On Sat, 17 Jun 2023, Steve Lewis via cctalk wrote:
I finally got an IBM 5120 earlier this month, to complement the 5100 and
5110 that I already have.
. . .
My only question is: how "universal" are 8" disk? This 5120 only came with
a single IBM 8" Diagnostics disk. It looks to be in fine condition, but
I've no idea about the data.
So far I haven't been able to read it - it's probably more hardware/drive
issues, I'm still investigating. But I'm wondering if I had other 8"
disks (3M SS/SD), should I be able to format/MARK them?
I've used old tape decks and 5.25" drives - but 8" drives is all new
territory for me.
I do not know anything about 5120.
But, several sources mention the drives as being 1.2M
That would be double sided, double density.
Are you sure that you want SS/SD?
One article mentioned 256 bytes per sector, which would be consistent with
double density, as single density 8" was usually 128 bytes per sector.
You can usually get away with formatting a SD (FM) disk as DD (MFM), but
SS and DS 8 inch are different!
A few quick things about 8", (which you are likely to already know)
1) write protect is opposite of the way 5.25" does it; an open notch is
write protected, you need to cover the write protect notch if you want to
write.
2) single sided and double sided 8" disks have the index hole in the
jacket in different places. Therefore, they are not fully
interchangeable.
single sided disks will often have a "1" on them; double sided sometimes
have a "2"
"1D" and "2D" are single and double sided, double density.
Some drives have two sets of index sensors, to be able to handle both
single and double sided; some do not.
Punching additional holes in the jacket does work to convert one to the
other, which ends up looking a lot like the index holes for the
hard-sectored disks.
http://www.bitsavers.org/pdf/3M/3M_Diskette_Reference_Manual_May83.pdf
figure 3 shows the locations of the index holes
With a SS and a DS side by side, it's obvious; if you don't have both, . . .
If you imagine a line along the read/write slot, and a line from the
center of the hub hole, the SS is at a 7 degree angle, and the DS is at a
26 degree angle
--
Grumpy Ol' Fred [email protected]
