[HN Gopher] Intel Raptor Lake 0x129 CPU Microcode Performance Im...
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       Intel Raptor Lake 0x129 CPU Microcode Performance Impact on Linux
        
       Author : dangle1
       Score  : 24 points
       Date   : 2024-08-11 21:00 UTC (2 hours ago)
        
 (HTM) web link (www.phoronix.com)
 (TXT) w3m dump (www.phoronix.com)
        
       | debo_ wrote:
       | > On a geo mean basis for 188 benchmarks run, the performance
       | overall was flat from this new BIOS / CPU microcode... For the
       | most part the performance was the same but there were some
       | exceptions observed...
        
         | 0x000xca0xfe wrote:
         | Data movement/branch intensive code seems to be affected most
         | (WireGuard -10%, some Python benchmarks -8%).
        
           | BearOso wrote:
           | The branching and the scripting language hit was unexpected.
           | It slows single-threaded programs the most. That means this
           | definitely wasn't caused by an out-of-spec high power limit
           | set on the motherboards. So the common theory was wrong.
           | 
           | Games seem to be unaffected. There was suspicion regarding
           | the timing of this patch and AMD's new processors coming out.
           | That now seems to be unfounded, with only a minimal effect on
           | consumer applications.
        
             | Dalewyn wrote:
             | >It slows single-threaded programs the most. That means
             | this definitely wasn't caused by an out-of-spec high power
             | limit set on the motherboards. So the common theory was
             | wrong.
             | 
             | No, low thread workloads draw more volts than high thread
             | workloads. This is easily observable using anything that
             | measures CPU voltages. Single threaded use cases seeing
             | more impact, if any, is completely within expectations.
             | 
             | That said, Intel said performance drops should be
             | negligible if any.
             | 
             | I haven't updated my system yet since ASUS's releases are
             | currently marked as beta, but I don't expect there to be
             | notable performance drops either. Granted, my 14700K in my
             | daily driver has been working perfectly fine since I bought
             | it and so have all the other Raptor Lake machines I care
             | for.
        
               | BearOso wrote:
               | Earlier reports believed the motherboard was setting the
               | total power limit too high, like 300W. That would have
               | affected multithreaded workloads.
               | 
               | The voltage spiking during mispredicted vdroop was
               | actually the cause.
        
       | PaulKeeble wrote:
       | I have seen a bigger hit on my 13700k on an MSI Z790 board. About
       | 2% on single threaded workloads due to the boost now not going
       | past 5.3Ghz but 20% on multithreaded like Cinebench. The
       | performance hit is really quite significant.
       | 
       | Its made even worse by the fact the pre microcode benchmark was
       | on a hand application of Intels Default power recommendations to
       | reduce damage, so 125W and limitations on amps and boost times.
       | Its now running on performance mode which can use 250W. I don't
       | understand how some people see no difference, others seeing a
       | little and I am seeing a lot. Something is going on here.
        
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       (page generated 2024-08-11 23:01 UTC)