Oxide and Friends Twitter Space: May 10, 2021

• [@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?t=699) This was the debate between Roger Faulkner and Jeff Bonwick: register windows
  • Roger Faulkner (RIP) thought they were horrific
• [@12:35](https://youtu.be/79NNXn5Kr90?t=755) Register fishing: Bryan’s version and Adam’s version > When you want to know the state of some other process, you have to flush > those register windows to memory to be able to recover the stack trace.
  • [@14:30](https://youtu.be/79NNXn5Kr90?t=870) Delay slot > We sat around the lunch table talking about how crazy it would > be to have a branch that executed right after a branch.
  • DCTI couple (delayed control transfer instruction)
  • [@15:31](https://youtu.be/79NNXn5Kr90?t=931) “Well, the instruction set doesn’t allow that..” story > Bedlam. As far as Solaris kernel discussions go, bedlam.
  • Leibniz vs. Newton
• [@20:14](https://youtu.be/79NNXn5Kr90?t=1214) Annulled branches
• [@22:17](https://youtu.be/79NNXn5Kr90?t=1337) Praise for SPARC
  • SPARC address space identifiers > When we were porting Solaris to x86, and deciding what fraction of the > address space would belong to the kernel vs the user, it felt disgusting to me.
• [@25:26](https://youtu.be/79NNXn5Kr90?t=1526) Software-filled TLB > They just didn’t have the room to cram a hardware page table walk into the chip.
  • MIPS would give you a trap on a VAC conflict (virtual address cache)
• [@27:34](https://youtu.be/79NNXn5Kr90?t=1654) It was slow, it was late, and it had a lot of problems, it was wrong.
  • UltraSPARC-III, code-named “Cheetah” > It’s weird, I compile this thing over and over, and every 80th time when > I compile and run it, it’s 40x slower..
  • UltraSPARC-IV+, code-named “Panther”
• [@32:17](https://youtu.be/79NNXn5Kr90?t=1937) Does the Viking I-cache bug ring a bell?
  • SuperSPARC, code-named “Viking” > You’d have to DC balance the I-cache. If you had too many zeros, > they’d start flipping to ones.
  • E-cache parity error > It was due to everything but high energy particle strikes.
  • Radioactive boron in our SRAM manufacturing process
• [@38:52](https://youtu.be/79NNXn5Kr90?t=2332) “Move it further from the tube” story > When you’re going to have a customer do something, you have to remember there’s > a human being on the other end of that. You cannot have them chasing your theories. > You need to be transparent and honest with them.
• [@42:25](https://youtu.be/79NNXn5Kr90?t=2545) Micron DRAM story
• [@44:38](https://youtu.be/79NNXn5Kr90?t=2678) High priced consultants and cosmic rays > They literally lined the roof with lead.. and it didn’t change the error rate at all!
• [@46:47](https://youtu.be/79NNXn5Kr90?t=2807) And the SRAM manufacturer was..
  • We’re competing with HP Superdome and..
• [@48:11](https://youtu.be/79NNXn5Kr90?t=2891) Aftermarket
  • TurboSPARC
  • Ross Technology
  • Ultra 1, code-named “Electron”
• [@51:34](https://youtu.be/79NNXn5Kr90?t=3094) What’s that tapping sound? > Seeing how that particular sausage was made, very very slowly, was discouraging.
  • Regatta On a Chip
  • UltraSPARC-T1, code-named “Niagara” 
    • [@57:15](https://youtu.be/79NNXn5Kr90?t=3435) The only thing we could get to run fast was benchmarks..
  • “Balanced” computing
• [@59:18](https://youtu.be/79NNXn5Kr90?t=3558) Sun Fire V880, code-named “Daktari”
• [@1:04:14](https://youtu.be/79NNXn5Kr90?t=3854) RISC
  • Stanford MIPS, Berkeley RISC, IBM 801, IBM POWER
  • Oral History of David Patterson > A bunch of grad students at Stanford and Berkeley were able to make a CPU > that was faster than the industry. RISC was a very big deal when it happened.
  • IBM ROMP microprocessor 
    • Academic Operating System AOS
• [@1:06:04](https://youtu.be/79NNXn5Kr90?t=3964) Intel 432 “The only constants you need are 0 and 1”
  • Revisiting the Intel 432
  • Robert Colwell’s “Performance Effects of Architectural Complexity in the Intel 432” paper
• [@1:09:12](https://youtu.be/79NNXn5Kr90?t=4152) Machine learning in the 80s?
  • Bill Joy: Open Systems Imperative video ~53mins
  • Bill Joy: The Future Doesn’t Need Us, ca. 2000
• [@1:11:37](https://youtu.be/79NNXn5Kr90?t=4297) The best historical analog for Oxide? > I loved that it was deliberate hardware-software co-design.
  • IBM AS/400 > Bill is amazing. He’s clearly the smartest person I’ve ever known. > But you never know what time scale he’s operating in, whether he’s telling you > to do something for tomorrow or for the next century.
  • Optative voice
• [@1:14:42](https://youtu.be/79NNXn5Kr90?t=4482) How early in Sun’s history were people talking about doing their own CPU?
  • Laura’s blog entry on the LPC55 vulnerability
  • Scout threads
• [@1:17:11](https://youtu.be/79NNXn5Kr90?t=4631) Finding SPARC bugs > I had a little Sun 4c that I had cranked up to 26k hertz, > and at 26k hertz it stopped at the banner message. > And I came in the next morning and it was at the login prompt! > This little poor machine had managed to boot! > I hit enter and it immediately panicked.
  • Processor state register (PSR), processor interrupt level (PIL)
• [@1:20:35](https://youtu.be/79NNXn5Kr90?t=4835) OpenBoot, Forth
• [@1:21:54](https://youtu.be/79NNXn5Kr90?t=4914) Long lived E10K, code-named “Starfire”
• [@1:24:01](https://youtu.be/79NNXn5Kr90?t=5041) Invasive physical attacks
• Tom Lyon and Joseph Skudlarek’s USENIX 1985 paper: All The Chips That Fit
  • Happy Meal Ethernet
• Sun keyboard photo
• [@1:29:56](https://youtu.be/79NNXn5Kr90?t=5396) The real secret of Sun’s success is that we built them to make ourselves happy. > Open source software in general, you develop it for yourself. > That way there’s at least one person who likes it.