4 ms·

When you say "MCM is as revolutionary as AMD64", does that mean Debian and RedHat and Windows and macOS, and all 3rd party applications, have to be recompiled f

by 0x0 9y ago

When you say "MCM is as revolutionary as AMD64", does that mean Debian and RedHat and Windows and macOS, and all 3rd party applications, have to be recompiled for a new architecture? Or is it simply an incremental speed-up of existing systems? I'm led to believe that if we're going to recompile The World as well as build new JIT javascript++ compilers, it will be for ARM64?

wtallis 9y ago
> does that mean Debian and RedHat and Windows and macOS, and all 3rd party applications, have to be recompiled for a new architecture? Or is it simply an incremental speed-up of existing systems? Neither. Multi-chip modules simply make it more economical to manufacture large processors. When you can make a 32-core CPU by connecting two 16-core silicon dies together, you'll have higher yields than if you try to make a monolithic 32-core die. There isn't necessarily any consequence visible to software, with the possible exception of having multiple NUMA nodes per physical socket.
- 0x0 9y ago
  So not an architectural paradigm shift, then - a mostly "invisible" incremental CPU improvement instead?
  - ihsw2 9y ago
    It's a pretty big increment that Intel has been unable to or unwilling to advance to. The message here is that if Intel drags their feet long enough then it'll take that much longer to catch up -- or, more to the point, they'll be forced to take more drastic (read: expensive) measures to catch up.
    - wtallis 9y ago
      Intel has produced multi-die CPUs in the past. They aren't doing it now because their fabrication advantage allows them to make bigger monolithic CPU dies than AMD can afford, so Intel doesn't have to incur the performance penalties that AMD's multi-die CPUs suffer from. At the same time, Intel has been very publicly preparing for the day that it makes sense for them to once again make multi-die CPUs, by making sure they have the technology to do it without the performance hit that is currently necessary. There's no heel-dragging from Intel on this issue. Once Intel's fab advantage is actually eliminated, they'll be forced to make multi-die CPUs to compete against AMD's multi-die CPUs. But every indication is that Intel will be ready to do multi-die better than AMD is doing multi-die. How much better is up for some debate, but it does look like Intel will have a leg up on EPYC's biggest weakness.
saas_co_de 9y ago
Multi-Chip-Module (Epyc) is just 4 separate dies wired together. (As Intel would derisively point out if is basically 4 Ryzen desktop chips glued together). The advantage of this architecture is that smaller chips are easier to manufacture because the probability of a random defect rendering the chip useless is lower and when a chip is bad it is not as great of a loss. Epyc chips run all existing software. There is extra work involved with Non-Uniform Memory Access (NUMA) where if you want software to actually use 32 or 64 cores simultaneously it has to be purposefully designed to take into account the architecture but that is not really any different than developing for multi-processor systems in the past. The point is that we have hit the ceiling on frequency scaling, which means more cores, and now we have hit the ceiling on core count scaling, so now it is going to be more CPUs, and the best way to do more CPUs is with MCMs.

by 0x0 9y ago

wtallis 9y ago

> does that mean Debian and RedHat and Windows and macOS, and all 3rd party applications, have to be recompiled for a new architecture? Or is it simply an incremental speed-up of existing systems? Neither. Multi-chip modules simply make it more economical to manufacture large processors. When you can make a 32-core CPU by connecting two 16-core silicon dies together, you'll have higher yields than if you try to make a monolithic 32-core die. There isn't necessarily any consequence visible to software, with the possible exception of having multiple NUMA nodes per physical socket.

0x0 9y ago
So not an architectural paradigm shift, then - a mostly "invisible" incremental CPU improvement instead?
- ihsw2 9y ago
  It's a pretty big increment that Intel has been unable to or unwilling to advance to. The message here is that if Intel drags their feet long enough then it'll take that much longer to catch up -- or, more to the point, they'll be forced to take more drastic (read: expensive) measures to catch up.
  - wtallis 9y ago
    Intel has produced multi-die CPUs in the past. They aren't doing it now because their fabrication advantage allows them to make bigger monolithic CPU dies than AMD can afford, so Intel doesn't have to incur the performance penalties that AMD's multi-die CPUs suffer from. At the same time, Intel has been very publicly preparing for the day that it makes sense for them to once again make multi-die CPUs, by making sure they have the technology to do it without the performance hit that is currently necessary. There's no heel-dragging from Intel on this issue. Once Intel's fab advantage is actually eliminated, they'll be forced to make multi-die CPUs to compete against AMD's multi-die CPUs. But every indication is that Intel will be ready to do multi-die better than AMD is doing multi-die. How much better is up for some debate, but it does look like Intel will have a leg up on EPYC's biggest weakness.

saas_co_de 9y ago

Multi-Chip-Module (Epyc) is just 4 separate dies wired together. (As Intel would derisively point out if is basically 4 Ryzen desktop chips glued together). The advantage of this architecture is that smaller chips are easier to manufacture because the probability of a random defect rendering the chip useless is lower and when a chip is bad it is not as great of a loss. Epyc chips run all existing software. There is extra work involved with Non-Uniform Memory Access (NUMA) where if you want software to actually use 32 or 64 cores simultaneously it has to be purposefully designed to take into account the architecture but that is not really any different than developing for multi-processor systems in the past. The point is that we have hit the ceiling on frequency scaling, which means more cores, and now we have hit the ceiling on core count scaling, so now it is going to be more CPUs, and the best way to do more CPUs is with MCMs.