bear
Veteran Member
Ladies, gentlemen:
I am attempting to track down the cause of a problem accessing an MFM hard disk in an IBM 5170 AT. This disk has some data on it that I would like access to (copies of files from another drive with a failing format, prior to having run spinrite on the failing drive). It doesn't exactly matter, but the drive is a Miniscribe 3650 (40 MB). I left myself a post-it on top of the drive indicating I had formatted it as a type 20 (30 MB), leaving one head and some cylinders unused.
Indeed, the drive passes the seek and read tests in the IBM AT Diagnostics, with it set as type 20. There are a couple of sectors the read test fails which weren't originally flagged as defective during the format, but they are all beyond cylinder 250 and nowhere near track 0. This suggests to me the drive is formatted appropriately for the controller and is basically functioning correctly.
But DOS doesn't recognize it. FDISK says "Error: unable to access drive 2" when I pick option 5 to select that disk, so it's pretty clear DOS is deeply unhappy about something on the disk. If it had a partition >32 GB or some other OS partition on it (which it wouldn't) or even no partition table at all, I'd still expect FDISK to at least be able to select the drive.
This may be relevant: when DOS boots, something very very early in the boot process causes that drive to seek every track in order. Is DOS reading something off the drive that it finds nonsensical (one possible idea: a track or head outside the parameters of what should be available according to the drive type, which might indicate my note is inaccurate or misleading somehow - it's possible I had it on the WD1002 controller, but in some other machine with a different set of parameters for "type 20") and this is what it's unhappy about? How can I prove if this is the case?
Is there a way to dump raw sectors off the drive, so I can get an idea of what might be going wrong?
Any advice welcome.
I am attempting to track down the cause of a problem accessing an MFM hard disk in an IBM 5170 AT. This disk has some data on it that I would like access to (copies of files from another drive with a failing format, prior to having run spinrite on the failing drive). It doesn't exactly matter, but the drive is a Miniscribe 3650 (40 MB). I left myself a post-it on top of the drive indicating I had formatted it as a type 20 (30 MB), leaving one head and some cylinders unused.
Indeed, the drive passes the seek and read tests in the IBM AT Diagnostics, with it set as type 20. There are a couple of sectors the read test fails which weren't originally flagged as defective during the format, but they are all beyond cylinder 250 and nowhere near track 0. This suggests to me the drive is formatted appropriately for the controller and is basically functioning correctly.
But DOS doesn't recognize it. FDISK says "Error: unable to access drive 2" when I pick option 5 to select that disk, so it's pretty clear DOS is deeply unhappy about something on the disk. If it had a partition >32 GB or some other OS partition on it (which it wouldn't) or even no partition table at all, I'd still expect FDISK to at least be able to select the drive.
This may be relevant: when DOS boots, something very very early in the boot process causes that drive to seek every track in order. Is DOS reading something off the drive that it finds nonsensical (one possible idea: a track or head outside the parameters of what should be available according to the drive type, which might indicate my note is inaccurate or misleading somehow - it's possible I had it on the WD1002 controller, but in some other machine with a different set of parameters for "type 20") and this is what it's unhappy about? How can I prove if this is the case?
Is there a way to dump raw sectors off the drive, so I can get an idea of what might be going wrong?
Any advice welcome.