Replacing 8" drive with 3.5" drive on CP/M systems

From: Randy McLaughlin <>
Date: Sun Jan 30 19:01:39 2005

From: "Fred Cisin" <>
> On Sat, 29 Jan 2005, Randy McLaughlin wrote:
>> I have tried to get a quorum on comp.os.cpm but there are only a few with
>> any opinions.
>> We all agree that 3.5" drives are a viable way to go. Many prefer to
>> never
>> change from 8" drives.
>> I have a variety of CP/M systems with a variety of storage mediums.
>> The point is for those of us that use 3.5" HD drives should try and come
>> to
>> a consensus for a "standardized" format.
>> Questions such as sector size and numbering come to mind.
> Why not just stick with 8"?
> About 25 years ago, I asked Gary Kildall what the standard format was for
> 5.25" CP/M.
> He replied "eight inch single density".
> I said, "but what about machines with 5.25 inch drives? What is the
> standard format for them?"
> He replied "eight inch single density."
> If you are going to create a "new" CP/M format, then I would recommend
> using the same PHYSICAL specs as PC and Mac: 80 tracks per side, 2 sides,
> 18 sectors per track, 512 bytes per sector. That will simplify
> significantly the code needed to be able to write programs for
> transferring files back and forth.
> But the easiest ones to implement would be to match the format of their
> existing formats. 1.2M 5.25" drives were originally designed to be an
> almost drop-in replacement for 8" drives, with specs that look almost
> identical to the host machine. If you're intent on using 3.5" HD, then
> the easiest to implement (2 * 80 * 15 * 512) would waste a sizable amount
> of space, but who NEEDS more than that?
> --
> Grumpy Ol' Fred

One of the "standard" formats recommended by Teac is 2 * 80 * 18 * 512 for
3.5" HD which I personally lean toward. As I see it there are more storage
devices that use 512 byte sectors because of the great and all seeing OZ
(aka Willy boy).

The Imsai Series 2 SuperIO boots from Flash ROM but I have recommended to
Howard Harte to put an offset of two tracks so other systems can use
compatible formats.

I agree 8" SSSD is the only standard that exists for CP/M, I am only trying
to create a defacto-standard for systems coming into the 3.5" world. A
format of consensus if possible, I am beginning to doubt that a quorum of
interested people can be developed.

Received on Sun Jan 30 2005 - 19:01:39 GMT

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