4 ms·

If the benchmark has any cache misses at all then you also want to make sure everything about the memory configuration is the same, too, for a fair CPU benchmar

If the benchmark has any cache misses at all then you also want to make sure everything about the memory configuration is the same, too, for a fair CPU benchmark, right? Number of channels, latency, etc. No, the actual amount of RAM isn't directly relevant, but it seems like a possible brown m&m to me. (https://www.snopes.com/fact-check/brown-out/ https://www.snopes.com/fact-check/brown-out/)

dathinab 3y ago
> for a fair CPU benchmark, right? Number of channels, That's exactly where the differences comes from you want to max out the available memory channels on each device not have the same number. Same for latency etc. I mean your also not fixing the clock speed to 2GHz no boost or when comparing cars limit things just to the first 3 gears or similar. Because if you would add such artificial limits you won't compare fairly how fast the _max performance_ can be, it would be a very different comparison and wrt. evaluating max performance very unfair. Now you still need to e.g. have a fair choice of RAM, so preferably if possible use the same RAM sticks (and also use RAM which works equally well with both Intel and AMD). But what that means is that you _have to_ give the AMD system more RAM because it has more channels. Now you also _have to_ make sure that you benchmarks don't have any RAM pressure wrt. capacity. Also I'm not sure why you mention cache misses? Because number of cache misses is quite independent of RAM amount? Do you mean disk cache or swap misses instead, but I don't think the benchmark does disk I/O and shouldn't have swap either? But even if the benchmark only uses let's say 32GiB of memory for getting a proper GPU
xcv123 3y ago
> If the benchmark has any cache misses at all then you also want to make sure everything about the memory configuration is the same, too, for a fair CPU benchmark, right? Number of channels, latency, etc. No. Adding that memory bottleneck would make it an unfair and worthless comparison. If you are testing the maximum CPU performance then you need to eliminate those bottlenecks, not create them.

dathinab 3y ago

> for a fair CPU benchmark, right? Number of channels, That's exactly where the differences comes from you want to max out the available memory channels on each device not have the same number. Same for latency etc. I mean your also not fixing the clock speed to 2GHz no boost or when comparing cars limit things just to the first 3 gears or similar. Because if you would add such artificial limits you won't compare fairly how fast the _max performance_ can be, it would be a very different comparison and wrt. evaluating max performance very unfair. Now you still need to e.g. have a fair choice of RAM, so preferably if possible use the same RAM sticks (and also use RAM which works equally well with both Intel and AMD). But what that means is that you _have to_ give the AMD system more RAM because it has more channels. Now you also _have to_ make sure that you benchmarks don't have any RAM pressure wrt. capacity. Also I'm not sure why you mention cache misses? Because number of cache misses is quite independent of RAM amount? Do you mean disk cache or swap misses instead, but I don't think the benchmark does disk I/O and shouldn't have swap either? But even if the benchmark only uses let's say 32GiB of memory for getting a proper GPU

xcv123 3y ago

> If the benchmark has any cache misses at all then you also want to make sure everything about the memory configuration is the same, too, for a fair CPU benchmark, right? Number of channels, latency, etc. No. Adding that memory bottleneck would make it an unfair and worthless comparison. If you are testing the maximum CPU performance then you need to eliminate those bottlenecks, not create them.