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4GB disk in an old 486?

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First post, by cprieto

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I got a nice 486 mobo (OPTi 486WB Mainboard) with an AMI BIOS, this board comes without IDE or FDD controllers so I got a LCS-6624G Winbond ISA controller to connect a floppy disk drive and an SDD IDE card adapter with a 4GB SDD card. The BIOS is kind of old (I think around 1990-92) and I noticed it doesn't support LBA so I put the correct sec/heads/etc... in the BIOS and reported 3.8GB in size (3870 MB or something like that).

Once booted, MSDOS 6.22 fdisk reports the correct disk size (3.8GB) but it says the max disk size is 512MB (or something like that). Yes, I formatted the drive and as MSDOS told me, the disk size is now 512MB.

I had been reading this https://www.win.tue.nl/~aeb/linux/Large-Disk-4.html but I don't fully understand, what does set this size? the BIOS? the Winbond ISA controller for the disk? definitely not the OS (MSDOS 6.22 reports the card size correctly when the disk is LBA).

And just to confirm, I cannot do much to handle this 4GB card with this mobo? is that correct or there is any trickery out there to make it work?

Thanks a lot for your help, any information, reading or guidance about this would be highly appreciated!

Cheers!

Reply 2 of 4, by Horun

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Yeah Your BIOS probably has the 528MB HD size limit and no Large Disk support (Pre-LBA). Some explanations:
http://www.dewassoc.com/kbase/hard_drives/har … ze_barriers.htm

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 3 of 4, by DNSDies

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sounds like a BIOS limitation.
You may be able to find a hacked bios that removes that limitation, but more likely you'll either need to use a driver overlay software to get full access to the disk, or a bios that loads after the motherboard's bios and handles the IDE controller (like XT IDE)

Reply 4 of 4, by cprieto

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Thanks everybody, your answers has been pretty helpful, I was able to use OnTrack Disk Manager to handle a 2GB SD card without problems (I will be using FAT16 for my "experiments"). The only thing I am dealing with are problems related to using a 512MB CF adapter (it works fine with an SD to IDE adapter but fails with the CF adapter), I had read a similar thread in the forums and well, that is a separate problem.

Thanks for the links, I now understand more about DOS-BIOS and things like LBA and large disks.

Cheers!

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