[MEncoder-users] Best multiplier for CPU efficiency?

[larrystotler at netscape.net]

 I've done some informal testing with a wide array of machines I have ay my disposal between myself and friends. I've found that some machines do better than others(a Duron 800 - 8x100 encoding xvid faster than a P3/800 - 6x133. Almost 30% faster due to the better FPU in the Duron). I've noticed that on some machines, using top under Linux, I don't get 100% cpu usage when re-encoding to mp3lame. For x264 and xvid, I generall get 100%. I've also noted that hyperthreading is extrememly beneficial on a 2.8Ghz Xeon with an 800Mhz FSB(almost 100% faster when running 2 encodings, one on each virtual cpu. ie both threads run full speed compared to running a single encoding non-hyperthreaded), but less helpful on a 2.67Ghz Xeon with a 533Mhz FSB(only about 20% faster running 2 individual encodings over 1 single encoding, non-hyperthreaded). Obviously, for some things, extra options like SSE and 3DNow! or Altivec, give a great boost. But, I am wondering where the diminishing returns start to kick in. In other words, at what point does a slower front side bus actually stop a processor from running at 100% usage? Obviously, Celerons are probaby the worst for this since they have such high multipliers.
 
 Take this example. My friend's Athlon 3000+ runs at 1.8Ghz. We've managed to overclock it to 2.3Ghz, but the FSB/Memory speed is only running at 213Mhz using the memory dividers, so the system technically now has a higher multiplier for the memory. So w've increased the multiplier to approx 10.8 instead of 9. I believe that re-encoding speed didn't scale as well as hoped because of this.
 
 I've seen a 10% boost in speed running a K6-3/400 at 3x133 vs 4x100. The 100Mhz test used the motherboard L2 as 512k L3, while the 133Mhz test had the motherboard L2 disabled.
 
 So, in other words, does it make more sense to go for a processor with the lowest multiplier to ensure that you are feeding it the data it needs to run at full speed verus a processor that has a higher multiplier. Like a Core2 4300 vs 6300. the 4300 has an 9x multiplier while the 6300 has an 8x multiplier(discounting the extra .060Ghz advantage the 6300 has)?
 
 Thanx
  
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