Need to know the WD HD model number. Need to know the BIOS version of the Fic 486-GVT-2
The current bios does not support greater than 2GB HD and cannot properly ID the C/H/S.

The date of your motherboard bios would be handy too.

What version of Dos are you booting? Dos before win95 osr2 does not work woth cylinders > 1023

Here’s some notes that I typed up esrñier today
Re: 486 PC Hard Drive Troubles

Horun wrote on 2024-01-25, 03:43:

Need to know the WD HD model number. Need to know the BIOS version of the Fic 486-GVT-2
The current bios does not support greater than 2GB HD and cannot properly ID the C/H/S.

WD HD model number is AC14200-30RT

BIOS version is 4.50

Something that confuses me is that the failing 486 actually identifies C/H/S correctly (as shown on the drive, see picture), except for 2GB instead of 4 GB.
But in the working Pentium, C/H/S is identified as something else (1023/128/63), but is working anyway...

Bios older than July 1994 often let you enter larger values into the drive table, but internally the BIOS INT13 call rarely was able to process values larger than 1023 Cylinders , 16 Heads, 63 Sectors/Track, which is 512MB.

Your drive is 4 GB, so you likely need a BIOS INT handler newer than May 1996 to support that size.

Here are three common ways to do that:

• on a 486, there's a reasonably chance you can find an MR Bios v1.65 or newer that understands your 4GB drive if you enable cylinder translation. You would make a new EPROM and swap out the socketed chip on your motherboard.
• Make an option rom like XUB (xtide universal bios), put it on an isa add-in board and you get LBA28 and LBA48 support
• Set your drive to as smaller geometry, boot off floppy and install a drive overlay like Easy drive 9.09w and get LBA28 support.

douglar wrote on 2024-01-25, 11:14:

Bios older than July 1994 often let you enter larger values into the drive table, but internally the BIOS INT13 call rarely was […]
Show full quote

Bios older than July 1994 often let you enter larger values into the drive table, but internally the BIOS INT13 call rarely was able to process values larger than 1023 Cylinders , 16 Heads, 63 Sectors/Track, which is 512MB.

Your drive is 4 GB, so you likely need a BIOS INT handler newer than May 1996 to support that size.

Here are three common ways to do that:

• on a 486, there's a reasonably chance you can find an MR Bios v1.65 or newer that understands your 4GB drive if you enable cylinder translation. You would make a new EPROM and swap out the socketed chip on your motherboard.
• Make an option rom like XUB (xtide universal bios), put it on an isa add-in board and you get LBA28 and LBA48 support
• Set your drive to as smaller geometry, boot off floppy and install a drive overlay like Easy drive 9.09w and get LBA28 support.

Alright, many thanks for that detailed explanation!

d00mo wrote on 2024-01-25, 06:57:

WD HD model number is AC14200-30RT thumbnail_IMG_2673.jpg […]
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Horun wrote on 2024-01-25, 03:43:

Need to know the WD HD model number. Need to know the BIOS version of the Fic 486-GVT-2
The current bios does not support greater than 2GB HD and cannot properly ID the C/H/S.

WD HD model number is AC14200-30RT
thumbnail_IMG_2673.jpg

BIOS version is 4.50
thumbnail_IMG_2669.jpg

Something that confuses me is that the failing 486 actually identifies C/H/S correctly (as shown on the drive, see picture), except for 2GB instead of 4 GB.
But in the working Pentium, C/H/S is identified as something else (1023/128/63), but is working anyway...

Yes, that BIOS looks ugly.
It may have a border at 1 or 2 GB.
You probably may enter values below that border and use the disk with reduced size. Perhaps a DDO may help then... (3rd suggestion from doglar)

douglar wrote on 2024-01-25, 11:14:

Bios older than July 1994 often let you enter larger values into the drive table, but internally the BIOS INT13 call rarely was […]
Show full quote

Bios older than July 1994 often let you enter larger values into the drive table, but internally the BIOS INT13 call rarely was able to process values larger than 1023 Cylinders , 16 Heads, 63 Sectors/Track, which is 512MB.

Your drive is 4 GB, so you likely need a BIOS INT handler newer than May 1996 to support that size.

Here are three common ways to do that:

• on a 486, there's a reasonably chance you can find an MR Bios v1.65 or newer that understands your 4GB drive if you enable cylinder translation. You would make a new EPROM and swap out the socketed chip on your motherboard.
• Make an option rom like XUB (xtide universal bios), put it on an isa add-in board and you get LBA28 and LBA48 support
• Set your drive to as smaller geometry, boot off floppy and install a drive overlay like Easy drive 9.09w and get LBA28 support.

A follow up on this… I went ahead with the suggested option of using ez-drive and it works like a charm!
Down the road I used a CF card as well and both options now works perfectly!

My first retro build is now completed and it was extremely fun putting it together.
This site really is a wealth of information 🤗

Attaching a picture of the beauty 🤩

If you have an ISA network card installed, you can install the XTIDE Universal BIOS ROM chip on it, or make a standalone ISA 8bit mini card for it, except for the disadvantage that it will occupy an ISA slot, it is perfect.
I made a standalone card with a 64GB HDD on the 386 and 486, Everything was perfect.

zwrr wrote on 2024-02-20, 08:00:

If you have an ISA network card installed, you can install the XTIDE Universal BIOS ROM chip on it, or make a standalone ISA 8bit mini card for it, except for the disadvantage that it will occupy an ISA slot, it is perfect.
I made a standalone card with a 64GB HDD on the 386 and 486, Everything was perfect.

I read about it and would be fun to try out that road also!
Maybe next project… 😀