Half-Saint wrote on Yesterday, 10:44:

The difference between type 17 and stason is just landing zone 977 vs. nothing. I switched to using type 17.

It doesn't matter - MR535 uses voice-coil = auto-park.

I did as you guys suggested and managed to boot from a floppy into DOS. Was surprised to see that I can access C: fine. I don't know why the system won't boot. I tried running sys a: c: and despite DOS saying "System transferred", it still says "Non-system disk or disk error replace and strike any key when ready" at boot.

"SYS A: C:" only affects the C: partition.
There may still be some garbage in the MBR - you can try "FDISK /MBR", and make sure the partition is set Active.

I tried "fdisk /mbr" but that didn't help so I tried to format the hard drive via "format c: /s" but got an error "Invalid media or Track 0 bad - disk unusable".

So something is obviously wrong with the hard drive. Hopefully LLF will help.

Success! I low-level formatted the drive, ran FDISK from a DOS floppy, created a FAT32 partition, formatted the drive with /s parameter and was able to boot into DOS successfully afterwards 😀

Thanks to everyone that helped!

Run a scan disk and see if there are any bad sectors. But awesome work getting the drive working again.

Half-Saint wrote on Yesterday, 15:05:

created a FAT32 partition

I think it's FAT16.
Is it even possible to create FAT32 on such a small disk?

Anyway, now you can experiment a bit, and find the optimal interleave factor for that system...

chrismeyer6 wrote on Yesterday, 16:57:

Run a scan disk and see if there are any bad sectors.

First and foremost, during LLF, it's a good idea to enter the bad sectors listed on the sticker.

Some sectors were weak already at the factory, and they will cause random errors - even if tools like SCANDISK may sometimes fail to detect them.

Grzyb wrote on Yesterday, 18:27:

chrismeyer6 wrote on Yesterday, 16:57:

Run a scan disk and see if there are any bad sectors.

First and foremost, during LLF, it's a good idea to enter the bad sectors listed on the sticker.

Some sectors were weak already at the factory, and they will cause random errors - even if tools like SCANDISK may sometimes fail to detect them.

Yes, it's FAT32. FAT16 wouldn't let me create a partition bigger than 32MB.

BIOS LLF tool won't let me enter bad sectors, I can only mark the whole track which is a bit of a waste. I also found recommendations online NOT to mark bad sectors during LLF as they will show pu during FORMAT or SCANDISK will find them.

Anyway, according to the factory sticker there are two bad sectors.

Half-Saint wrote on Yesterday, 21:56:

Yes, it's FAT32. FAT16 wouldn't let me create a partition bigger than 32MB.

FAT16 supports up to 2 GB.
What DOS version are you using?

Half-Saint wrote on Yesterday, 21:56:

Yes, it's FAT32. FAT16 wouldn't let me create a partition bigger than 32MB.

No, it's not FAT32. FAT32 is FAT with 32-bit cluster numbers, a format introduced with an OEM service release of Windows 95.

You are using FAT16 with 32-bit sector numbers. This is partition type 6 (called "BIGDOS" by the classic Norton Utilities). This type has been introduced with the enhanced Compaq OEM version of MS-DOS 3.3 called Compaq MS-DOS 3.31, and also exists in vanilla MS-DOS since MS-DOS 4.0. There is no need to use 32-bit cluster numbers on your partition, as the CHKDSK output clearly shows that you only have around 20.000 clusters, which perfectly fits into 16 bits.

mkarcher wrote on Yesterday, 22:07:

Half-Saint wrote on Yesterday, 21:56:

Yes, it's FAT32. FAT16 wouldn't let me create a partition bigger than 32MB.

No, it's not FAT32. FAT32 is FAT with 32-bit cluster numbers, a format introduced with an OEM service release of Windows 95.

You are using FAT16 with 32-bit sector numbers. This is partition type 6 (called "BIGDOS" by the classic Norton Utilities). This type has been introduced with the enhanced Compaq OEM version of MS-DOS 3.3 called Compaq MS-DOS 3.31, and also exists in vanilla MS-DOS since MS-DOS 4.0. There is no need to use 32-bit cluster numbers on your partition, as the CHKDSK output clearly shows that you only have around 20.000 clusters, which perfectly fits into 16 bits.

Pardon my ignorance, haven't had to deal with FAT16 for about 30 years. I should have worded my reply differently - I remember not being able to make bigger partitions in DOS 3.3 that my parents PC used back in the 80s (I know DOS version because I still have those 5,25" boot disks somewhere). All I had at hand was one DOS 6.22 boot disk so I used its FDISK utility to partition the HDD etc.

Half-Saint wrote on Yesterday, 22:25:

Pardon my ignorance, haven't had to deal with FAT16 for about 30 years. I should have worded my reply differently - I remember not being able to make bigger partitions in DOS 3.3 that my parents PC used back in the 80s (I know DOS version because I still have those 5,25" boot disks somewhere). All I had at hand was one DOS 6.22 boot disk so I used its FDISK utility to partition the HDD etc.

This makes perfect sense. There are two variants of FAT16 partitions: FAT16 with 16-bit sector numbers, which are supported since MS-DOS 3.0, and FAT16 with 32-bit sector numbers, is supported in MS-DOS 3.31, but not yet in DOS 3.3. Actually, there is absolutely no difference in how the FAT16 file system works, but MS-DOS 3.3 does not support partition sizes above 32MB at all (becuase that's the maximum size you can address with 16-bit sector numbers in a partition, and DOS 3.3 internally uses 16-bit numbers to identify sectors in a partition), so MS-DOS 3.31 introduced a new partition type for bigger partitions to prevent MS-DOS 3.3 to damage partitions that are too big to be handled by that system.

EDIT: Removed the wrong claim that FAT16 was introduced at the same time as hard disk support.

mkarcher wrote on Yesterday, 22:49:

This makes perfect sense. There are two variants of FAT16 partitions: FAT16 with 16-bit sector numbers, which are supported since MS-DOS support hard drives, that is MS-DOS 2.0, and FAT16 with 32-bit sector numbers, is supported in MS-DOS 3.31, but not yet in DOS 3.3. Actually, there is absolutely no difference in how the FAT16 file system works, but MS-DOS 3.3 does not support partition sizes above 32MB at all (becuase that's the maximum size you can address with 16-bit sector numbers in a partition, and DOS 3.3 internally uses 16-bit numbers to identify sectors in a partition), so MS-DOS 3.31 introduced a new partition type for bigger partitions to prevent MS-DOS 3.3 to damage partitions that are too big to be handled by that system.

FAT uses cluster id, not sector id, right ?

mkarcher wrote on Yesterday, 22:49:

FAT16 with 16-bit sector numbers, which are supported since MS-DOS support hard drives, that is MS-DOS 2.0

FAT16 was introduced in DOS 3.0.
DOS 2.x only supports FAT12, for both floppies and HDDs.

See also: DOS 3.00-3.30 limits, with a riddle

weedeewee wrote on Yesterday, 22:59:

mkarcher wrote on Yesterday, 22:49:

This makes perfect sense. There are two variants of FAT16 partitions: FAT16 with 16-bit sector numbers, which are supported since MS-DOS support hard drives, that is MS-DOS 2.0, and FAT16 with 32-bit sector numbers, is supported in MS-DOS 3.31, but not yet in DOS 3.3. Actually, there is absolutely no difference in how the FAT16 file system works, but MS-DOS 3.3 does not support partition sizes above 32MB at all (becuase that's the maximum size you can address with 16-bit sector numbers in a partition, and DOS 3.3 internally uses 16-bit numbers to identify sectors in a partition), so MS-DOS 3.31 introduced a new partition type for bigger partitions to prevent MS-DOS 3.3 to damage partitions that are too big to be handled by that system.

FAT uses cluster id, not sector id, right ?

It's true that the FAT filesystem internally uses cluster numbers for managing its data. But the FAT filesystem driver reads and writes sectors by passing sector numbers to the partition driver (INT 25/INT 26), and this interface is limited to 16-bit sector numbers in MS-DOS before 3.31.

mkarcher wrote on Yesterday, 23:11:

weedeewee wrote on Yesterday, 22:59:

mkarcher wrote on Yesterday, 22:49:

This makes perfect sense. There are two variants of FAT16 partitions: FAT16 with 16-bit sector numbers, which are supported since MS-DOS support hard drives, that is MS-DOS 2.0, and FAT16 with 32-bit sector numbers, is supported in MS-DOS 3.31, but not yet in DOS 3.3. Actually, there is absolutely no difference in how the FAT16 file system works, but MS-DOS 3.3 does not support partition sizes above 32MB at all (becuase that's the maximum size you can address with 16-bit sector numbers in a partition, and DOS 3.3 internally uses 16-bit numbers to identify sectors in a partition), so MS-DOS 3.31 introduced a new partition type for bigger partitions to prevent MS-DOS 3.3 to damage partitions that are too big to be handled by that system.

FAT uses cluster id, not sector id, right ?

It's true that the FAT filesystem internally uses cluster numbers for managing its data. But the FAT filesystem driver reads and writes sectors by passing sector numbers to the partition driver (INT 25/INT 26), and this interface is limited to 16-bit sector numbers in MS-DOS before 3.31.

So is the on-disk format exactly the same, and the new partition type is to just to stop truncation of sector numbers on pre-DOS 3.31 attempting to access it, from massively corrupting the filesystem?

jakethompson1 wrote on Yesterday, 23:15:

So is the on-disk format exactly the same, and the new partition type is to just to stop truncation of sector numbers on pre-DOS 3.31 attempting to access it, from massively corrupting the filesystem?

Nearly the same. I omitted one detail for brevety. The classic FAT parameter block, which is part of the boot sector, includes a field called "total sector count", which is a 16-bit field. If a FAT paratition contains more than 65535 sectors, this field is zero, indicating that a new field (at an offset that was previously not part of the parameter block) contains a 32-bit sector count. Apart from the different field for the sector count, the on-disk format is exactly the same.

Well, if I can't mark individual sectors, what do I do? Is there some other software I can use?