[Coco] hard disk performance

[Chuck Youse]

So, quick question, folks - does anyone have any basic performance data
for hard disks on 6809 NitrOS-9 Level II systems?  I only ask out of
curiosity; I've tweaked my HDISK driver to get probably fairly close to
maximum performance out of it (without being rude to the rest of the
system by disabling interrupts or doing any busy-waiting) and megaread
reports about 45K/sec transfers.  As far as usability goes, it seems
pretty peppy - and given that it's written to be nice to a multi-tasking
system, heavy disk I/O doesn't impact the rest of the system much
(interactive processes remain beautifully responsive).

I vaguely recall seeing numbers from megaread in the 70-80K range
(reported by others), and I'm wondering how much of this is just a
limitation of my hardware design, how much is due to the fact that I'm
running on a stock 6809 Coco 3 vs a 6309-enhanced one.

Any info out there?

I have to say; back when I was a poor kid with a 128K Coco 3 and a pair
of single-sided drives and a black/white TV, I loved the OS-9.  The
addition of a hard disk makes the system a thousand times more useful.
What a beautiful thing.

C.

[For those who are curious, some of the 'limitations of the design' I
refer to above include not being interrupt-driven and having to diddle
with MPI.Slct to map the hardware registers into FF40-FF4F, which
necessitates quite a few cycles to read/write a register.  During the
PIO transfers I try to group the transfers into 8s to minimize the
overhead and simultaneously allow timely servicing of system
interrupts.]