23 Mar
2010
23 Mar
'10
7:44 p.m.
On Tue, 23 Mar 2010, Gene Buckle wrote:
How are you going to handle the data rate difference?
If memory serves,
using 1.44MB media results in a higher RPM and a higher data rate.
"720K" is 250K bits per second at 300 RPM ("DD diskettes)
(except for some old Sony drives (ask Tony) which ran at 500K/600RPM)
"1.4M" is 500K bits per second at 300 RPM ("HD" diskettes)
"2.8M" is 1000K bits per second at 300 RPM ("ED" diskettes
(barium-ferrite, vertical? recording))
SOME (NOT ALL) 5.25" drives switched back and forth between 300 and
360RPM, requiring 250K and 500K bits per second.
SOME (NOT ALL) 5.25" drives stayed at 300RPM, requiring 300K and 500K
bits per second.
The AT disk controller supported 250K, 300K, and 500K data transfer rates,
under software control -- THAT port and its code is the only part of
INT13h that isn't commented in the AT Technical Reference Manual.
--
Grumpy Ol' Fred cisin at xenosoft.com