9 Nov
1999
9 Nov
'99
10:43 a.m.
Rumor has it that Fred Cisin (XenoSoft) may have mentioned these words:
On Tue, 9 Nov 1999, Roger Merchberger wrote:
Hmmmm... Looks like I need to grab the controller catalog # (and other
specifics) and keep it in my Palm...
P.S. To keep this on-topic, does anyone have
instructions on the hack to
convert the above-mentioned floppy controller to be able to handle 3.5" HD
floppy drives? I'd *love* to have a 1.44Meg floppy formatted under OS/9...
:-) Also, is there any way (without reconstructing the 6 million dollar
man...) to get two floppy controllers online using the MultiPak?
My recollection was that there were several different vartieties. Each
one will have slightly different issues. To add 3.5" HD floppies, you will need to provide
a different clock, way
to change it back and forth, and support for one more signal to the drive.
I know you need a different clock (500Khz signaling rate vs. 250Khz for
double-density) but I'd like to know if it's as simple as a DPDT switch &
another crystal, or are there more things to keep a lookout on (like
different buffers, software changes WRT timing issues, stuff like that...).
Why do you want to run more than one FDC? If it is to
run 4 instead of 2
drives, you can do that with minor hardware and software hacks to a
controller.
Well, IIRC the most drives you can hang off of one controller is 4 SSDD
drives, or 3 DSDD drives because the Side Select signal was used for one of
the drive select pins. (Again, I think... If I'm wrong, please enlighten
me.) I was looking to hang 3 DSDD & 3 DSHD drives off my CoCo... purely for
shits & giggles. If it's a ton of hardware work, "nevermind" comes to
mind.
However, if it's some hardware & hacking some device drivers, then... I've
always wanted to hack around with the device drivers of OS-9... :-)
Just musings of random tinkering... ;-)
Roger "Merch" Merchberger
--
Roger "Merch" Merchberger --- sysadmin, Iceberg Computers
Recycling is good, right??? Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
9 Nov
9 Nov
11:01 a.m.
On Tue, 9 Nov 1999, Roger Merchberger wrote:
They almost certainly all had the same RS
catalog # :-(. I'm not the
right person to ask. Better to check with somebody familiar with the
various RS variants, such as Dr. Marty <martygoodman(a)delphi.com>om>.
Rather than a switch, you'd probably want to control it in software, so as
to retain full low density DD capability. First step would be to find out
if others have been there before. If not, check with Allison about
whether the rest of the RS Coco FDC cartridge circuitry can properly
handle the higher speed.
That sounds about right to me.
My recollection
was that there were several different vartieties. Each
one will have slightly different issues.
Hmmmm... Looks like I need to grab the
controller catalog # (and other
specifics) and keep it in my Palm... To add
3.5" HD floppies, you will need to provide a different clock, way
to change it back and forth, and support for one more signal to the drive.
I know
you need a different clock (500Khz signaling rate vs. 250Khz for
double-density) but I'd like to know if it's as simple as a DPDT switch &
another crystal, or are there more things to keep a lookout on (like
different buffers, software changes WRT timing issues, stuff like that...). Why do you want
to run more than one FDC? If it is to run 4 instead of 2
drives, you can do that with minor hardware and software hacks to a
controller.
Well, IIRC the most drives you can hang off of one controller is 4 SSDD
drives, or 3 DSDD drives because the Side Select signal was used for one of
the drive select pins. (Again, I think... If I'm wrong, please enlighten
me.) I was looking to hang 3 DSDD & 3 DSHD drives off
my CoCo... purely for
shits & giggles. If it's a ton of hardware work, "nevermind" comes to
mind.
However, if it's some hardware & hacking some device drivers, then... I've
always wanted to hack around with the device drivers of OS-9... :-)
Easiest way would probably be to use one controller, and rig up a software
controlled switch to go between two cables. Otherwise, you run into
issues of whether the Coco used memory mapped IO, modifying second
controller to function at a different address, and writing new drivers.
Once you add the other clock circuitry, be sure to write a driver to do 8"
disks!
Somebody ELSE will probably know whether it has been done before.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
11:50 a.m.
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12:32 p.m.
Rumor has it that Tony Duell may have mentioned these words:
[2 FDCs]
Now this is where it gets interesting...
All I/O on the CoCo is memory mapped. It has to be -- the CoCo uses a
6809 CPU which doesn't have special I/O instructions.
Right. That confused me for a while when I started learning (unforch, I
only got as far as starting... :-( ) 80C85 code for my Tandy 200, with the
non-memory-mapped I/O capabilities...
Now, there are 2 chip select signals decoded on the
coco mainboard that
are brought out to the expansion connector. One enables the expansion
ROM (in a plug-in cartridge). The other is used to enable I/O devices in
the cartridge (IIRC, it's active from FF40-FF5F (or is it FF4F?)).
AFAIK, _all_ ROMs in cartridges are enabled by the first signal. Some
cartridges use the I/O select signal, others decode the address lines and
map their I/O devices elsewhere in the memory map. IIRC, the disk
controller is one of the few devices that uses this I/O select signal.
The multipak interface switches both the above select signals so that
they're only active on one slot at a time. It doesn't fiddle with any of
the address lines, though.
What this means is that many I/O devices (but not the disk controller)
are always accessible if plugged into a multipak, no matter which slot is
'selected'. But the disk controller is only accessible if the slot it's
plugged into is the active one. So in theory you can just plug in 2 disk
controllers and switch between then using the slot select register in the
multipack (I forget where this is -- FF7F????). Just don't ask me to
write the software.
I had forgotten about that tidbit... time to get out my spec's on the
Multipak and disk drivers again. Don't worry - I'm better with software
than hardware as that's where I started, so I can prolly write/modify
device drivers to handle that stuff... it's the hardware where I'm rusty.
Thanks... this weekend I might have to rustle up some books again, and
start plinking again... (or, get the Commie 128 I rescued up and running; I
have a Zork trilogy I want to play. ;-)
Glad to help improve the S/N ratio... ;-)
See ya,
Roger "Merch" Merchberger
--
Roger "Merch" Merchberger --- sysadmin, Iceberg Computers
Recycling is good, right??? Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
9176
days inactive
9176
days old
3 comments
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participants (3)
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ard＠p850ug1.demon.co.uk -
cisin＠xenosoft.com -
zmerch＠30below.com