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Home machine, near-workstation class

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  • Home machine, near-workstation class

    I've been thinking for a while about building another home machine, this time near-workstation class.

    As a matter of fact, my day job IS silicon design, and I want to be able to do that on this machine. These days I'm mostly involved in the physical side of things, not that I wouldn't be getting back into some simulation in this machine's lifetime. But the current emphasis on the physical side makes AMD a possibility, since floating point won't be the be-all, end-all of performance for the anticipated major workload.

    Decent CPU, big memory, and it's the latter causing pause. If I'm talking big memory, there's part of me that thinks I should have ECC, and that's what's driving the dilemma here.

    Normally ECC memory means workstation-caliber everything, which means expensive motherboards, Xeon or Opteron processors, bufferred DIMMs, etc. It's very easy that way to more than double system cost. On the other hand AMD CPUs, at least Piledriver family have ECC already, and many regular-class motherboards support it. There is some penalty, in that a 32G motherboard will likely only support 24G when using ECC, but that's still pretty decent. With this scheme the only cost addition to a normal system is the extra cost of unbufferred ECC DIMMs. (Cheaper than bufferred DIMMs)

    Question 1 - Am I being over-paranoid at thinking I need ECC in the 16G-32G realm? (note that this is NOT gaming.)

    The obvious CPU choice today would be Piledriver/Vishera, but Steamroller is just around the corner, and I'd been planning on waiting for that. I did a little more reading last week, and I get the distinct impression that there will be no standalone Steamroller CPU - it's just going to be the core that Fusion products are built on.

    Question 2 - Do the Fusion product have Intel-style 80-bit floating point in the non-x86 part, or just standard single/double precision floating point? This question may not really matter if I'm using commercial simulation software tools, because Fusion support would be years away, if it were to ever even happen.

    Question 3 - Will any of the Fusion products support ECC? I just looked up and found the Opteron X2150 series which does, but again that's Opteron, which pushes me into server/workstation-class hardware and jumps the cost way up. Plus the X2150 doesn't seem to have the raw horsepower of the 8350+. (I know it's getting supplanted with a Piledriver-derived CPU next year, but from what I've heard it's still a reduced-core part.)

    Essentially, to I pull the trigger on a Vishera box now, wait because Steamroller really will come out as an AMx CPU, or give up on ECC and go over to the Dark Side with Intel? (I have a different machine doing quite well now, so I can afford to wait. OTOH a friend suggest that we're in the waning golden days of homebuilt deskside machines. They won't go away, but they're becoming a niche thing and the prices will rise because of that.)

  • #2
    Question 1 - Am I being over-paranoid at thinking I need ECC in the 16G-32G realm? (note that this is NOT gaming.)
    The ZFS-heals-memory-errors paper that's been linked in ZFS discussions over and over had this result: the DIMMs that had issues had many, the ones that didn't didn't get any with 99% confidence (number from memory).

    So if you ran memtest for 24h, and they all pass with zero errors, it's highly unlikely they will produce errors in the future. If they fail, RMA until you get working ones


    • #3
      That presumes no significant sensitivity to alpha errors. I agree with you on defects, but alpha hits aren't defects.

      I know that store-in-trench DRAM cells, especially when the I/O device is in epi, are quite insensitive to alpha errors. But I thought that most of the DRAM industry was in stacked-capacitor. I can see that the capacitor itself will not be sensitive, but how about the diffusion attached to the I/O device? Is it generally in epi too?