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I'll be one of those to say that HT/SMT should probably die off unless the chipmakers learn how to make it secure. I'd rather have twice the physical cores for

by mtgx 8y ago

I'll be one of those to say that HT/SMT should probably die off unless the chipmakers learn how to make it secure. I'd rather have twice the physical cores for a little higher price anyway. However, Intel starting to sell chips without HT has nothing to do with the insecurity of HT and everything to do with the fact that they are trying to sell chips that are cheaper to make (or more profitable), while also being a little more competitive (price-wise) with AMD's offerings. But while they do this, they know they'll have a severe handicap in performance as long as AMD continues to sell competing products with SMT enabled. So their "solution" is to start making it "fair" in their benchmarks by using only half the cores or the SMT disabled for competing AMD products. One of the first clues that tells us this move is not a response to the recent security vulnerabilities of HT is that they started offering chips without HT only a few months after those discoveries were made. Do you really think something like planning to design and ship a product without HT happened only a few months earlier? No, this was decided at least a year and a half ago.

snovv_crash 8y ago
Not everyone runs programs they don't trust on hardware they don't own. These sidechannel attacks are really only an issue for consumers with JIT JavaScript, and for enterprise with shared hosting. For HPC, or consumer/professional applications eg. gaming, rendering, encoding, ie. all those places where performance actually really matters, SMT is a great way to get a decent boost in a lot of workloads.
- marmaduke 8y ago
  It seems like something that should be improved at the OS-level, where some workloads are untrusted and can'tb e HT'd next to others, whereas trusted software can be.
toast0 8y ago
I don't think we can know for sure why they disabled HT. There's arguments for both. It's certainly possible that during the long Spectre embargo, someone was looking around and realized HT was going to be a problem. It's also not that hard to disable HT -- it's a flag somewhere in the on chip settings, in some parts of their product line, it's already done as part of binning and market segmentation. It's just a matter of deciding to have more SKUs with that set. Actually removing the die space used for HT would be different, but then we'd see chip families released without HT in any SKU.

by mtgx 8y ago

snovv_crash 8y ago

Not everyone runs programs they don't trust on hardware they don't own. These sidechannel attacks are really only an issue for consumers with JIT JavaScript, and for enterprise with shared hosting. For HPC, or consumer/professional applications eg. gaming, rendering, encoding, ie. all those places where performance actually really matters, SMT is a great way to get a decent boost in a lot of workloads.

marmaduke 8y ago
It seems like something that should be improved at the OS-level, where some workloads are untrusted and can'tb e HT'd next to others, whereas trusted software can be.

toast0 8y ago

I don't think we can know for sure why they disabled HT. There's arguments for both. It's certainly possible that during the long Spectre embargo, someone was looking around and realized HT was going to be a problem. It's also not that hard to disable HT -- it's a flag somewhere in the on chip settings, in some parts of their product line, it's already done as part of binning and market segmentation. It's just a matter of deciding to have more SKUs with that set. Actually removing the die space used for HT would be different, but then we'd see chip families released without HT in any SKU.