Reply 20 of 21, by Chkcpu
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CoffeeOne wrote on 2023-05-07, 18:46:Hi Jan, may I ask an off-topic question. You patched a lot of BIOSes, so I would like to know the following: […]
Hi Jan, may I ask an off-topic question.
You patched a lot of BIOSes, so I would like to know the following:Many "modern" 486 BIOS have LBA support, but they do have a 7.8GB Bios limit (something a bit below 8GB I believe).
I am talking of the Asus VL/I-486SV2GX4 and the Asus PVI-486SP3, I have those 2.
Would it be possible to overcome the 8GB limit with a modified Bios?
Hi CoffeeOne,
I agree the “modern” socket 3 and early socket 5/7 BIOSes would be a good candidate for such a patch, provided there is enough unused space in the ROM to add the code.
Alas, I never modified a BIOS to break the 8GB HDD barrier.
As you probably know, this mod would involve adding the IBM/Microsoft Int 13h extensions to the Int 13h interface. As the BIOS Interrupt 13h handler is already a very complicated piece of code, I’m afraid such a mod is way beyond my expertise. 😉
As < 8GB mechanical drives are unobtanium these days, and many people are using CF or SD cards now with the smallest new-bought sizes being 16 GB or larger, this is a real problem for pre-1998 machines.
Luckily we have the XTIDE Universal BIOS now which can be used to break the 8GB barrier, and this is what I’m using on my systems with a 1997 or earlier BIOS.
That said, when you do have an 8GB or smaller drive, that storage space is usually more than enough for these retro machines. DOS 5/6 and Windows 3.x don’t support more than 8GB drives anyway, but OSes like Windows 9x/DOS 7.x and NT4 with SP4 do.
Cheers, Jan