- Aug 20, 2000
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Okay, been doing some extremely light reading on CPU cache properties recently with all the new articles on the design of the X-Box and other consoles out. I'm not mistaken, CPUs almost universally lean towards using the set associatively mapped caching system. Now, in Anand's Hardware Behind the Consoles - Part I: Microsoft's Xbox, he writes:
"The CPU that powers the Xbox is a Coppermine based Pentium III with only 128KB L2 cache. While this would make many think that the processor is indeed a Celeron, one of the key performance factors of the Pentium III that is lost in the Celeron core was left intact for this core. The Coppermine core was left with an 8-way set associative L2 cache instead of the 4-way set associative cache of the Celeron. Based on what we've seen with the Coppermine and Coppermine128 (Celeron) cores we estimate that the 8-way set associative L2 cache gives this particular core a 10% performance advantage over the Coppermine128 core of the Celeron."
I can't help but wonder what that could imply for my pitiful Celeron 466. I had always figured 4-way associativity was the optimal setup for a mere 128KB of L2 cache - but this X-Box neutering has put doubts in that. Is there any other significant difference between the X-Box's Cumine CPU and the Celeron128 I've got that would make 4-way better to use than 8-way?
I also vaguely remember an option in software (in wCPUid, I think) that allowed a user to edit the block associativity of his CPU, am I just imagining that or is that possible? Hell, if it's in my best interests to go to 8-way associative mode and actually possible to do, I'm there.
Thanks in advance.
"The CPU that powers the Xbox is a Coppermine based Pentium III with only 128KB L2 cache. While this would make many think that the processor is indeed a Celeron, one of the key performance factors of the Pentium III that is lost in the Celeron core was left intact for this core. The Coppermine core was left with an 8-way set associative L2 cache instead of the 4-way set associative cache of the Celeron. Based on what we've seen with the Coppermine and Coppermine128 (Celeron) cores we estimate that the 8-way set associative L2 cache gives this particular core a 10% performance advantage over the Coppermine128 core of the Celeron."
I can't help but wonder what that could imply for my pitiful Celeron 466. I had always figured 4-way associativity was the optimal setup for a mere 128KB of L2 cache - but this X-Box neutering has put doubts in that. Is there any other significant difference between the X-Box's Cumine CPU and the Celeron128 I've got that would make 4-way better to use than 8-way?
I also vaguely remember an option in software (in wCPUid, I think) that allowed a user to edit the block associativity of his CPU, am I just imagining that or is that possible? Hell, if it's in my best interests to go to 8-way associative mode and actually possible to do, I'm there.
Thanks in advance.