24 Aug
2012
24 Aug
'12
5:48 p.m.
On 08/24/2012 07:35 PM, Chuck Guzis wrote:
But even more problematic than that, "F_CLOSE" is a BDOS call, not a
BIOS call, and the BIOS doesn't know when a file is being closed. (IIRC)
So one wouldn't be able to do this in the BIOS, it would require a
modification to the BDOS.
Simple, Most
of the systems ran without interrupts and did zero
timekeeping so
while the ap was running it was in control, when the ap returned
control CPM was not keeping time either. In essence there was no
"idle time" as that concept is only known to multitasking or forground
background systems that used blocked IO and task lists to manage what
the CPU was doing( rather than spinning in loops).
Easy, move the heads when a close is issued. Yes, I know that many
programs didn't bother with open or close calls, as CP/M cared only
that the FCB described something, whatever it was. Move the heads
when the system is sitting at a command prompt. Moving one cylinder
is trivial in terms of timing compared to the average rotational
latency of a disk.
One could do this with an idle timer in the BIOS keyed on console I/O.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA