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Changing the BIOS chip on a motherboard?

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First post, by ShovelKnight

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Hi,

I noticed there are some motherboards that were sold in 2 versions: with a 1 Mbit BIOS chip and with a 2 Mbit BIOS chip. Usually these motherboards have some sort of later/enhanced BIOS (e.g. with 128GB HDD support) which is available only for the 2 Mbit version.

If I get such a motherboard, would it be possible to simply replace the BIOS chip? For example, I could buy an SST39SF020 or any other 5V 2 Mbit flash chip, flash it with a TL866 programmer and install it in place of the original 1 Mbit BIOS chip. Would it work?

Last edited by ShovelKnight on 2019-08-15, 13:36. Edited 1 time in total.

Reply 1 of 4, by dionb

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If the only difference is the BIOS size: yes.

Sometimes though the larger BIOS is related to other changes between revisions (different sound or I/O chips etc), in which case it probably won't work. But if unsure, no harm in trying - you still have your original BIOS and you can always re-flash the 2Mb EEPROM for another board if it fails. Just make sure you line up the chip correctly - only way I ever smoked a board messing with BIOS was the time I accidentally got the chip the wrong way round...

Reply 3 of 4, by GigAHerZ

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It is recommended that you fill the larger chip.

So if you have 2Mb chip and 1Mb ROM, put the ROM in twice: one from the beginning and one from the middle.
This protects you from the case when the upper address lines may behave in unknown way - you just don't care, if your chip is full as described.

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

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