Path: utzoo!attcan!uunet!philmtl!philabs!ttidca!quad1!srhqla!csun!mx!cbcscmrs From: mx!cbcscmrs@csun.edu Newsgroups: comp.arch Subject: Re: Cycle Counter Message-ID: <2272@csun.edu> Date: 18 Aug 89 02:41:36 GMT References: <121192@sun.Eng.Sun.COM> Sender: news@csun.edu Reply-To: cbcscmrs@ma.csun.edu (Mike Stump) Distribution: comp Organization: CSU, Northridge School of Engineering & Computer Science Lines: 26 In article <121192@sun.Eng.Sun.COM> ram@sun.UUCP (Renu Raman) writes: >In article grunwald@flute.cs.uiuc.edu writes: >>When doing performance monitoring, benchmarking or profiling, you want >>a high-resolution timer. Some systems have microsecond timers, and >>those are considered pretty snazzy; I know I was overjoyed when I >>found one on the Encore. Normal machines, e.g., a Sun, have about 5 >>millisecond resolution. That's pathetic. > > Depends on what kind of a "normal" Sun you have. Anything since > SPARCstation should have a micro-second timer (only 21 bits tho') - so > 2 second is all you have if you want to watch anything. I like nanosecond timers, built into the instruction set! You can tell how far the head on the disk moved if you hit a page fault! The elxsi has a 25 nanosecond resolution process timer (to measure CPU time) and a CPU wide real time clock that also has 25 nanosecond resolution. Oh, unlike the 21 bits SPARCstation timer, on the elxsi you have to wait a little longer if you want to see the counter overflow. About 7,311 years and 284 days. Yes, that is 63 bits. :-) I think they are signed, and no, I don't know why... (Does it really matter at that point?) Syncing the thing up to a chimmer takes on a new meaning... :-) (NTP time servers...)