Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!caen!hellgate.utah.edu!cc.usu.edu!slsw2
From: slsw2@cc.usu.edu
Newsgroups: comp.sys.dec
Subject: Re: pdp-11's
Message-ID: <1991Jun24.093746.48196@cc.usu.edu>
Date: 24 Jun 91 09:37:46 MDT
References: <ROCKER.91Jun21192228@bucsf.bu.edu> <1991Jun22.041102.1509@spcvxb.spc.edu>
Distribution: comp
Organization: Utah State University
Lines: 14

In article <1991Jun22.041102.1509@spcvxb.spc.edu>, terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr.) writes:
> Recent advances (in geological terms) such as
> block mode DMA and the PMI have made the Q-bus almost as fast as, and in
> many cases, faster than, the Unibus.

I spent a lot of time looking at the QBus and UNIBUS some years ago. With
block mode the QBus peaks at about 3 1/3 MB/s. UNIBUS peaks at 6 2/3 MB/s;
a memory module can support this throughput using 70 ns static RAM.

The main problem with UNIBUS as far as modern systems go is that it has a
limited address range; 256KB as opposed to 4MB for the QBus.

Roger Ivie
slsw2@cc.usu.edu