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From: apratt@atari.UUCP (Allan Pratt)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: TT VME Bus, and extending it
Message-ID: <2952@atari.UUCP>
Date: 28 May 91 19:10:08 GMT
References: <17302@chaph.usc.edu> <1991May22.180217.27664@uvm.edu>
Organization: Atari Corp., Sunnyvale CA
Lines: 21

pegram@kira.UUCP (Robert B. Pegram) writes:
>[T]he TT's VME bus is only D(ata)16(bits), A(ddress)24 (one vme
>connector), which is fine for a Mega STE, but you need D32, A32 to
>really handle an 030.  I'm also not completely clear whether VME
>supports Bus mastering properly ...

The VME in a TT and a Mega STe is indeed A24/D16.  In addition, it is
slave-only: the VME board can't be a bus master.  It is not unreasonable
to suppose that a future machine from Atari might have full-sized VME
with A32/D32 and full bus mastership.

I have seen at least one product where you put the TT in a card-cage and
get larger-sized VME connections (6U; the TT only has 3U) but the bus is
still the same.  The only difference is the physical size and shape of the
VME cards you can plug in.  There is lots available in A24/D16, especially
if you aren't limited to 3U (as the TT and Mega STe are), but as I said,
the VME card(s) can't be bus master(s) in the current machines.

============================================
Opinions expressed above do not necessarily	-- Allan Pratt, Atari Corp.
reflect those of Atari Corp. or anyone else.	  ...ames!atari!apratt