[Coco] Coco drives single and double side question.

[Ghislain Harvey]

Thanks for the info.
SO if you have @ drive single sided, DIR0=drive1  DIR1=Drive2 .  What will
DIR2 and DIR3 give? IO error?

-----Message d'origine-----
De : coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] De
la part de Robert Gault
Envoyé : January-08-08 9:50 PM
À : CoCoList for Color Computer Enthusiasts
Objet : Re: [Coco] Coco drives single and double side question.

Ghislain Harvey wrote:
> Well not exactly. What I want is that DIR0 give me the same result as
DIR2.
> 

You can do that but only by corrupting your disk operating system and 
reducing the possible number of drives from 4 to 2; not advisable.

The drive table is contained in the DOS ROM and contains 4 values to be 
sent to the controller. The normal values are:
drive #   value
0         1
1         2
2         4
3         $40

In a double sided system where the back side of a drive is considered a 
second side, the values are:
drive #   value
0         1
1         2
2         $41
3         $42

Notice that $40 actually tells the controller to use head #2, back side 
of the drive. Tandy configured the controller so that the side select 
$40 accessed another drive.

The tables are located in the ROM at DOS1.0 $D7AA and DOS1.1 $D89D.

If you want DIR0 and DIR2 to look at the same disk content, change the 
drive #2 value to 1. You had better have a good reason for doing this 
because it is just plain wrong!

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