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19

The physical geometry how many heads the drive actually has is not the same as the logical geometry of how many heads is presented to the PC by the drive. By translating the geometry, the drive can be fully addressable to up to the maximum of approximately 8 gigabytes in CHS mode, as the IDE interface is limited in CHS mode to 16 heads, 63 sectors and 16383 ...


13

In all the BIOS setups I was dealing with that have similarly 47 drives to chose from the first or the last one was editable directly in BIOS SETUP for manual settings. Sometimes the manual settings was done in different menu entry (near formatting utility ... but beware do not accidentally format IDE !!!). IIRC DOS uses BIOS routines for HDD access so if ...


12

As far as I can tell, the first edition of the IBM 5150 Technical Reference is the only IBM manual which mentions 45 cylinders. Few Technical References document the FDC, which is where the “45 cylinder” mention appears, but those that do, other than the 5150 first edition, don’t reproduce this — see for example the first edition of the IBM 5160 Technical ...


12

It can be done using a third-party "disk manager", such as OnTrack Disk Manager and EZ-Drive. At the end of the DOS era, these came bundled with many hard disks. https://en.wikipedia.org/wiki/Logical_block_addressing#Enhanced_BIOS Some downloads. Kroll OnTrack have allowed this to be shared freely! https://www.philscomputerlab.com/ontrack-disk-manager.html ...


10

Modern hard drives are not addressed by Cylinder, Head and Sector (CHS) coordinates, but by Linear Block Address (LBA). This is mostly due to the number of sectors per track changing across the width of the disk, as more sectors can be squeezed into the larger circles described by the outer tracks than the inner ones. The drive electronics automatically ...


10

QEMU is not at fault here. The discrepancy comes from the BIOS. When I create a disk image as described in the question, then attach it to a QEMU virtual machine and use the info qtree command in the monitor, this is the geometry I see reported: cyls = 248 (0xf8) heads = 16 (0x10) secs = 63 (0x3f) The same geometry is ...


9

The problem is in the geometry. Not in the physical disk geometry, but rather in the translation how the BIOS must translate the geometry for DOS when using disks larger than 1024 cylinders. The laptop, or very close model of it, was sold with an 800 MB drive, so we have to assume that the laptop properly supports disks larger than 504 MiB, i.e. disks with ...


8

Very briefly: The way harddisks are addressed changed over time. Originally, you'd specify cylinder/head/sector (CHS), then it switched to logical block addresses (LBA), and the commands for those went through various versions with an increasing number of bits. As you can read on Wikipedia, LBA first used 22 bits, then 28, then 48. So you need to distinguish ...


6

Whew, I've got it solved! I took one of the disk images with Windows 95 installed on it, and examined it with a hex editor. I noticed that when the Windows installer program initially sets up the system files on the C: drive, it puts IO.SYS rather "far" into the filesystem, actually more than 100 MB inward. What I tried then was to perform a clean ...


5

That BIOS screen clearly says that it detects the drive as roughly 8 GB. The parameters say 16383/16/63 as so this BIOS cannot detect or provide the extended disk services that would allow the drive to be used beyond the 16383 cylinders, or the 8GB limit. It does not matter if another program can detect the size properly by communicating with the drive ...


5

Floppy disk drives could usually mechanically access more than 40 tracks, but only 40 were actually used, "formatted". First track is on the outer edge of the disk, there is a detector than signals when the disk head has reached the edge. Other tracks are reached by moving by a known number of phases a stepping motor. Simple drives use "CAV&...


4

Some older computers used to identify 512-byte sectors by specifying a combination of a head number, sector number, and cylinder number. For historical reasons, the head number was often limited to the range 0-15, sector number 1-63, and cylinder number 0-1022. This limited disks to 8,455,200,768 bytes--a little bit under 8 GiB. Newer drives simply access ...


4

Because these drives have different geometries and multiple partitions, you can't dd the whole thing in one pass and expect everything to work. In particular, your DOS partitition which was located at cylinder 9, track/head 0, sector 1 on the old drive, is now located somewhere different on the new drive (which has 4 times as many tracks per cylinder as the ...


2

Like Ken Gober said, you can't expect to clone drives with different geometries this easily :) Also you should make sure the BIOS recognizes the drive properly. If it's an early revision it might be limited by the 504 MB barrier (1024/16/63). Your 1GB CF exceeds those (967/32/63). If in doubt you can use the latest BIOS (sp1992) which allows for drives up ...


1

This is a logical–physical geometry mismatch. Like @Justme’s answer explains, the ‘logical’ geometry used by the BIOS disk interrupt services, and the ‘physical’ geometry reported by the disk controller are not necessarily the same. This is because the BIOS interrupt call interface and the hardware interface of the ATA controller establish different limits ...


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