floppy controller IC (was Re: Fixing a PET?)

From: Roger Merchberger <zmerch_at_30below.com>
Date: Tue Sep 28 21:51:43 1999

Rumor has it that Glenatacme_at_aol.com may have mentioned these words:

>Thanks again! This is valuable information for me. I've got bins full of
>half-height 5.25" drives here, so if worse came to worse and I had to
>the 1770 with a 1772 I'm certain I could come up with a compatible drive.

I've found that in most cases, if the drive is double-sided & 40 tracks, it
will support the 6ms step rate (correct me if I'm wrong...), tho anything
less (single sided, or 35 tracks) I have no clue about. I do know that the
double-sided 40 track drive that came with my FD-502 Tandy Color Computer
floppy setup did support 6ms without any problems.

>Interestingly, with this system when a disk is formatted it is required that
>the number of TPI be input. This is then stored on the disk so I might have
>one 5.25 DSDD disk with 40 TPI, and another with 50. The maker of the
>says that it will support drives up to 255 tracks per side, "if the drives
>themselves ever do."

Now, do you mean Tracks, or Tracks per Inch? TPI is the density of the
tracks themselves, with 35/40 track 5.25 inch drives usually used 48TPI.
80-track 5.25 inchers (720K & 1.2M) used 96TPI, and all 3.5" drives that I
know of are 135TPI. I don't recall what TPI the old 2" drives in the Zenith
MinisPort were, but I think it was around 200tpi or so -- they were 80
track DSDD 720K drives.

Roger "Merch" Merchberger   ---   sysadmin, Iceberg Computers
Recycling is good, right???  Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
Received on Tue Sep 28 1999 - 21:51:43 BST

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