From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <392E2B84.EA7BE0DB@da-san.com> Date: Fri, 26 May 2000 16:45:08 +0900 From: Seungdong Lee MIME-Version: 1.0 To: Marcus Sundberg CC: Dan Malek , linuxppc-embedded@lists.linuxppc.org Subject: Re: 8240 BogoMIPS References: <39263EA0.69C60AA9@da-san.com> <3926CD15.441C87AB@embeddededge.com> <39289DA5.F0A5B8FF@da-san.com> Content-Type: text/plain; charset=EUC-KR Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Marcus Sundberg wrote: > Seungdong Lee writes: > > > Marcus Sundberg wrote: > > > I'm not very familiar with 82x0 processors, but doesn't 8240 use a > > > 603-core? When I worked with a 603ev running at 200 MHz I got > > > something like 133 BogoMIPS, so then the above value would be correct. > > > > > > > Good information. > > But, why it is 133 BogoMIPS? > > Because that's what a 200 MHz PowerPC 603 gives you. > Checking the BogoMIPS howto will show you one report of a 603, > running at 100 MHz and giving 66 BogoMIPS, which is at par with > our results. > > > I still think that the correct value is 400. > > Unless you have tried other 603-based sytems you have no reason to > think so. I repeat my statement from the previous post: > > > > The BogoMIPS can be used for rough sanity-checks when comparing > > > processors with identical cores and different clocks. For anything > > > else it's completely useless. > > //Marcus > -- > -------------------------------+----------------------------------- > Marcus Sundberg | Phone: +46 707 452062 > Embedded Systems Consultant | Email: marcus@cendio.se > Cendio Systems AB | http://www.cendio.com Hi guys, I got a reply from Motorola about instruction timing of bdnz. Conclusion is that it needs 3 cycles in 603. E-mail from Motorola is attached. -- Seungdong Lee DigitalDNA Help wrote: > Dear Seungdong Lee, > > in reply to your Service Request SR 1-UC2R (see details below): > > Instruction flow is discribed in "MPC603e & EC603e RISC Microprocessors > User's Manual" Chapter 6.3. > > BDNZ command executes as follow : fetch, dispatch, execute, writeback. > Last three steps are necessary to modify CTR. While first command > doesn't complete execute phase, next BDNZ command can't be dispatched > since they use CTR register both. So instruction takes up 3 cycles. > > I should note that if your loop isn't the void one then BDNZ latency can > occupy even 0 cycles. For example: > > _L: add > subf > subf > bdnz _L > > While executing of subf, bdnz will be prefetched and executed, moreover > due to static branch prediction add command will be speculatively > executed without awaiting of branch being executed. BDNZ effective cycle > time equals 0. > > ------- Details of your request: ------- > > Date Opened : 05/25/2000 00:10:46 > Product : XPC8240LZU200C > Category: Technical Request > > ---------- Subject ---------- > 8240 or 603e instruction timing > > ---------- Description ---------- > mtctr r3 > 1: bdnz 1b > > If r3 is 200*1000*1000, > how long does it take for MPC8240/200MHz CPU to execute bdnz loop? > I think that it should take only 1 second. But, the result is 3 > seconds. Can you explain my result? > > Manual says that branch instruction consumes only 1 CPU clock. > Apparently it is not true in my case. I found that other 603 based board > shows similar result. BogoMIPS value from Linux community can be the > evidence. BogoMIPS is 2*(loops per second)/1000000. > > Platform BogoMIPS Reported by > PowerPC 603/100 66.56 A. Costa > > PowerPC 603/200 131.19 Marcus Sundberg > > MPC8240/200 131.48 This is my result. > > Expected value is 400 in my case. > > Can I have any reasonable explanation about this? > Thanks. > > -- Seungdong Lee > ------- End of request details ------- > > > To review or update this Service Request, or to enter a new Service Request, please access Motorola's Customer Support web site at > http://www.motorola.com/semiconductors/support > > If there is ever an occasion when you cannot access Motorola's Customer Support web site, you can also contact us by sending an email to > DigitalDNA.Help@motorola.com > or by calling us at one of the following numbers: > > Americas 1-800-521-6274 7AM-6PM Phoenix > Asia +852-2666-8307 8AM-6PM Hong Kong > Japan 0120-191-014 8AM-5PM Tokyo > Europe +49-89-92103-559 9AM-5PM Munich > > Regards, > Motorola Semiconductors Customer Support ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/