16 Apr
2005
16 Apr
'05
11:37 a.m.
From: "Dave Dunfield" <dave04a at dunfield.com>
Sent: Saturday, April 16, 2005 10:45 AM
The 'T' command is not available in all versions of RDOS, RDOS v1 (used on
4FDC's) didn't support it and I'm not sure when it was added. The above
routine should work on all Cromemco FDC's. Cromemco's memory handling
evolved as time went on.
Randy
www.s100-manuals.com
Hi Randy,
<snip>
If you have 64K
of RAM RDOS can be copied to RAM giving you access to the
full 64K allowing Larger CDOS's: Using a random address such as 1000H:
ld hl,0C000H
ld de,2000H
ld bc,1000H
ldir
ld a,1
out (40H),a
ld hl,2000H
ld de,0C000H
ld bc,1000H
ldir
ret
Just use the substitute memory command to enter the above code (hex) and
do
a g 1000 (a return returns to RDOS). You are now running RDOS out of RAM.
You can have one 32K CDOS and maybe a 64K CDOS to transfer. BTW you never
have to use 8080 only opcodes since RDOS & CDOS only run on Z80's. Also
the
above code can go in any free space and is not address dependent.
I thought about doing this - in fact, you can use the 'T' command to cause
RDOS to copyitself to RAM ... but I would like to keep it running in 32k
as this is more easily achieved configuration in many cases.
I've put together a bit of documentation, and I have the transfer program
as well as CDOS and Cromix images ready to put up, however I'm having a
bit
of trouble with permissions on the server (which is remote to me)... I
hope I can get it resolved this weekend and get the files up.
Regards,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.parse.com/~ddunfield/museum/index.html