Am 09.02.2016 14:14, schrieb Thierry Godefroy: > On Tue, 09 Feb 2016 10:36:02 +0100, Peter Graf wrote: > >> Am 08.02.2016 21:19, schrieb Thierry Godefroy: >>> >>> Q60 @ 66MHz (overclocked 68060RC50): >>> 127.82 BogoMips >>> Writethrough cache mode: 24.937 VAX Mips/43813.5 Dhrystones/s (5M runs) >>> Copyback cache mode: 47.812 VAX Mips/84005.4 Dhrystones/s (5M runs) >> >> A 68060 with fully activated caches should deliver (almost) exactly >> twice the clock frequency in BogoMIPS. And for my machines, it did, at >> least under Linux. > > The memory cache mode (write back or write through) is irrelevant for > BogoMips since no data is written to the memory during the timing loop: > only the pipeline and execution units number count, and the 68060 indeed > can execute two simple instructions per clock.
As you wrote below, there is a little interrupt overhead, so it's better if they are on copyback. >> I can't explain myself why it is 127.82 and not 132.0 BogoMIPS. > > The maximum accuracy of the measure is determined by the granularity of > the timer (for BogoMips, it's the 50Hz frame timer, so the maximum error > is 2* 1/50th of a second on the timing, and since the timing loop lasts > for 10 seconds, the accurracy of the final measure is of 0.5% or so. > > There's also the problem of the linked frame timer routines: at each tick > of the 50Hz timer, even in supervisor mode, QDOS/SMS executes those > routines. Depending on how long they are and how many have to run, they > induce a (small, but measurable) overhead on any running job. I said I > made the measures with no other job running, but I got many extensions > loaded by default on my QDOS/SMS systems, some with scheduler loop > routines (mostly used by device drivers), so there's a slight overhead > (but it's the same overhead for all systems, since I booted with the same > extensions for all of them). That probably explains it. I must have seen it under Linux as suspected. But even there I got only 159.8 BogoMIPS when I retried under Linux. 157.9 under QDOS Classic. Can not work on my Q60 anymore since my CRT Monitor just died. Peter _______________________________________________ QL-Users Mailing List
