4 ms·

You forgot nVidia's Denver, that actually performed quite well. Agree on the Mill though.

CalChris 9y ago
Denver is not a VLIW; it's 7-way superscalar [1]. Haswell is 8-way. Wide superscalar is really common and has a lot of the advantages of VLIW without the impossible compiler headaches. [1] https://www.extremetech.com/computing/174023-tegra-k1-64-bit-denver-core-analysis-are-nvidias-x86-efforts-hidden-within https://www.extremetech.com/computing/174023-tegra-k1-64-bit... And the VLIW has to compete against that. There's only one place where VLIW has shown to have a survivable advantage and that's embedded.
- deepnotderp 9y ago
  It isn't an OoO, at least, not a 224 window OoO. 7-wide can simply mean that it has the decode and execution resources of 7 per cycle. It's a tablet core, they don't have a 7-wide OoO core in there. https://www.hotchips.org/wp-content/uploads/hc_archives/hc26/HC26-11-day1-epub/HC26.11-2-Mobile-Processors-epub/HC26.11.234-Denver-Darrell.Boggs-NVIDIA-rev4.pdf https://www.hotchips.org/wp-content/uploads/hc_archives/hc26... Also, the ee380 presentation: https://www.youtube.com/watch?v=oEuXA0_9feM https://www.youtube.com/watch?v=oEuXA0_9feM
  - CalChris 9y ago
    I was at the EE380 talk :). It's amazing how few people show up to EE380 these days. Yeah, Denver is in-order superscalar and it's a JIT but it isn't VLIW. Sad to say, they've tried JITing to in-order superscalar as well. They had a design win with the Nexus but even now NVidia is switching over to RISC-V for Falcon. It is not from lack of effort that the JIT approach hasn't really worked. It's competitive but not outstanding. Denver, from the EE380 talk, thrives on bad bloated code. It's not so good on good code. This is not a winning combination.
    - deepnotderp 9y ago
      Well, Falcon is intended to be a controller, not a (relatively) high performance core, so that's not an apples to apples comparison. If it's not VLIW, then what is it? In-order superscalar? You mean superpipelined or scoreboarded (like an ancient Cray?)? Bad bloated code is 90%+ of the code in the world ;) Also, shoot me an email at sixsamuraisoldier@gmail.com you seem to have some inside info on Denver, I'd love to chat (don't worry, I won't steal any secrets ;) )
- gpderetta 9y ago
  Haswell is generally considered 4-wide [1]. As far as I heard, Denver really is VLIW. I don't think there are many in-order [2] CPUs that are that wide. I think the article is using superscalar loosely (as in 'can execute more than operation per cycle' which is true for VLIW, although they are techinically all part of the same instruction). [1] apparently it can sustain 5 instructions per clock given some very specific instruction mix. [2] or out of order, really, Power8 being the exception.

Denver is not a VLIW; it's 7-way superscalar [1]. Haswell is 8-way. Wide superscalar is really common and has a lot of the advantages of VLIW without the impossible compiler headaches. [1] https://www.extremetech.com/computing/174023-tegra-k1-64-bit-denver-core-analysis-are-nvidias-x86-efforts-hidden-within https://www.extremetech.com/computing/174023-tegra-k1-64-bit... And the VLIW has to compete against that. There's only one place where VLIW has shown to have a survivable advantage and that's embedded.

deepnotderp 9y ago
It isn't an OoO, at least, not a 224 window OoO. 7-wide can simply mean that it has the decode and execution resources of 7 per cycle. It's a tablet core, they don't have a 7-wide OoO core in there. https://www.hotchips.org/wp-content/uploads/hc_archives/hc26/HC26-11-day1-epub/HC26.11-2-Mobile-Processors-epub/HC26.11.234-Denver-Darrell.Boggs-NVIDIA-rev4.pdf https://www.hotchips.org/wp-content/uploads/hc_archives/hc26... Also, the ee380 presentation: https://www.youtube.com/watch?v=oEuXA0_9feM https://www.youtube.com/watch?v=oEuXA0_9feM
- CalChris 9y ago
  I was at the EE380 talk :). It's amazing how few people show up to EE380 these days. Yeah, Denver is in-order superscalar and it's a JIT but it isn't VLIW. Sad to say, they've tried JITing to in-order superscalar as well. They had a design win with the Nexus but even now NVidia is switching over to RISC-V for Falcon. It is not from lack of effort that the JIT approach hasn't really worked. It's competitive but not outstanding. Denver, from the EE380 talk, thrives on bad bloated code. It's not so good on good code. This is not a winning combination.
  - deepnotderp 9y ago
    Well, Falcon is intended to be a controller, not a (relatively) high performance core, so that's not an apples to apples comparison. If it's not VLIW, then what is it? In-order superscalar? You mean superpipelined or scoreboarded (like an ancient Cray?)? Bad bloated code is 90%+ of the code in the world ;) Also, shoot me an email at sixsamuraisoldier@gmail.com you seem to have some inside info on Denver, I'd love to chat (don't worry, I won't steal any secrets ;) )
gpderetta 9y ago
Haswell is generally considered 4-wide [1]. As far as I heard, Denver really is VLIW. I don't think there are many in-order [2] CPUs that are that wide. I think the article is using superscalar loosely (as in 'can execute more than operation per cycle' which is true for VLIW, although they are techinically all part of the same instruction). [1] apparently it can sustain 5 instructions per clock given some very specific instruction mix. [2] or out of order, really, Power8 being the exception.