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Skylake just turned into a DUD for me: No BMI ?!?
Hello,
I just saw somebody on slashdot mention this: " From the errata: Executing CPUID with EAX = 7 and ECX = 0 may return EBX with bits [3] and [8] set, incorrectly indicating the presence of BMI1 and BMI2 instruction set extensions. Attempting to use instructions from the BMI1 or BMI2 instruction set extensions will result in a #UD exception. " http://www.intel.com/content/dam/www...pec-update.pdf This seems very bad to me. Without BMI Skylake would not be worth it to me ! =D Must have BMI support. I may have to skip Skylake or wait for steppings to fix it, but it says: NO FIX !? Wow... strange... Good idea to check errate before deciding on what processor to get from now on ! =D Bye, Skybuck =D |
#2
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Skylake just turned into a DUD for me: No BMI ?!?
On Thu, 20 Aug 2015 04:34:06 +0200, "Skybuck Flying"
Gave us: Hello, I just saw somebody on slashdot mention this: " From the errata: Executing CPUID with EAX = 7 and ECX = 0 may return EBX with bits [3] and [8] set, incorrectly indicating the presence of BMI1 and BMI2 instruction set extensions. Attempting to use instructions from the BMI1 or BMI2 instruction set extensions will result in a #UD exception. " http://www.intel.com/content/dam/www...pec-update.pdf This seems very bad to me. Without BMI Skylake would not be worth it to me ! =D Must have BMI support. I may have to skip Skylake or wait for steppings to fix it, but it says: NO FIX !? Wow... strange... Good idea to check errate before deciding on what processor to get from now on ! =D Bye, Skybuck =D Would have been nice if your parents had waited for stepping instead of failing to flush you. |
#3
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Skylake just turned into a DUD for me: No BMI ?!?
on 20/08/2015, DecadentLinuxUserNumeroUno supposed :
On Thu, 20 Aug 2015 04:34:06 +0200, "Skybuck Flying" Gave us: Hello, I just saw somebody on slashdot mention this: " From the errata: Executing CPUID with EAX = 7 and ECX = 0 may return EBX with bits [3] and [8] set, incorrectly indicating the presence of BMI1 and BMI2 instruction set extensions. Attempting to use instructions from the BMI1 or BMI2 instruction set extensions will result in a #UD exception. " http://www.intel.com/content/dam/www...pec-update.pdf This seems very bad to me. Without BMI Skylake would not be worth it to me ! =D Must have BMI support. I may have to skip Skylake or wait for steppings to fix it, but it says: NO FIX !? Wow... strange... Good idea to check errate before deciding on what processor to get from now on ! =D Bye, Skybuck =D Would have been nice if your parents had waited for stepping instead of failing to flush you. It would be nicer if you didn't repost his ****. |
#4
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Skylake just turned into a DUD for me: No BMI ?!?
On 2015-08-19 22:34, Skybuck Flying wrote:
Hello, I just saw somebody on slashdot mention this: " From the errata: Executing CPUID with EAX = 7 and ECX = 0 may return EBX with bits [3] and [8] set, incorrectly indicating the presence of BMI1 and BMI2 instruction set extensions. Attempting to use instructions from the BMI1 or BMI2 instruction set extensions will result in a #UD exception. " http://www.intel.com/content/dam/www...pec-update.pdf This seems very bad to me. Without BMI Skylake would not be worth it to me ! =D Must have BMI support. I may have to skip Skylake or wait for steppings to fix it, but it says: NO FIX !? Wow... strange... Jesus, so many bugs! First time I read an Intel CPU errata, are their CPUs all so damn buggy? I'm also waiting for the Tock... -- ! _\|/_ Sylvain / ! (o o) Member-+-David-Suzuki-Fdn/EFF/Red+Cross/Planetary-Society-+- oO-( )-Oo Mister Worf, show these children the airlock -Picard |
#5
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Skylake just turned into a DUD for me: No BMI ?!?
B00ze wrote:
On 2015-08-19 22:34, Skybuck Flying wrote: Hello, I just saw somebody on slashdot mention this: " From the errata: Executing CPUID with EAX = 7 and ECX = 0 may return EBX with bits [3] and [8] set, incorrectly indicating the presence of BMI1 and BMI2 instruction set extensions. Attempting to use instructions from the BMI1 or BMI2 instruction set extensions will result in a #UD exception. " http://www.intel.com/content/dam/www...pec-update.pdf This seems very bad to me. Without BMI Skylake would not be worth it to me ! =D Must have BMI support. I may have to skip Skylake or wait for steppings to fix it, but it says: NO FIX !? Wow... strange... Jesus, so many bugs! First time I read an Intel CPU errata, are their CPUs all so damn buggy? I'm also waiting for the Tock... Yes, bugs are normal. Each processor has around 100 errata, many with workarounds and a label in the appropriate doc that says "Won't Fix". Meaning if later revisions of the processor are released, the bugs stay in. This is why processors have Microcode caches and a Microcode loader in both the BIOS and in the OS. Some bugs remain unpatched, but are classed as "non-critical". For example, there was an AMD processor with an FPU "noise floor" issue. If you emitted enough back to back FPU instructions, it would cause a corruption of some part of the CPU. But the justification was, that modern compilers did not produce sequences of the required length. A person could, using assembler code, craft an executable to tickle the bug, but to what effect ? Why would you do that ? So that one remains unfixed and unpatched. Until the next processor design, where you'll have fresh new bugs. And how this works, is the "test program" for a processor, can last well past the launch date of the part. So if a processor is released for sale Jan 2015, some staff at the processor company might finish their last test case Jan 2016 or Jan 2017. Where I worked, we did similar things, ran the "critical" test cases first, and testing stretched well past release. In my department, 30% of manpower went into test. Whether that was money well spent, could be debated. Paul |
#6
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Skylake just turned into a DUD for me: No BMI ?!?
On 2015-08-20 22:19, Paul wrote:
Jesus, so many bugs! First time I read an Intel CPU errata, are their CPUs all so damn buggy? I'm also waiting for the Tock... Yes, bugs are normal. Each processor has around 100 errata, many with workarounds and a label in This is my first look at CPU bugs, before yesterday I always thought CPUs were mostly bug-free - I mean, Intel has been making CPUs processing the same instructions for so long, you'd think that by now they would have bullet-proof QA (on the other hand, the things are so complex, it's probably impossible to QA a CPU thoroughly). the appropriate doc that says "Won't Fix". Meaning if later revisions of the processor are released, the bugs stay in. Hopefully the worst ones are fixed by the next processor, e.g. Kaby Lake in this case. This is why processors have Microcode caches and a Microcode loader in both the BIOS and in the OS. Ah yes, the Microcode, I wondered what it was for. How efficient is it compared to hard-coded code? Also, Windows 7 has no idea about SkyLake. I've seen only one update on Win7 that mentioned Microcode, and with MS pushing W10, I would be surprised if they supported Skylake fixes from the O/S on W7. Motherboard manufacturers on the other hand, will... Some bugs remain unpatched, but are classed as "non-critical". For example, there was an AMD processor with an FPU "noise floor" issue. If you emitted enough back to back FPU instructions, it would cause a corruption of some part of the CPU. But the justification was, that modern compilers did not produce sequences of the required length. A person could, using assembler code, craft an executable to tickle the bug, but to what effect ? Why would you do that ? So that one remains unfixed and unpatched. Until the next processor design, where you'll have fresh new bugs. The only bug I knew of was the division bug on the original Pentium CPUs that made the news. That AMD bug sounds nasty, what if you do push enough FPU instructions in a row? Mathy programs could be affected, or demo writers could hit it; sounds bad not to fix something like this... And how this works, is the "test program" for a processor, can last well past the launch date of the part. So if a processor is released for sale Jan 2015, some staff at the processor company might finish their last test case Jan 2016 or Jan 2017. Where I worked, we did similar things, ran the "critical" test cases first, and testing stretched well past release. In my department, 30% of manpower went into test. Whether that was money well spent, could be debated. QA is very important, in my eyes. I don't care to see a cost analysis, if I buy something and it bugs on me, and the company that makes the product marks it as "No Fix" I am very displeased... Thanks for the info! Best Regards, -- ! _\|/_ Sylvain / ! (o o) Member-+-David-Suzuki-Fdn/EFF/Red+Cross/Planetary-Society-+- oO-( )-Oo "Au contraire, mon capitaine! HEEE'S BAAAACK!!!" -Q |
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