Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!uunet!munnari.oz.au!kaukau.comp.vuw.ac.nz!comp.vuw.ac.nz!gpwd!gpwrdcs
From: don@gp.govt.nz (Don Stokes)
Newsgroups: comp.arch
Subject: Re: Yet Another Upgrade Anecdote
Message-ID: <1173.2644246e@gp.govt.nz>
Date: 6 May 90 04:45:41 GMT
References: <43777@iuvax.cs.indiana.edu> <1161.263f4987@gp.govt.nz> <423@dg.dg.com>
Organization: Government Printing Office, Wellington, New Zealand
Lines: 42

In article <423@dg.dg.com>, lewine@dg.dg.com (Don Lewine     ) writes:
> In article <1161.263f4987@gp.govt.nz> don@gp.govt.nz (Don Stokes) writes:
>>On the subject of "upgrade by jumper"...
>>
>>I seem to recall a rumour floating around a few years ago, that a VAX
>>11/750 could be sped up by a factor of four by changing a couple of
>>resistors.  
> Not true.  The 11/750 was built out of gate arrays.  It was the first 
> mini-computer to be built out of gate arrays.  Each array had 400 gates.
> The gates were not very fast.  It would be possible to build an 11/750
> like machine using much faster gate arrays, but that is a different story.

It was just a rumour.  I suspect that the story came from the microcode
"upgrade" mentioned by another poster (who's name I forget).  Hey, we
didn't have news when this rumour went around; and NZ was a long way for
rumours to travel (hence my skepticism) 

>>DEC's pricing structures were always a mystery to me, particuarly in the 
> 
> I don't see any mystery here at all.  The newer machince were not only much
> faster, they were also much less expensive to build.  The idea was to get
> people to stop buying the old expensive to build machines and move them to
> the newer faster and more profitable machines.

The interesting part here is that they kept selling the old machines; the
/750 was around and still being sold long after the MicroVAX II was
announced, despite being a little quicker and a lot (half the price)
cheaper.  It could have been because people still wanted a low-end UNIBUS
VAX to allow upgrades from PDP-11s (QBUS PDPs weren't terribly popular
then) without having to change peripherals not supported by the QBUS
machines.  

Did DEC (or anyone else for that matter) ever build a QBUS-UNIBUS
adapter?  We run a VAXBI-UNIBUS adapter in our VAX 8200 to drive some
ancient synch/asynch comms boards (including a couple of DUP-11s,
remember them?) salvaged from our 11/750s before they were retired. 


Don Stokes, ZL2TNM    /  /                              PSI%(5301)47000028::DON
Systems Programmer   /GP/ Government Printing Office      Postmaster@gp.govt.nz
+64_4_496_5681______/  /__Wellington__New_Zealand________________don@gp.govt.nz
        It is morally wrong to allow naive users to keep their money.