I guess the BIOS is limited to 2 GB - pretty normal for a VLB 486 board.
I can't see any jumpers on those drives to limit capacity to 2 GB.
It may be possible to limit the drive's capacity to 2 GB using "Host Protected Area".

Your 486 is not compatible with HDD more than 2GB and 486's BIOS'es can not detect any optical drives. So... EVERYTHING OK)))

Hi jami3rez,

If the Award BIOS on your SY-025J is from 07/1994 or later, then it fully supports IDE drives up to 8GB! 😊

What you are seeing is the 2GB Harddisk display limit bug. This bug in 1994 and 1995 Award BIOSes limits the harddisk size display, on the BIOS Setup and boot screens, to 2015 MB.
Whenever a drive is 2016 MB or larger, the display starts to count from zero again. The same happens at 4032 and 6048 MB.
This looks a lot like an actual 2 GB limit but is only a cosmetic bug in the harddisk size display routine, and it doesn't affect the BIOS support for these larger drives.

For these Award v4.50(P)(G) BIOSes, just use the IDE HDD AUTO DETECTION selection from the Main BIOS menu to Setup the drive, select the option with LBA at the end, and disregard the incorrect HD size display.

If you want this bug fixed, I have an updated SY-025JKL Rev J.1 BIOS that fixes this cosmetic issue.
This updated BIOS also fixes the Year 2094 bug and adds support for faster CPUs. However, the BIOS on these 486 boards is stored in an UV-EPROM and can’t be flashed. So you need a spare 64KB (E)EPROM and an EEPROM programmer to be able to replace the BIOS.
Let me know if you are interested in this updated BIOS.

Cheers, Jan

I’ve actually been able to put a 10gb HDD on and it detects 2gb of useable space which it has formatted and I have installed MS DOS on it.

I’m not bothered about being able to use more, 2gb is fine by me.

I’m just confused why the other, smaller drives couldn’t use 2gb of their space and in the BIOS only saw 93mb and 487mb respectively?

I’m definitely interested in a BIOS update if that will smooth things over.

Babasha wrote on 2026-04-18, 17:17:

Your 486 is not compatible with HDD more than 2GB and 486's BIOS'es can not detect any optical drives. So... EVERYTHING OK)))

Well 2gb of useable space, which is fine, I don’t need to use the whole drive. My problem is the BIOS can only see 93mb of the 4.6gb drive and 487mb of the 2.6gb drive. I’ve since used a 10gb drive and it gives me access to 2gb. Why won’t it see 2gb on the smaller drives?

And good tip about the optical drive in the BIOS, I never actually realised that!

The core of the problem is that drive sizes got too big for the number of bits BIOS is looking at.... And BIOS was never designed to limit or allow overflow on numbers that would "never get bigger than expected", so you don't see the first 2G .. you see whatever remains after bit wrapping. Depending on the actual size of the drive, this could be thoretically amywhere between 1 sector and 2G.

A one point I had a BIOS extension that I put in the boot rom socket of a network interface card to resolve these problems, by supplying it's own HD driver code.

jami3rez wrote on 2026-04-18, 21:01:

I’ve actually been able to put a 10gb HDD on and it detects 2gb of useable space which it has formatted and I have installed MS […]
Show full quote

I’ve actually been able to put a 10gb HDD on and it detects 2gb of useable space which it has formatted and I have installed MS DOS on it.

I’m not bothered about being able to use more, 2gb is fine by me.

I’m just confused why the other, smaller drives couldn’t use 2gb of their space and in the BIOS only saw 93mb and 487mb respectively?

I’m definitely interested in a BIOS update if that will smooth things over.

Jan explained what is happening in the post above yours, the BIOS has a faulty display routine that resets when the size count goes over 2015MB. In the case of a 10GB drive, the capacity is limited to 8GB by the BIOS (usually about 8033MB) and the counter reset at 2016MB, 4032MB, 6048MB and the counter would finally rest on 1985MB giving the appearance of a ~2GB drive.

Accoring to Jan this is just a visual error and the drives that show up as 93~487MB should still format to their full capacity (subject to OS limits)

NeoG_ wrote on 2026-04-18, 22:45:

jami3rez wrote on 2026-04-18, 21:01:

I’ve actually been able to put a 10gb HDD on and it detects 2gb of useable space which it has formatted and I have installed MS […]
Show full quote

I’ve actually been able to put a 10gb HDD on and it detects 2gb of useable space which it has formatted and I have installed MS DOS on it.

I’m not bothered about being able to use more, 2gb is fine by me.

I’m just confused why the other, smaller drives couldn’t use 2gb of their space and in the BIOS only saw 93mb and 487mb respectively?

I’m definitely interested in a BIOS update if that will smooth things over.

Jan explained what is happening in the post above yours, the BIOS has a faulty display routine that resets when the size count goes over 2015MB. In the case of a 10GB drive, the capacity is limited to 8GB by the BIOS (usually about 8033MB) and the counter reset at 2016MB, 4032MB, 6048MB and the counter would finally rest on 1985MB giving the appearance of a ~2GB drive.

Accoring to Jan this is just a visual error and the drives that show up as 93~487MB should still format to their full capacity (subject to OS limits)

I see, sorry I think I misunderstood. I’ll have a look at this later.

I’d been working on this build for about 7 hours yesterday, my brain was a bit fried! I’ve never had anything earlier than Win 98, there are so many quirks to learn. I do appreciate the input from people like you guys.

In this case the best is just let the bios detect whatever can do, and use a overlay like ezdrive

Anyway if possible better to use a fix data like 993,16,63

@NeoG_ and @DaveDDS,
Thanks for clarifying my explanation. 😀

@jami3rez,
So, due to the Harddisk size display rollover to zero at each 2016MB, the BIOS is actually telling you that it detected the 2.6GB drive as 2016+487=2503MB. You should see the same figure in Fdisk when you partition this drive.
The same goes for the 4.3GB drive that shows at 93MB. Here the BIOS has detected this drive as 2016+2016+93=4125MB.

You can just leave it at that and use the full capacity of these drives, while disregarding the size that the BIOS displays.
Back in the day, this is what I did with my SY-030F2 board which had a 1994 Award BIOS with the same 2GB Harddisk display limit bug. Years later, when I found a way to fix this bug, I finally updated this board’s BIOS. Actually, this is how my BIOS patching hobby started. 😉

The use of Drive overlay software like EZ-Drive, as theelf suggested, is another solution. But because your BIOS already has native support for up to 8GB drives, EZ-Drive is only needed if you want to use the full capacity of >8GB drives.
However, remember that DOS 5/6.x is limited to 8GB drives. So when using larger drives, you have to use at least Windows 95 and its underlying DOS 7.

The fixed SY-025JKL_J1 BIOS I mentioned before can be downloaded from this thread:
Re: Fixing up an broken 486 I got from a local radio.
Your original 64KB 28-pin DIP BIOS chip is probably a 27C512 or equivalent UV-EPROM. These chips need to be erased by UV-light, hence the quarts window on top, before you can re program them.
So it is much easier to buy a new (E)EPROM to program the updated BIOS and keep the original EPROM as backup.
For these 486 BIOS updates I advise to use a Winbond W27C512 EEPROM. These are compatible with 27C512 UV-EPROMs but can be electrically erased for re-programming. No hassle with UV-light anymore.
But you still need an EEPROM programmer to program the new BIOS in the EEPROM chip.

Cheers, Jan