Re: Q:040/060 MMU and Snooping

From: M Grove <mgrove_at_iwvisp.com>
Date: Wed, 10 Mar 1999 00:50:37 +0000

> If the Afterburner Tool Kit that Doug assembled (and the
> apps that Overscan provided with the A/B) enable the MMU
> 'after' the machine has booted, does this mean the MMU is
> disabled (MDIS LOW) by the Afterburner during reset and
> system initialization, then initializes it by software
> during the boot sequence (ala the autofolder)?
>
> According to the users manual;
> "MMU Disable disables the translation mechanism of the
> MMU's"
>
> If the MMU is disabled during initialization, does this mean
> that if TOS sends 030 MMU instructions to the 040/060, that
> they will be ignored and no error will occur?

I asserted MDIS continually last night (tonight/this morning:).
This made no difference with the 060 on the diagnostic cart, it booted
as usual. The 040 however, would not come up under TOS, only the
diagnostic cart. An error I am not sure I mentioned before was a
diagnostic error T4. The combel is not generating an address for the
screen display (with the 060 installed).
So I guess that the MDIS only affects the translation mechanism, but not
the MMU "tree".
>
> I also am not clear on the snooping aspects of the CPU's and
> the A/B. I remember Doug saying the A/B doesn't implement
> Snooping, and the option he included in V4.X of the TK kits
> is one of his own routines (which I think he recommends in
> V5 not to use).
>
> The 060 does not utilize the MI pin of the 040. According to
> the 060 docs, this pin must be tied high if it is utilized
> on the (040) system the 060 is fitted to. I monitored this
> pin with the 040 installed, and there is activity while the
> machine is booting, and during execution of applications. It
> is pulled low during reset. Could this pin being tied high
> continually cause problems with the Afterburner operation
> with regards to snooping?

I tried pulling the MI pin high with the 040 installed. It would boot
with the diagnostic cart, but would freeze just before the Fuji would
apear ( part of the Fuji was red). So it looks like that in some respect
the A/B (or the 040) is utilizing it. Noted also the diagnostic cart
will not work with the 060 if the MI pin is NOT pulled high.

Mike
Received on fr. mars 12 1999 - 17:12:08 CET