KA630 guru?

From: Hans B PUFAL <hansp_at_citem.org>
Date: Thu Aug 5 18:29:48 2004

Antonio Carlini wrote:

> I've fallen a little behind in my reading
> so I forgot to follow this thread.
>
>
>>I now favour the "executing out of prefetch buffer" theory, reinforced
>>by the following comment snippet someone sent me, supposedly
>>taken from
>>the source to MicroVAX console ROMs:
>>
>>; To turn on MMGT and execute the following REI depends
>>on a "quirk"
>>; of the MicroVAX chip. Namely, if the MTPR and REI
>>instruction are
>>; both fetched as part of the same instruction
>>prefetch, then the
>>; REI will be executed regardless of the enabling of
>>mmgt. However,
>
>
> OK. So it sounds like you have strong evidence for
> a chip bug here. The chances of getting it confirmed
> are slim :-) - there was a list of Waivers granted
> to various VAX implementations, but seeing it was
> on a need-to-know basis. If the console code has
> such comments in, it's best to believe them.
>
> I guess they let the bug pass both because it's
> relatively harmless and would have been expensive
> to fix once the chip had been finalised.

Have you taken this up with Bob Supnik, he of SIMH fame?

   -- HansP
Received on Thu Aug 05 2004 - 18:29:48 BST