On Wed, Aug 28, 2019 at 1:32 PM Larry McVoy <lm@mcvoy.com> wrote:
Perhaps Clem can shed some light on why DEC did a MIPS machine? 
I did not work for DEC at the time and obviously, I was not in the room, so this is what I can say I picked up.  Supnik would be a better person to ask.  That said, some things I do know about the time/and behinds the scene.
  • Jupiter and Prism had been canceled. 
  • Alpha did not yet exist (and would not for another 2 years)
  • Cutler had left for Microsoft etc..
  • Sun was clearly on its game
  • The VAX on a Chip just was not cutting it
  • RISC architectures were the hot item
Here is where I get fuzzy on details.
  • I believe a prototype (i.e. skunk works) MIPS was running at WRL in Palo Alto running Ultrix and DEC windows, I think using some sort of cheap ??PC?? chassis.
  • But the performance of the prototype was excellent and cost was cheaper than the current vax products.
  • Somebody sr, maybe Bob, shows this to Sr management and got the money to productize it.  The issue as making an official Ultrix for it was I know a big one.  Ultimately, DEC farmed that work out to us at LCC (with us eventually taking over all of Ultrix - MIPS and Vax).
So, I think the MIPS product was a holding pattern while DEC got it's strategy together. Alpha would really show up until later (I would leave LCC and go to DEC to be apart if that).   Also note Alpha was brought up/debugged on Ultrix and of course, Prism sort of had Ultrix on it.    But I think using the MIPS chip keep them in the game, when Vax was dying and RISC was the word on the street.

FWIW: The issue of OSF/1 was a different one.  The whole switching off Ultrix, getting to a new OS had been kicking around DEC for a while.  One of the arguments for Cutler had been his new Mica system was that it could run both Unix and VMS on top of it - i.e. a single OS kernel.  When Prism was canceled (along with Mica) and Cutler left, that was a huge hole for DEC's SW strategy.

Oppose Sun Forever (OSF) as it was formed to counter the Sun/AT&T move.  That gave DEC a way out.  But remember, OSF/1 on MIPS was actually not a full product.   What you got was what OSF had released, which is why it really more like a beta.    While it started down the path to being a product; and DEC did specifically made it available (primarily to Universities/Research types), DEC management was very reluctant to release it because they did not want to support it.  In fact, LCC was asked to give a bid on taking it on after we had taken over Ultrix.   DEC management already saw Ultrix/MIPS as a resource drag once Alpha finally had been committed. [ FYI: this was the same behavior as IBM on AIX/360 BTW.  Funny, how big companies sometimes do things like this]

I always said, asking customers (and the ISVs) to switch OS and ISA in one step was what caused a huge problem for DEC [along with the ISA being 64-bit only and ISV/customer code 32-bit dirty].   I've often wondered if a 32/64 bit OSF/1 MIPS stepping stone using the R4400 had been available, particularly with the Gem compiler suite (which they had but never released outside of DEC), it would have allowed the ISVs to move to Alpha quicker.   Having to do it all in one step, cost them 3 years and more importantly, by the time the code was 64-bit clean; Sun & PPC had a 64-bit system and took the ISVs with away.