There’s recently been some interest in SCC performance measurements. There’s also been some confusion about what performance measuring features are available on the SCC.
It’s important to note that the SCC has P54C cores. The SCC belongs to the P5 family processors. Sometimes you may see the cores referred to as Gauss Lake cores. The differences between the P54C and Gauss Lake are minor. Gauss Lake has a larger L1 cache, a new memory type (MPBT), and a new instruction that flushes MPBT data from L1.
Performance monitoring capabilities are tied to the implementation dependent aspects of a particular processor. If you read one of the newer Pentium manuals, you will unfortunately get some misinformation. The best manual to read for a description about performance monitoring on the SCC is the 1995 Pentium Processor Family Developer’s Manual, which is posted on this site. Please look at Chapter 26.
With P6 came the ability to generate local APIC interrupts on counter overflow. This ability is not present in P5 family processors. For example, you can read in the Software Developer’s Manual Volume 3B:System Programming Guide, Part 2 in Section 30.16.5 that the P6 family processors provide the option of generating a local APIC interrupt when a performance-monitoring counter overflows. The SCC, however, belongs to the P5 family.
You still have access to performance counters. With the new Linux kernel (not yet available) you will have easier access. Some users have already begun performance measurements. Please look at http://communities.intel.com/message/117248#117248 . That thread has a description of work by Andrea Bartolini, Thomas Prescher, and Junghyun Kim. You can use the msr tools. CPUID shows that WRMSR and RDMSR are supported. Note that it also shows that MMX (also called SSE) is not, indicating that SCC is a member of the P5 family.
Here’s the output from a short program (source attached) that runs on a core and parses some information from the CPUID.
System contains a genuine Intel processor ...
System allows WRMSR and RDMSR...
System does not support MMX