[Coco] Question about MPI behavior

[Paulo Lindoso]

If memory serves, the reason why the drive controller must be in slot 4 was
bus timing of sorts.

I remember reading somewhere (Rainbow, list...) that if you used the
controller in another slot, you might get intermitent problems due to
timing problems;  it kinda makes sense for low-frequency circuits such as
the CoCo, but I have never tested it myself.



On Tue, Apr 17, 2012 at 10:55 AM, Robert Hermanek
<rhermanek at centurytel.net>wrote:


> Anyone know why the MPI manual states that a drive controller must be in

> slot 4?  I would think with the POKE trick discussed here, a controller

> would work in any slot as long as you set the active I/O properly.

>

> And that got me thinking about someone's previous post, asking if you can

> run more than one disk controller in a system, and we got into talking

> about changing I/O ports/etc.  If you had more than one disk controller in

> MPI, after booting the ROM in one as per normal, in slot 4 etc, what would

> stop you from using the $FF7F poke to switch your I/O to slot 3 and using

> the devices conencted to another disk controller?

>

> I have no plans to do or test this, but someone was asking about multiple

> controllers a few days (weeks?) ago...

>

> ----- Original Message ----- From: "Darren A" <mechacoco at gmail.com>

>

> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>

> Sent: Monday, April 16, 2012 7:28 PM

>

> Subject: Re: [Coco] Question about MPI behavior

>

>

>  On Mon, Apr 16, 2012 at 5:43 PM, Robert Hermanek wrote:

>>

>>> That was the problem, thanks so much. I'm not familiar with the $FF7F

>>> control register, I'll have to look at the MPI manual for that. Sounds

>>> like

>>> if I then wanted to use the registers of the rs-232 pak itself, I'd have

>>> to

>>> POKE myself back to slot 1. Good to know!

>>>

>>>

>> The RS-232 pak hardware registers are not selected by the SCS* signal.

>> They are fully decoded through the address lines and will always

>> respond, regardless of the active slot.

>>

>> Darren

>>

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>>

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-- 
-------------------------------------------------------------
Paulo Lindoso
paulo.lindoso at gmail.com
http://about.me/pbal<http://email.about.me/wf/click?c=e86tqVWFYsEogZdu8cwmbpAZwRtFkPjZS8Z3nwSDfjU%3D&rp=TDQggGXPgxMn1%2FQoMR%2F7Bsr00fO9wne%2B4zDSBQ93vWI1BH%2FOlrnU7zrQ0H0iAWgQyYyB6YfryJhLcifwbBLZ98yd6yex7cp06Yzq3Q1SplHrq%2FIu7OFPSwv8LqPdUbWL&u=njPbVRRXSvmg3PMz9cXBSg%2Fh0>