[Coco] Re: [Color Computer] Floppy contoler Q

[david_g21120]

--- In ColorComputer at yahoogroups.com, Phill Harvey-Smith 
<dragon at a...> wrote:
>
> Gene Heskett wrote:
> > On Saturday 14 January 2006 23:25, Phill Harvey-Smith wrote:
> >> This infers that this signal can also be used to select the 4th 
drive,
> >> however I'm unsure of the way this could be done.
> > 
> > Yes, however, this is assuming all 4 drives are single sided.  
Also the 
> > drive might have to be programmed for motor on on selection.
> 
> So if you have 1..3 drives then Side select is exactly that ? But 
if you 
> have 4 drives they have to be single sided ?
> 
> > It also required a jumper to be soldered onto the 4th drive to 
take it 
> > to a valid drive select signal on the drive with the other 3 
jumpers or 
> > switches set open.
> 
> Yeah that makes sense.
> 
> >> It may be possible 
> >> that the Tandy drives had some off board circuitry that 
somehowe did
> >> this (or a non standard cable), since I have never actually 
seen one,
> >> I do not know.
> > 
> > Their off board circuitry consisted of removing the connections 
from the 
> > card edge connectors and twisting the cable such that for the 
first 2 
> > drives, both were programmed to be (IIRC) drive 0 (unlike the pc 
drives 
> > that were all drive 1).
> 
> But the same idea none the less, I use a similar twist (pins 10 & 
12 
> IIRC), to undo the bodge and let me use 2xPC 1.44s (as 720) on my 
> CoCo/Dragon.
> 
> >			  It simplified things for the assemblers, 
but 
> > made life difficult for us, so we usually installed, or soldered 
the 
> > jumpers to assign the drive number on each drive, and then put 
fully 
> > populated connectors on the drive cable.
> 
> Yeah that figures, in other words we use things the way they where 
> designed, with a full cable and jumpers.
I have used 4 floppy drives with RDSOS in a RS and J/M controller 
with 4 drives on a CoCo3 without an issue all of the drives were 
used with the jumpers for drive select, two of them were the FD502 
DSDD floppy drives, under OS9(wich I use most of the time) I was 
accessing all of the drives as DSDD drives. The FD502 drives from 
Tandy/RadioShack had the correct jumpers on them. Under RSDOS the 
drives were 0, 1, 2, 3 accessed as SSDD. Under OS-
9 /d0, /d1, /d2, /d3 accessed as DSDD.
> 
> >> In case anyone wonders what I'm up to, I'm trying to port 
SuperDos (A
> >> Dragon dos enhancement), to use the RS-Dos hardware, as I 
figure this
> >> way an RS-Dos cartrage could be used with the Dragon (either the
> >> British one or the Tano).
> > 
> > I'd suspect that using the 1773 chip in a rsdos controller might 
require 
> > a software hack to superdos to compensate for the hard wired 
side 
> > select signal in the shack & clones controllers.
> 
> And difference in read/write sector commands, IIRC the 1773/1793 
encode 
> the sector sizes slightly differently, and this affects the exact 
format 
> of the command ($80 on rs, $88 on Dragon for read sec etc).
> 
> Yeah I have it disassembled, and am working on it that way with 
> conditional assembly I can build for Dragon, Dragon 
Alpha/Professional & 
>   hopefully RS-DOS. At the moment it seems to be reading sectors 
ok, 
> just from the wrong side of the disk !
> 
> Phill.
>







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