ... upgrading your BIOS seems pointless in regard to your issue. It's very likely a software issue somewhere in Windows.

Current Project: new GUS PnP compatible soundcard

[Z?]

Reply 5 of 6, by adalbert

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Here is older thread - Abit PB4 (486), ISA sound card - OK in DOS, not detected in Windows
ISA sound cards are not working in Windows - they are PnP devices and ESCD tables cannot be saved in EPROM so i think replacing bios with flash may help.
(Source: Re: Abit AB-PB4 for 486 build - same board)
I managed to install network card without PnP mode, but I cant disable PnP in my sound cards. I emailed local computer service, maybe they can program bios for me.

Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg

Reply 6 of 6, by smeezekitty

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AFAIK the biggest danger of hot swapping is shorting something accidentally while replacing the chip.

This. While it is possible, ROM sockets are not the easiest to work with and the chance of accidental shorts is fairly high.

I am about to buy an PROM programmer. For $50 the Chinese TL866 will do just about anything programmable.

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