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SkatKat adds:
I had a couple of these machines, and I had a program that ran in RS-DOS
that allowed 2MHz speed (ie. "high speed") disk drive access. In
OS-9 Level II, the drive speed as 2MHz. Also, In OS-9 Level II, I had also
used a 3.5" "80-track" disk drive in the old FD-502 drive
box.
The CoCo3 has since also been outfitted (by others) with Hitachi's 6309 and
63x09E (63C09E, etc.) CPUs and much more is STILL being done with those
CoCos by hackers who just wouldn't let go of the old machine. :)
More information about CoCo3 sound abilities by Darren Carter:
The CoCo3 featured a 1 bit DAC instead of a synth chip
and was only limited by how much CPU power you were willing and able to put
into audio. Generally that was 2-3 voices + drums. There was a dedicated
audio program called Lyra that could squeeze 8 instruments out
simultaneously without much trouble. There is a mod player for the CoCo3
that is pretty impressive. The CoCo3 could even do an admirable job of
sampling with very clear playback. There just wasn't a lot of CPU left.
The original CoCo-3 design featured the Orchestra-90 stereo synth board
integrated into the machine but Tandy scrapped that idea to milk profits.
The CoCo 3 with the synth board was less expensive to manufacture than the 2
had been. The GIME chip gave the CoCo3 some neat features such as hardware
scrolling and a 256 color mode in any resolution. Unfortunately for users,
Tandy never released documentation on these modes because they were
"buggy" (read: would blow Tandy 1000 out of water and they didnt
want that).
About the "GIME" chip, James Jones adds:
The CoCo 3 had a chip called the "GIME" chip
that handled both graphics and memory management. It didn't do bank
switching, but instead did actual memory mapping, mapping arbitrary 8K
pieces (rather large given the 6809's 64K address space) into what to
the 6809 looked like a contiguous space.
Under OS-9, each process had its own address space, though unlike the more
serious 6809 systems such as were made by GIMIX, the memory mapping didn't
have serious enforcement--if you only asked for 16K, the memory mapping
hardware still pointed somewhere for the other 48K, and wouldn't keep you
from getting to it.
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