Episode Details

Oxide and Friends Twitter Space: May 10, 2021

A Requiem for SPARC with Tom Lyon

We’ve been holding a Twitter Space weekly on Mondays at 5p for about an hour. In addition to [@bcantrill](https://twitter.com/bcantrill) and [@ahl](https://twitter.com/ahl), speakers included special guest Tom Lyon plus Joshua Clulow, Dan McDonald, Dan Cross, Tom Killalea, Theo Schlossnagle, Antranig Vartanian, and [@perlhack](https://twitter.com/perlhack).

We recorded the space; the recording is here.

Some of the topics we hit on, in the order that we hit them:

• [@2:06](https://youtu.be/79NNXn5Kr90?t=126) SPARC 30th anniversary dinner > SPARC was an amazing achievement for its time, > but there were some nasty trade-offs made.
• [@2:56](https://youtu.be/79NNXn5Kr90?t=176) illumos announcement on the end of SPARC support
  • SPARCstation 2
• [@4:37](https://youtu.be/79NNXn5Kr90?t=277) “There is no photography allowed in the bring-up lab” story
  • SPARCstation 1 (code-named Campus) > They bricked their first CPU..
• [@6:23](https://youtu.be/79NNXn5Kr90?t=383) UltraSPARC-II E-cache parity error
• [@8:51](https://youtu.be/79NNXn5Kr90?t=531) Register windows > Most people don’t know, about that first SPARC, > there was no integer multiply or divide..
  > It would trap on the instructions.
• I feel so decadent, I’ve just been sprinkling multiplications around my code for years.
• [@9:55](https://youtu.be/79NNXn5Kr90?t=595) popc instruction (also called Hamming Weight)
  • IBM Stretch 1961, and the one-of-a-kind IBM Harvest made for the NSA
  • Henry Warren’s 2002 Hacker’s Delight Ch. 5 shows a ~20 instruction algorithm (no branches, only adds/shifts/masks by constants) > Warren: According to computer folklore, the population count function is important to the > National Security Agency. No one (outside of NSA) seems to know just what they use it for, > but it may be in cryptography work or in searching huge amounts of material.
  • According to Agner Fog, Ice Lake performs popcnt with a 3 cycle latency, and Zen 3 with just 1 cycle latency.
  • Phil Bagwell’s 2001 Ideal Hash Trees depend on pop count > Bagwell: Note that the performance of the algorithm is seriously impacted > by the poor execution speed of the POPCT emulation in Java, a problem > the Java designers may wish to address. 
    • Persistent versions of Bagwell’s trees are used for the built-in hash maps of Clojure, and in libraries for Scala etc.
• [@11:39](https://youtu.be/79NNXn5Kr90?