Re[2]: 8270 performance
From: Ricardo Scop <hidden>
Date: 2003-12-09 00:02:37
Hello Jean-Denis, Monday, December 08, 2003, 6:11:30 PM, you wrote: JDB> Ricardo, JDB> Jaap-Jan,
quoted
quoted
I would expect the bogomips number to be somewhere near the core clock (like 8xx).Well, I think the numbers are pretty fair, assuming that the bogomips number reflect a certain amount of external memory accesses at 66 MHz external bus clock.
JDB> It has more to do with pipelining! JDB> Hopefully, there ain't any memory access during calibration... JDB> (except, of course, when the instruction cache is disabled!) JDB> I didn't look at the documentation, but the execution of a branch probably occurs later in the pipeline of a 8260 than for the 860. It probably looses one more cycle. The calibration relies on JDB> the execution speed of function __delay (arch/ppc/kernel/misc.S), which loops on a branch instruction 'bdnz'. Ooops, I should learn to read the source code before making any assumptions. Sorry for the mistake, and many thanks for the lesson! -Scop. JDB> Regards, JDB> -------------------------------------------- JDB> Jean-Denis Boyer, Eng. JDB> M5T Centre d'Excellence en Télécoms Inc. JDB> 4283 Garlock Street JDB> Sherbrooke (Québec) JDB> J1L 2C8 CANADA JDB> (819)829-3972 x241 JDB> -------------------------------------------- ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/