[Coco] Re: double disk drive

[Robert Emery]

> Yes, I want a switch to use either drive as drive 0 at any time.
> 
> I try Crystal City on drive 1 yesterday but it don't works. 
> Crystal City works only on drive 0 (I think).
> 
> I see on the Bob's web page that it's possible to add a switch
> to do this but I don't see how to do it.
> 
> May be Bob can help me?

So many messages... so little time...  :-)
The way I did it was to intercept the two drive select lines for D0 and D1
between the controller and the drives. These are pins 10 and 12 respectively.
The red wire is number 1.

Carefully cut between wires to separate a couple of inches of these two wires
(10 and 12). Now cut them and connect the controller-side of the wires to the
two common poles of a DPDT switch. Now connect the drive-side of the wires to
one pair of terminals on the switch, so that in one position the two lines go
straight through. Next criss-cross the drive-side wires and connect to the
other pair of switch terminals, so that when you toggle the switch, the Drive
Select lines are swapped. That's all there is to it.

I did this specifically so I could boot from either 5.25" drive or 3.5" drive.
Also incredibly useful is intercepting the Side-Select line (Pin 32) and run it
to an inverter. Connect the inverted signal to N.O. and non-inverted signal to
N.C. terminals of an SPDT toggle switch and then connect the common switch
terminal to the drives (Pin 32). You CANNOT read the back of a FLIPPY by
toggling the Side-select... you have to copy it over to DS FLOPPY before you
can do that.

With the above two switches you can access (and boot from) either side of
either floppy drive regardless of DOS, regardless of controller.

With regards to Color FOG requiring an FD502 controller, no it does not. It
requires DECB 1.1 or HDB-DOS, which also requires DECB 1.1 as its foundation.
ANY controller should work as long as it has the correct ROM version.

The DISK Basic ROM came in two versions AFAIK. 1.0 and 1.1. Even though the
CoCo3 states Disk Extended Color Basic 1.2 (or whatever), this is not telling
you the DISK ROM version. There are four different roms in the floppy equipped
CoCo3... Color Basic, Extended Color Basic, Super Extended Color Basic and the
Disk rom itself. Download Color FOG and run the installer, it will tell you if
you have DECB 1.1 or not.

Good luck,
Bob Emery


		
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