4 ms·

The VAX (2005)

32 points by TMWNN 1y ago

rjsw 1y ago
Another link for some history from the DEC side is this [1]. [1] https://simh.trailing-edge.com/dsarchive.html https://simh.trailing-edge.com/dsarchive.html
panick21_ 1y ago
If you want to learn about the history of VAX chips I very strongly recommend this oral history: Supnik, Robert oral history https://www.computerhistory.org/collections/catalog/102738264/search/collection:oral-histories--keyword:vax/ https://www.computerhistory.org/collections/catalog/10273826... If you have any interest in VAX or DEC or chip design in the 80s. This is a must watch. Later also goes into how Alpha was created in Part 2.
- kjs3 1y ago
  Bob Supnik is a really interesting guy. Probably best known these days for being a maintainer of the SIMH emulation environment. He's forgotten more about computers than most people will ever know.
  - panick21_ 1y ago
    That's why I love Computer History Oral interviews the knowledge is crazy.
  - Suzuran 1y ago
    The simh maintainer kicked Bob out a couple years back in a spat over containerization (no, not that kind) and changed the simh license to non-Free over it. A new fork has emerged that Bob is involved in, but it's not the same simh that can trace its lineage back to DEC SCP.
PaulHoule 1y ago
The trouble with the CISC vs RISC interpretation is that the x86 was CISC but trashed all other architectures in the 1990s especially RISC architectures including https://en.wikipedia.org/wiki/DEC_Alpha https://en.wikipedia.org/wiki/DEC_Alpha and Intel’s own https://en.wikipedia.org/wiki/Itanium https://en.wikipedia.org/wiki/Itanium I think it’s as simple as a mass market architecture that sells more units can justify more investment than anything that sells fewer units. If DEC had been able to steal market share from the 386 with a VAX based product it might have been able to take the 386’s place but from a business perspective they didn’t want to cannabalize sales of higher margin minicomputers. The transition from bipolar to CMOS was also difficult because it did mean a regression in performance, IBM addressed this in the 390 by introducing a clustering solution but it was a bold and risky move.
- fredoralive 1y ago
  x86 isn’t a VAX though, not all CISC architectures are equally complex (or RISC arch’s reduced), and VAX does have a reputation for being a particularly CISCy CISC. We don’t really know fully if the same tricks would have worked as well with it.
  - TMWNN 1y ago
    And, in fact, Mashey specifically discusses what you identified, and what Houle wrote (rushing to post a gotcha on HN, obviously without having read Mashey's lengthy writings).
    - kjs3 1y ago
      Yeah, always good to read it. He goes into some detail about a hypothetical VAX-based x86 killer, tho some of it is "when I had beers with the guys designing the VAX..." reminiscing. Comp.arch was something really special. Guys like Mash, John McCalpin, Bob Colwell, Eugene Maya, Mitch Alsup, Terje Mathisen...folks who really, really understood computers, what the real tradeoffs are, did actual homework instead of guessing, and were generally able to discuss the issues without being jerks. Good times.
  - PaulHoule 1y ago
    What I've read was that DEC had a huge amount of regret over the PDP-11 having too small of an address space. It could be that experience led them to think the answer to their problems was to be early to market in the 64-bit age with the Alpha. They did have VMS for the Alpha and later Win NT but high-powered RISC processors were a crowded space in the 1990s.
    - panick21_ 1y ago
      You can learn all about the details of how and why Alpha was developed: https://www.computerhistory.org/collections/catalog/102738264/ https://www.computerhistory.org/collections/catalog/10273826... Its in Part 2. If I remember correctly, it was basically 64bit because Alpha was basically a (good) virus inside of DEC. Or maybe like secret society that revolted against the leader of the company. Olson had killed 32 bit PRISM and they already had VAX that was 32 bit and people making processor for it. To get people all over DEC to buy into Alpha (Alpha barley had any budget of it own) it had to be something new, and winning 64 bit did make sense. Olson really killed basically everything that make sense, that DEC survived so long with Olson as CEO is kind of crazy. The amount of horrible decision starting as early as the early 70s is kind of crazy. VAX had also been early, driven by Gordon Bell not Olson, very few of the competitors had 32 bit processors then, and people like Data General and Prime struggled to develop them in response. Funny enough a hardware guy on the VAX team basically proposed RISC-like architecture but it was rejected because they optimized for code size. To bad that they didn't hit on the idea of compressed instructions.

The VAX (2005)

32 points by TMWNN 1y ago

rjsw 1y ago

Another link for some history from the DEC side is this [1]. [1] https://simh.trailing-edge.com/dsarchive.html https://simh.trailing-edge.com/dsarchive.html

panick21_ 1y ago

If you want to learn about the history of VAX chips I very strongly recommend this oral history: Supnik, Robert oral history https://www.computerhistory.org/collections/catalog/102738264/search/collection:oral-histories--keyword:vax/ https://www.computerhistory.org/collections/catalog/10273826... If you have any interest in VAX or DEC or chip design in the 80s. This is a must watch. Later also goes into how Alpha was created in Part 2.

kjs3 1y ago
Bob Supnik is a really interesting guy. Probably best known these days for being a maintainer of the SIMH emulation environment. He's forgotten more about computers than most people will ever know.
- panick21_ 1y ago
  That's why I love Computer History Oral interviews the knowledge is crazy.
- Suzuran 1y ago
  The simh maintainer kicked Bob out a couple years back in a spat over containerization (no, not that kind) and changed the simh license to non-Free over it. A new fork has emerged that Bob is involved in, but it's not the same simh that can trace its lineage back to DEC SCP.

PaulHoule 1y ago

The trouble with the CISC vs RISC interpretation is that the x86 was CISC but trashed all other architectures in the 1990s especially RISC architectures including https://en.wikipedia.org/wiki/DEC_Alpha https://en.wikipedia.org/wiki/DEC_Alpha and Intel’s own https://en.wikipedia.org/wiki/Itanium https://en.wikipedia.org/wiki/Itanium I think it’s as simple as a mass market architecture that sells more units can justify more investment than anything that sells fewer units. If DEC had been able to steal market share from the 386 with a VAX based product it might have been able to take the 386’s place but from a business perspective they didn’t want to cannabalize sales of higher margin minicomputers. The transition from bipolar to CMOS was also difficult because it did mean a regression in performance, IBM addressed this in the 390 by introducing a clustering solution but it was a bold and risky move.

fredoralive 1y ago
x86 isn’t a VAX though, not all CISC architectures are equally complex (or RISC arch’s reduced), and VAX does have a reputation for being a particularly CISCy CISC. We don’t really know fully if the same tricks would have worked as well with it.
- TMWNN 1y ago
  And, in fact, Mashey specifically discusses what you identified, and what Houle wrote (rushing to post a gotcha on HN, obviously without having read Mashey's lengthy writings).
  - kjs3 1y ago
    Yeah, always good to read it. He goes into some detail about a hypothetical VAX-based x86 killer, tho some of it is "when I had beers with the guys designing the VAX..." reminiscing. Comp.arch was something really special. Guys like Mash, John McCalpin, Bob Colwell, Eugene Maya, Mitch Alsup, Terje Mathisen...folks who really, really understood computers, what the real tradeoffs are, did actual homework instead of guessing, and were generally able to discuss the issues without being jerks. Good times.
- PaulHoule 1y ago
  What I've read was that DEC had a huge amount of regret over the PDP-11 having too small of an address space. It could be that experience led them to think the answer to their problems was to be early to market in the 64-bit age with the Alpha. They did have VMS for the Alpha and later Win NT but high-powered RISC processors were a crowded space in the 1990s.
  - panick21_ 1y ago
    You can learn all about the details of how and why Alpha was developed: https://www.computerhistory.org/collections/catalog/102738264/ https://www.computerhistory.org/collections/catalog/10273826... Its in Part 2. If I remember correctly, it was basically 64bit because Alpha was basically a (good) virus inside of DEC. Or maybe like secret society that revolted against the leader of the company. Olson had killed 32 bit PRISM and they already had VAX that was 32 bit and people making processor for it. To get people all over DEC to buy into Alpha (Alpha barley had any budget of it own) it had to be something new, and winning 64 bit did make sense. Olson really killed basically everything that make sense, that DEC survived so long with Olson as CEO is kind of crazy. The amount of horrible decision starting as early as the early 70s is kind of crazy. VAX had also been early, driven by Gordon Bell not Olson, very few of the competitors had 32 bit processors then, and people like Data General and Prime struggled to develop them in response. Funny enough a hardware guy on the VAX team basically proposed RISC-like architecture but it was rejected because they optimized for code size. To bad that they didn't hit on the idea of compressed instructions.