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Thread: Hard Drive with Old PC 386SX Clone and Phoenix Bios 1.10

  1. #11

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    Quote Originally Posted by Chuck(G) View Post
    If you can boot from a floppy, give IDESDI a shot--it should figure out the geometry, if the drive is functional.

    Attachment 56488
    Will give it a go and if this doesn't get me there, will move on to using a smaller CF card.

  2. #12

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    Quote Originally Posted by Heatvent View Post
    So when I boot from floppy, I am able to access the drive. I am just not able to boot from the CF.
    Sounds like it could be the geometry. Try Chuck's suggestion.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  3. #13

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    OK, so a multitude of things going on here. I fairly easily got the 128MB card to work. Although I was making the mistake of formatting it on the newer PC rather than the 386 PC so it was getting read errors. So only use a newer PC to boot into DOS and get the geometry of the drive. Then use the specs to setup the drive in the old PC BIOS. Then boot the old PC to dos and use FDISK to setup a partition and FORMAT to format the drive.

    I then proceeded to try the same method to setup a 1.6GB IDE 5.25" drive. When I went to format it was only 37MB! So I played around with the "Cylinders" setting in the BIOS. The 1.6 GB drive has 3148 cylinders, 16 heads, and 63 sectors. With these settings the drive was recognized at only 37MB by the PC. If I changed the cylinders to something above 1024 (2048 for example), the drive was recognized at 504MB. So I ended up changing "Cylinders" to 1024 and left the heads at 16 and sectors at 63 and it seemed to work/format. Not sure if this is the right way about it but it seems the BIOS does have a 504MB limit but allows larger drives to be setup but only up to a certain limit and then something goes sideways.

    If I understand this correctly (https://www.easeus.com/resource/cyli...ead-sector.htm) this is just all address where to store data. So by reducing the cylinders I am only letting the OS access the first 1024 tracks of the 3148 available on each platter. Since I know next to nothing about hard drives, let me know if this was an acceptable approach or if I am dooming my drive to certain failure (accelerated anyway ).

    Thanks!
    Last edited by Heatvent; October 5th, 2019 at 07:29 PM.

  4. #14
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    The 1024 cylinder limit is mostly an artifact of the BIOS software. For reading and writing on older BIOSes, the CX register is divided into 6 bits for sector number and 10 bits for cylinder. DL has the drive number (128...) and DH has the head number. Some BIOSes borrowed a couple of bits in the DH register for another couple of bits for the cylinder. Eventually that hit a brick wall, so the extended BIOS interface was implemented, which keeps the arguments in memory as a structure.

    So you'll have to limit the number of cylinders to 1024 or use a DDO to get around things.

  5. #15

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    Quote Originally Posted by Heatvent View Post
    So I ended up changing "Cylinders" to 1024 and left the heads at 16 and sectors at 63 and it seemed to work/format. Not sure if this is the right way about it but it seems the BIOS does have a 504MB limit but allows larger drives to be setup but only up to a certain limit and then something goes sideways.
    It looks like your BIOS truncates the disk as opposed to some of the other less desirable possibilities e.g., Wrap-Around, BIOS Ignorance and BIOS Failure. Truncation is more preferable than any of the other three possibilities.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  6. #16

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    Thanks for all the help and input on this. Glad I got this up and running. Maybe at some point I could try some of the other methods to use a different bios (network card?). However, I don't really see the point. I think I will be fine with 504MB of storage.

    So next step is to get the hard drive and CF card both working (I am waiting on a mountable CF card with bracket) so I can transfer files easily. Thanks again for the help!

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