Old PET/CBM documentation (was: "Quad-Density" disks)

From: Anders Carlsson (anders.carlsson_at_sfks.se)
Date: 2006-12-29 20:48:42

On Fri 2006-12-29 11:02, B Degnan wrote:

> I don't believe that CBM diskettes have the TPI printed on the labels.

I have the 8250 Test/Demo disk, and indeed it says "100TPI 2S" at the
end of the label. I also have the 8296 System Disk. It has a custom
label, but the underlying label is a Commodore one that says "100 tpi".

On my last PET-trip, I picked up four manuals. Would either of these
be particularly interesting to have in electronic format, either as
OCR:ed text/document or simply as images?

1. Commodore Business Computer User's Guide: Series 8000
Part number 320894. For the 16K and 32K models of the 8000.

It isn't overly technical and I couldn't find anything I didn't
already know.

2. Commodore Disk Reference Manual
No part number. For the D9090, D9060, 8250, 8050, 4040 and 2031.

It is a preliminary manual, printed on a typewriter or perhaps
stylewriter. It contains some technical data about the mentioned
drives and describes the disk storage formats (BAM etc). I suppose
a lot of the information is available elsewhere, but perhaps it is
useful to be made available online.

Quote from the manual:

> The model 8250 dual floppy disk unit uses a 100 Track per Inch (TPI)
> two headed drive with a formatted capacity of 1,066,496 bytes
> (characters) per drive. Each 8250 diskette has 154 tracks, 77 on each
> side, and is read/write compatible with the model 8050 disk drive.
> The 8250 uses Micropolis Tandon drives.
> The model 8050 dual floppy disk unit uses a 100 Track per Inch (TPI)
> single headed drive with a formatted capacity of 533,248 bytes
> per drive. Each 8050 diskette has 77 tracks, and is read/write
> compatible with the model 8250 disk drive. This compatibility is
> limited to one side of the diskette. The 8050 uses either Micropolis
> or Tandon drives.
> The model 4040 dual floppy disk unit uses 48 track per inch (TPI)
> single headed drives with formatted capacities of 174,848 bytes
> (characters) per drive. Each 4040 diskette has 35 tracks. The 4040
> is neither read nor write compatible with the model 8050 or the
> 8250 disk drives. Diskettes created on 4040 drives are read/write
> compatible with the model 2031 and the VIC-1540 disk units.

While clearly stating which type of *drive* the floppy disk units have,
I can't find a clear statement which type of *diskettes* is required. I
suppose more manufacturers used Micropolis and Tandon drive mechanisms,
and since they were so large, wouldn't all brands of floppies have been
labeled 100 tpi instead of 96 tpi if that makes a difference?

3. "Addendum to CBM Dual Drive Floppy Manual", part number 8250003.

It describes the 8250 in slightly different terms than the other
document, but I don't think it adds anything.

4. "Commodore 500/600/700 Series User's Guide", second edition (!).

It describes how to set up and use respective CBM-II series computer.
Part of the manual is already available on the Internet, but I
suppose the book as a whole would be valuable. Despite being the
second edition, the manual still fails to describe the video pinout
on the CBM 6XX (B128). It shows the video pinout for P500 and the
pinout of the internal monitor connector on the 7XX (high profile).
The latter is not so useful for an owner of a computer without a
built-in monitor. :-)

I thought the P500 was almost unheard of, even more rare than the
B500 model. Yet this guide in its second printing clearly describes
the P model (VIC-II, SID, two joystick ports), sometimes referred
to as Commodore 500. In one block diagram, it is even referred to
as Commodore 128, which I suppose relates to the B128.

Oh well, time to start scanning... :-)

Anders Carlsson

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