4 ms·

> but SMT wouldn't emerge until 2002 I think they're counting P4 hyperthreading, but I remember dual-CPU Pentium II boards.

buildbot 2y ago
IBM had SMT in 1968 - https://people.computing.clemson.edu/~mark/multithreading.html https://people.computing.clemson.edu/~mark/multithreading.ht...
- trynumber9 2y ago
  I am not following. The page says it was investigated but not done.
  - buildbot 2y ago
    It was done - ACS-1: https://en.wikipedia.org/wiki/IBM_Advanced_Computer_Systems_project https://en.wikipedia.org/wiki/IBM_Advanced_Computer_Systems_...
    - jylam 2y ago
      "Although the designs were never finished and no models ever went into production", so it was researched but not done..?
wtallis 2y ago
SMT isn't SMP.
adrian_b 2y ago
SMT (including that branded as Intel HTT) is something very different from multiprocessors, like the dual-CPU boards. The concept of multiprocessors was already well understood around 1963, i.e. the multiplication of the performance of a computer by the multiplication of the CPU hardware. On the other hand, the purpose of SMT is to enhance the throughput of a computer by ensuring that the existing execution units do not stay idle, by executing instructions from multiple program threads in order to keep them busy. The modern use of SMT has been started by a research paper published in 1992, as a proposed improvement to the superscalar out-of-order CPUs already popularized by IBM POWER, but the name SMT (simultaneous multi-threading) has been coined only later, in 1997 (in the IEEE Micro from September/October 1997). IBM had already used SMT in the experimental Advanced Computer System in 1968 (and they have filed for SMT patents in 1971: US 3,728,692 & US 3,771,138), but that project has been canceled and its superior architecture has been mostly forgotten for several decades. CPUs that could execute instructions from multiple program threads, but not during the same clock cycle, like in SMT (hence the "simultaneous" of SMT), are older than the IBM ACS, for instance such a processor with fine-grained multi-threading was the peripheral processor of CDC 6600 (in 1963). SMT can exist only in superscalar CPUs, because only there multiple instructions are initiated in the same clock cycle.

buildbot 2y ago

IBM had SMT in 1968 - https://people.computing.clemson.edu/~mark/multithreading.html https://people.computing.clemson.edu/~mark/multithreading.ht...

trynumber9 2y ago
I am not following. The page says it was investigated but not done.
- buildbot 2y ago
  It was done - ACS-1: https://en.wikipedia.org/wiki/IBM_Advanced_Computer_Systems_project https://en.wikipedia.org/wiki/IBM_Advanced_Computer_Systems_...
  - jylam 2y ago
    "Although the designs were never finished and no models ever went into production", so it was researched but not done..?

wtallis 2y ago

SMT isn't SMP.

adrian_b 2y ago

SMT (including that branded as Intel HTT) is something very different from multiprocessors, like the dual-CPU boards. The concept of multiprocessors was already well understood around 1963, i.e. the multiplication of the performance of a computer by the multiplication of the CPU hardware. On the other hand, the purpose of SMT is to enhance the throughput of a computer by ensuring that the existing execution units do not stay idle, by executing instructions from multiple program threads in order to keep them busy. The modern use of SMT has been started by a research paper published in 1992, as a proposed improvement to the superscalar out-of-order CPUs already popularized by IBM POWER, but the name SMT (simultaneous multi-threading) has been coined only later, in 1997 (in the IEEE Micro from September/October 1997). IBM had already used SMT in the experimental Advanced Computer System in 1968 (and they have filed for SMT patents in 1971: US 3,728,692 & US 3,771,138), but that project has been canceled and its superior architecture has been mostly forgotten for several decades. CPUs that could execute instructions from multiple program threads, but not during the same clock cycle, like in SMT (hence the "simultaneous" of SMT), are older than the IBM ACS, for instance such a processor with fine-grained multi-threading was the peripheral processor of CDC 6600 (in 1963). SMT can exist only in superscalar CPUs, because only there multiple instructions are initiated in the same clock cycle.