Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ames!sun-barr!sun!kilowatt!raz
From: raz%kilowatt@Sun.COM (Steve -Raz- Berry)
Newsgroups: comp.sys.amiga.tech
Subject: Re: DTACK* or not to DTACK*, that is my question...
Keywords: hardware hairy hendersons VMA* VPA* DTACK* and their brothers.
Message-ID: <119763@sun.Eng.Sun.COM>
Date: 6 Aug 89 08:17:17 GMT
References: <119697@sun.Eng.Sun.COM> <7553@cbmvax.UUCP>
Sender: news@sun.Eng.Sun.COM
Reply-To: raz@sun.UUCP (Steve -Raz- Berry)
Organization: Sun Microsystems, Mountain View
Lines: 51

In article <7553@cbmvax.UUCP> grr@cbmvax.UUCP (George Robbins) writes:
>In article <119697@sun.Eng.Sun.COM> raz%kilowatt@Sun.COM (Steve -Raz- Berry) writes:
>> Ok, now for the even more advanced students, do the 8520's respond to
>> VMA* by issuing an INT6/2* ? And if so can I assume that Paula will
>> suck up this interrupt and generate an IPL code that I will have to
>> feed to my 68020 ??? Can I assert AUTO* right away when I detect an
>> interrupt ? Or do I have to wait until everybody goes tri-state before
>> I drop AUTO* ???

>Huh?  Interrupts are done in a simple, but not obvious way.  The processor
>does an ineterrupt acknowledge cycle.  The address lines during this cycle
>are clearly defined and based on the IPL being service.  The address selects
>ROM.  The vector numbers are read from ROM, not any peripheral device.
>Co-processor boards are free to do AVEC type interrupts if they do the
>function code decoding, the results are equivalent.  Real vectored
>with codes from the devices and whatnot aren't adequeatly supported by
>the expansion bus - no priority chains or encoding.

Ok, so you got me. I confused the name of the AVEC* line. I was thinking
about AUTOvectoring, and my fingers did the rest.
This is what I needed to know, thanks. 

>You sound generally confused about 68000 interrupts though.

Only slightly. It's not always easy dealing with custom hardware and
two different processors. If this was a simpler machine, I wouldn't have
had to ask ;-)

>Well, have fun, but beware of reventing the wheel.  There are reasonable
>coprocessor solutions out there from hacker kit to high dollar already.

>George Robbins - now working for,	uucp: {uunet|pyramid|rutgers}!cbmvax!grr


Hacker kit? Hmm, I haven't seen anything like this for the 2000. LUCAS
is the only thing that immediately comes to mind, and that's the wrong
Amiga. I won't settle for anything less than a accellorator that plugs
into the coprocessor slot and allows me the upgrade path to 32 bit ram.
I haven't seen anything on the market that I can personally afford.

I don't really mind if I re-invent things either, I'm doing this for
fun/education so it doesn't have to be original. Besides, I can put in
the stuff that *I* consider important.

As an added side affect, it's cheaper too.


---
Steve -Raz- Berry     Disclaimer: It wasn't me! I was volatilizing my esters.
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