----- Original Message ----- From: "Stuart Adams" <[EMAIL PROTECTED]> To: <linuxppc-embedded at ozlabs.org> Sent: Thursday, January 27, 2005 11:29 AM Subject: MPC5200 bogomips
> > We are only seeing 263.78 bogomips on a MPC5200 running > at 396 MHz. > > Doesn't this seem way to low ?? With a 603e core I'd expect > 1 bogomip per MHz or better. > > The exact same kernel source running on an 8xx PPC gets about > 1 bogomip per MHZ and my 745 CPU board does 2 bogomips > per MHz ... the bogomip calibration code is the same for all > PPC architectures so it seem like it should be an apples-to-apples > comparison. > > -- Stuart > Ha! You almost sound like you are quoting me from when I first looked at bogomips on the 5200. Here's the story: If you drill down to where bogomips are calculated you will see that it is measuring the speed of a dbnz instruction. The calculation assumes 2 clocks per dbnz. So the 8xx comes out at 1 BogoMIP/MHz. The 5200 takes 3 clocks/dbnz in this loop, so you get .67 BogoMIP/MHz. Not to worry, it's only one specific scenario. Overall I've found the 5200 to be about 1.5 MIPS/MHz compared to 8xx 1 MIPS/MHz. Mark Chambers
