giles@ucf-cs.UUCP (Bruce Giles) (04/13/84)
I'm not totally lost around either hardware or software, and bought my
CoCo for experimentation anyway (shades of Dr. Frankenstein...:-) so,
IS THERE ANY STRONG REASON FOR ME TO BUY A RS FIRST DISK?
I have been considering constucting an extra board for the CoCo with:
(1): a dsdd disk controller, with separate data separator,
(so I can use a couple 80 tk double-sided disks)
(2): *real* serial port and parallel ports, with a spool on the
serial port,
(3): a decent video generator chip (24x80) to feed a monitor,
(possibly looking like a serial terminal so as to free the
coco's main memory, but still allowing the graphics):
(4): a real-time clock,
(5): possibily a new keyboard decoded,
(6): possibily a modem hard-wired independently of the above
serial port.
Finally, after talking to someone else at UCF with a CoCo, I have also
seriously been considering throwing in a second 6809 to control all
of this equipment. The CoCo's cpu would do the 'real' work, while
the second cpu would be a I/O processor, acting like a virtual disk
(i.e., cpu1 sends data to cpu2 and immediately considers it written
to disk, when cpu1 requests something from the disk, several sectors
are read and stored in RAM for subsequent requests).
I've been told that the advantages of such an arrangement would be
spectacular, but I still haven't been fully convinced -- will the
effort required to totally replace the RS disk controlling software,
and make the necessary patches to OS-9 afterward, be worth my time?
Especially considering that I must write the software for all of this
in assembler until I get OS-9 working, at which point I will almost
undoubtably rewrite the entire thing in C?
ave discordia going bump in the night ...
bruce giles
decvax!ucf-cs!giles university of central florida
giles.ucf-cs@Rand-Relay orlando, florida 32816sdyer@bbncca.ARPA (Steve Dyer) (04/13/84)
It is certainly advisable to avoid buying a R/S disk, even as your first (I
didn't take this advise, and only recently sold it off to a true RSDOS
fan.) It will run no faster than a 20 ms step rate, has only 35 tracks, and
is single-sided. I would advise buying two double-sided TEAC or Shugart
40 track drives--these will read and write ordinary R/S disks. On the other
hand, it is probably a good idea to buy the Radio Shack disk controller (or
the functionally compatible J&M controller), simply because you will be
able to run the R/S "standard" OS9 operating system. I recommend two
disks because attempting to use OS9 with only one disk is an exercise
in patience, if not futility, and the new K&R C compiler practically
demands two disk drives.
The R/S controller can support double sided disks, provided you don't use
their 34-pin ribbon cable which uses the "side select" pin as drive 3
select, and which addresses drives at the connector. What you want is a
cable which passes all pins straight through to the drives. Thus, the R/S
disk controller, suitable programmed, can support three double-sided
drives, 40 or 80 track. FHL Flex, and several OS9 disk driver replacements
use this scheme.
Now, if you are interested in performance, the RS controller stinks
(as do many inexpensive non-DMA controllers.) The controller asserts
HALT to the 6809 during the period that it cannot accept or produce
a byte of data, and disk reads and writes run in a tight lock-step
loop. But, having this controller will allow you to develop a better
hardware scheme.
--
/Steve Dyer
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