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My question is how is their architecture doing regarding the assorted speculative execution baked-in issues and what kind of impact is there on the AMD processo

My question is how is their architecture doing regarding the assorted speculative execution baked-in issues and what kind of impact is there on the AMD processors compared to comparable Intel CPUs?

xvector 7y ago
Frightening lack of press around this. Basically all of Intel's and AMD's lineups are centered around high thread count right now. Completely useless if I can't reasonably enable SMT.
- pja 7y ago
  So far, AMD has only been exposed to the Spectre (branch cache) information leaks haven’t they? They aren’t vulnerable to Meltdown or any of the recent MDS information leaks because they don’t speculatively execute if the thread doesn’t have access rights. Intel chose to speculate regardless and fixup the register contents on instruction retirement, which is why they have had so many problems.
- makomk 7y ago
  AMD's chips apparently don't have the security vulnerabilities that make SMT unsafe to enable on Intel chips - they released a white paper explaining why MDS etc aren't possible and what exactly the boundaries are on their chips: https://www.amd.com/system/files/documents/security-whitepaper.pdf https://www.amd.com/system/files/documents/security-whitepap... It just didn't get a huge amount of press coverage.
PixyMisa 7y ago
Phoronix is the number one site for that sort of article. https://www.phoronix.com/scan.php?page=article&item=intel-mds-xeon&num=1 https://www.phoronix.com/scan.php?page=article&item=intel-md...
nolok 7y ago
Those affect Intel much, much more than AMD and once you include the fixes it always get better for AMD than without because, oversimplifying a lot, when doing branch speculation "Is it branch A or B ? I will guess A and pre compute that" Intel didn't bother with any access check during the prediction and only ran them after once confirmed it was indeed A (so it already had the result and merely did the ACL check), whereas AMD was already doing all the checks even during predition. That's why there is an entire range of such weakness that doesn't affect AMD while it hurts Intel very strongly.

My question is how is their architecture doing regarding the assorted speculative execution baked-in issues and what kind of impact is there on the AMD processors compared to comparable Intel CPUs?

xvector 7y ago

Frightening lack of press around this. Basically all of Intel's and AMD's lineups are centered around high thread count right now. Completely useless if I can't reasonably enable SMT.

pja 7y ago
So far, AMD has only been exposed to the Spectre (branch cache) information leaks haven’t they? They aren’t vulnerable to Meltdown or any of the recent MDS information leaks because they don’t speculatively execute if the thread doesn’t have access rights. Intel chose to speculate regardless and fixup the register contents on instruction retirement, which is why they have had so many problems.
makomk 7y ago
AMD's chips apparently don't have the security vulnerabilities that make SMT unsafe to enable on Intel chips - they released a white paper explaining why MDS etc aren't possible and what exactly the boundaries are on their chips: https://www.amd.com/system/files/documents/security-whitepaper.pdf https://www.amd.com/system/files/documents/security-whitepap... It just didn't get a huge amount of press coverage.

PixyMisa 7y ago

Phoronix is the number one site for that sort of article. https://www.phoronix.com/scan.php?page=article&item=intel-mds-xeon&num=1 https://www.phoronix.com/scan.php?page=article&item=intel-md...

nolok 7y ago

Those affect Intel much, much more than AMD and once you include the fixes it always get better for AMD than without because, oversimplifying a lot, when doing branch speculation "Is it branch A or B ? I will guess A and pre compute that" Intel didn't bother with any access check during the prediction and only ran them after once confirmed it was indeed A (so it already had the result and merely did the ACL check), whereas AMD was already doing all the checks even during predition. That's why there is an entire range of such weakness that doesn't affect AMD while it hurts Intel very strongly.