Re: Q:040/060 MMU and Snooping

From: M Grove <>
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.

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

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