Using 3.5" HD drives on CP/M systems

[Randy McLaughlin]

From: "Vintage Computer Festival" <vcf at siconic.com>
Sent: Sunday, February 06, 2005 12:21 PM
> Here's a suggestion...
>
> The Epson PX-8 had 3.5" drives available as an add-on.  The PX-8 was of
> course a CP/M machine.  Why don't you start by investigating what Epson
> did?
>
> Sellam Ismail                                        Vintage Computer 
> Festival
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This is an example of missing the primary assumption:

The 3.5" drives used on most CP/M systems are driven at 250K MFM.

3.5" DD (125K FM, 250K MFM) are simple extensions of 5.25" 48tpi drives.

I am concerned about 3.5" HD (250K FM, 500K MFM).  This environment has the 
same transfer rate as standard 8" drives but it uses a different rotational 
speed.  This means that you can not simply extend an existing format.

One other point that keeps coming up is using 3.5" DD exclusively.  Many 
systems can not handle this data rate other systems would require hardware 
modifications, another point is the storage would be 1/2 of HD.


For systems running 250K FM (8" single density) would normally use 26 
sectors at 360 RPM, 32 sectors at 300RPM.  This is the issue, given that new 
formats are required.  The question is can enough people agree what formats 
are appropriate?

To me 250K FM would obviously be best to use 32 128 byte sectors even though 
going by Teacs FD235HF manual you can use 18 256 byte sectors or 10 512 byte 
sectors.  This is the closest to the 8" SSSD standard available.



Randy
www.s100-manuals.com