[Coco] Coco drives single and double side question.

[Ghislain Harvey]

Thank for this verry valuable info.
I think that was confused me is that My father (who own the coco3) Have the
DISTRO controller and 2 "hand made drive" they are not standard. They are
not tandy official drive.
I talk to him a bit and DECB isn’t supposed to be hacked. He say the is 2
special wired he connected to drive that allow access to the other side of
the disk when we DIR2/DIR3.
I checked and Indeed there are 2 wired numbered 1 and 0.
I may take a picture for people here today because it is very special and
unusual.
Ghislain

-----Message d'origine-----
De : coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] De
la part de Frank Swygert
Envoyé : January-10-08 9:36 AM
À : coco at maltedmedia.com
Objet : Re: [Coco] Coco drives single and double side question.

You had me confused too, but Rogelio and Robert Gault cleared it up... I
think! You really need to download "Tandy's Little Wonder". Click on the
link, then click on the READ ME FIRST file, then the two PDF files. You'll
have a wealth of basic (and advanced!) info for the CoCo. I believe there is
a program in there to access the back sides of drives, among other mods. 

I'm going to reiterate some of what Rogelio and Robert said here....

1. DECB (Disk Extended Color BASIC -- the CoCo disk system) was designed to
operate up to four single sided 35 track (~158K) disk drives, but was really
only expected to operate with two. The original drive cables had teeth
removed from the connector and the drives had all the drive select jumpers
on. The position the drive was in on the cable then determined what drive
number it was. The last position was drive 0, the "middle" (between
controller and drive 0 connectors) was drive 1. Later cables (for the CoCo3,
and the last of the CoCo2 systems) had all the teeth in the connectors and
the drive select jumpers were used. 

2. Standard 360K double sided drives will work, but only the "front" side
will be active unless DECB is modified. This can be done permanently by
burning a new ROM chip, or temporarily by running a program to modify DECB. 

3. Early Tandy drives will usually access 36 tracks, not just the standard
DECB 35, and some will access 37 or 38. Later Tandy drives were 40 track,
but DECB was never modified to access more than 35 for backward
compatibility. 

3. A common modification program is ADOS (or ADOS3 for the CC3). This has
lots of options! You go through the program listing, edit the options you
want, then: A - run the program and use the options from memory (temporary)
or B - have the program burned into a ROM chip to be placed in the
controller (permanent). Other "DOS" programs such as JDOS did basically the
same thing, but Art Flexser's ADOS was the premiere DECB modification
program -- pretty much a standard. 

4. Accessing the back of drives 0 and 1 as drives 2 and 3 is one common mod,
accessing the full 40 tracks is another. Using the back sides as 1 and 3
allows backups from 0 to 1 as if two standard drives were being used. 

5. To access four single sided drives just make a cable and plug them in. 

6. The drive controller can physically access THREE double sided drives.
Tandy wisely used the side select line as the drive 3 (fourth drive) line.
This allows the controller to access the "back" head of three drives. DECB,
however, is limited to four drives total, so the third drive isn't
accessible. Under OS-9, however, this feature becomes very useful! 

7. You can have three drives physically connected, DECB will just ignore the
third one IF it's been modified to access the back sides of two as 2 and 3.
Boot OS-9 and it ignores the DECB ROM -- it will access all three drives,
both sides, as single or double sided drives (depending on the drives and
Os-9 drivers used). I had two 360K drives in my system with ADOS burned to
access the back sides as 2 & 3, and a 720K 3.5" drive connected that only
OS-9 would access. All were connected to the same controller by the same
cable.

8. I can't think of anything else! D/L the book, it has ALL the answers in
it, and you can always ask here! 

----------------
Date: Tue, 08 Jan 2008 21:43:09 -0500
From: Ghislain Harvey <ghislainharvey at videotron.ca>

What I really want is that my system react as if I have 2 single side drive.

I have 2 double side drive.
So that's why I say DIR2 will give me the same thing as DIR0

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)


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