Re: MACH chip question

From: Rodolphe Pineau <>
Date: Fri, 12 Jun 1998 10:59:55 +0200

At 09:43 12/06/98 +0200, you wrote:
>How do you know all this? Have you axamined the card or have you found the
>info somewhere else?

No but i spent a lot of time analysing the AB040 wiht an osciloscope. And
i've also a good behaviour of 680xx hardware. Anbd one of my friend is The
creator of the Centurbo 1 and The Centurbo 2 and is using an AB040 and take
some times to analyse all the outgoing signals with a numerical analyser.
The AB040 take 9 cycle to acces the falcon mother board because the Mach
have to rebuild a 32 bits word with 2 16 bit one so They need 2 board acces
and each of them take 4 cycle plus one in the mach for concatenation. The
seems also that interupt are filter by the match but i don't know exactly how!

>Some time back I talked to an engineer at Wizztronics about the AB040
>and their failure the Barracuda. According to him the Falcon needs
>a patched TOS to even boot. There a some instruction at boot up which
>will make the 040 hang, so it's necessary for the hardware on the
>accelerator to decode these instructions and alter them in order
>to let the 040 boot at all (make nops out of them). Does anyone have
>a comment about this? He claims this was the problem with the Barracuda
>and they could not release it as it needed a patched TOS to even
>boot. We all know that TOS 4.01 and possible 4.02 doesn't boot, so
>there must be something at boot up which goes wrong. I find it a bit
>hard to belive that the AB040 would decode instructions at bootup
>and alter them though.

I don't think tha AB040 Mach PLDs alters boot instruction. If i remember
well only tos 4.04 work with the AB040 so i thing that there was a
modification in the begining of the rom so that AB040 mmu doesn't crash at
boot (because i thing this is the problems). I will take a look at an old
tos and make comparision between this old one and my 4.04 to chek what are
the differences.

>As the AB040 hasn't got the fastest RAM access in the world, maybe it
>would be possible to change these 3 PLDs and make it faster. If someone
>just could get hold of those damned equations for the PLDs. It could be
>a interresting project for someone who has got lots of spare time...
I've got Mach databook so will take time to look if there is a solution to
read the internal code (may be not because of fuse protection)

>Also, do you happen to know anything about the expantion bus on the
>AB040? Is it just a plain CPU bus from the 040? Pinning?
I'm doing it and haven't finich it yet. This expantion bus have the upper
part of adress bus, and the lower part of data bus, There is some signals
that comme from one of the Mach that i haven't decode yet. In order to have
a real 32 bits bus we've got to use both trhe falcon expansioin port anf
the AB040 expansion bus. As soon as i've finish this work i will release
the pinout in this mailing list. I' could do this work but i haven't
enougth free time to buil any hardware for it.


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Received on ma. juni 15 1998 - 00:15:00 CEST

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