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From: cprice@mips.COM (Charlie Price)
Newsgroups: comp.arch
Subject: Re: Yet Another Upgrade Anecdote
Message-ID: <38620@mips.mips.COM>
Date: 9 May 90 21:34:11 GMT
References: <43777@iuvax.cs.indiana.edu> <1161.263f4987@gp.govt.nz> <423@dg.dg.com> <1173.2644246e@gp.govt.nz>
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Reply-To: cprice@mips.COM (Charlie Price)
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In article <1173.2644246e@gp.govt.nz> don@gp.govt.nz (Don Stokes) writes:
>
>Did DEC (or anyone else for that matter) ever build a QBUS-UNIBUS
>adapter?
>

There are (were anyway) at least a couple.
Many years ago at Storage Technology we used a "Qniverter".
I'm not certain about the manufacturer,
it might have been Able (Able Technologies?).

This product was a board that went into the first Qbus slot and
connected to the unibus backplane with a standard extender cable.
Of course there are problems in any such attempt at
transparent translation.
If you ignore Qbus block mode, the main stumbling block would be
that the unibus has an 18-bit address and the Qbus is up to 22 bits.

There isn't a whole lot an adapter can do about that transparently.
Since our use was to run some Qbus peripherals
(including some custom interfaces we had built)
on an 11/44 this was not a problem.
The reverse use, to run unibus peripherals from a Qbus
system with >256KB of memory would not have been transparent.

This illustrates something about the recent
marketing/sales-price discussion.
If there is a large enough need to be worth the effort,
and filling the niche is "safe enough",
someone will try to fill it.
-- 
Charlie Price    cprice@mips.mips.com        (408) 720-1700
MIPS Computer Systems / 928 Arques Ave. / Sunnyvale, CA   94086