28 Mar
2000
28 Mar
'00
12:39 p.m.
On Tue, Mar 28, 2000 at 07:51:51PM +0100, Tony Duell wrote:
Actually, whether it changes the drive speed is often
a
jumper-configurable option as well. And most PC drives are jumpered so
that the drive speed is NOT changed -- PC 1.2Mbyte drives run at 360rpm
even when used with DD disks (but the controller data rate is increased
from 250kbps to 300kbps to compensate).
The nice thing about this feature is that once the jumpers are set, it's
the FDC+FDD's business and software doesn't have to know which way it's
set up. Writing 01h to 3F7h sets the drive for either 250kHz/300 RPM
or 300kHz/360RPM, whichever is appropriate for this FDC+FDD combination.
Either way you can access 360 KB disks, kinda, and RX50 disks, definitely.
John Wilson
D Bit