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From: Terje Mathisen <terje.mathisen@tmsw.no>
Newsgroups: comp.arch
Subject: Re: Why VAX Was the Ultimate CISC and Not RISC
Date: Mon, 3 Mar 2025 16:34:35 +0100
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Anton Ertl wrote:
> BGB <cr88192@gmail.com> writes:
>> It almost seems like they could have tried making a PDP-11 based PC.
> 
> I dimly remember that there were efforts in that direction.  But the
> PDP-11 does not even have the cumbersome support for more than 64KB
> that the 8086 has (there were PDP-11s with more, but that was even
> more cumbersome to use).
> 
> DEC also tried their hand in the PC-like business (DEC Rainbow 100).

When I was hired as the PC guy in Hydro (that Fortune-100 corporation 
with 77K employees in 130+ countries) in 1984, I took over all 
PC-related stuff (HW/SW/OS/add-on HW etc) while the guy who hired me 
kept his belowed DEC Rainbow which he felt had the better architecture:

For one thing they did not break Intel's rules about where to place the 
interrupt vectors. In hindsight this was a bad decision since 100% 
compatibility with Microsoft Flight Simulator was an absolute 
requirement at the time.

> They did not succeed.  Maybe that's the decisive difference from HP:
> They did succeed in the PC market.

For some definition of success, i.e they were sufficiently worse at PCs 
to later merge with Compaq who was the first significant vendor in the 
PC Compatible marketplace. Columbia beat both of them by half a year or 
so, but faded away a bit later.

Terje


-- 
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"