21 May
2013
21 May
'13
3:19 p.m.
> wondering... would it be viable to build a
version that supported
> 1.4MB "HD" drives? I realise this would mean a different FDC chip, but
> are there other implications apart from tweaking the DOS?
On Tue, 21 May 2013, Tony Duell wrote:
Most older 3.5" HD drives support 720K disks.
Unlike the 5.25" IBM PC
drives, the spindle speed on the 3.5" ones, and the number of cylinders,
is the same for DD and HD drives (yes, Frid, I am misusing those terms a
bit, but I think you know what I am talking about).
Sometimes it's just more practical for conveying the idea. Such as
referring to "360K" disks and drives V "1.2M" disks and drives, etc..
Sometimes it's just futile to tilt at that mill. ("1.44M", 65.535K,
1024000 byte "MB", "DB9", etc.)
However, I worry that use of "HD" V "DD", particularly in the context
of
thinking that that will require a different FDC chip MIGHT be due to a
marketing inspired misunderstanding and mistaken assumption that HD is
different from DD without realization that it IS DD at a higher speed.
In most cases the FDC chip can remain the same, what
it needs is a higher
data rate, A faster write clock and a modification to the dat separator
clock. If the FDC is campable of handlign 8" drives, then it can handle
HD 3.5" drives.
Minor nit: That should be clarified/limited as 8" DD
(Machines that handle only 8" SSSD would not be capable)
--
Grumpy Ol' Fred cisin at xenosoft.com