[Coco] [Color Computer] Floppy contoler Q

[Gene Heskett]

On Saturday 14 January 2006 23:47, Robert Gault wrote:

>Bit6 $FF40 is used by Tandy for drive select 3. However, the

> connection of this bit to the ribbon cable results in it also being a

> side select.

>

>When single sided drives are used, bit0=drive0, bit1=drive1,

>bit2=drive2, and bit6=drive3. With double sided drives and without any

>hardware changes to the controller or ribbon cable, bit0=drive0,

>bit1=drive1, and bit6= side select.

>

>You might think that 3 double sided drives could be used because bit6

>could be combined with any of the three bits 0, 1, or 2 resulting in

> 0, 1, 2, $40, $41, or $42. Unfortunately, the controller does not

> permit that because $00 turns off the drives. That leaves you with 1,

> $41, 2, and $42 or two double sided drives. You can however, have two

> double sided drives and one single sided drive at the same time with

> the third drive selected with $40.


Thats not entirely true Robert.  I've been running 3 double sided floppy 
drives on my coco's for nearly 20 years.  Os9 does this correctly at 
least, I don't know about DEB and clones as I don't run them.  All I 
did was put fully populated connectors on my cables.

-- 
Cheers, Gene
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