Date: Thu, 16 May 1996 13:19:46 +0300 (EET DST) From: Narvi <narvi@haldjas.folklore.ee> To: "Serge A. Babkin" <babkin@hq.icb.chel.su> Cc: hackers@freebsd.org Subject: Re: EDO & Memory latency Message-ID: <Pine.BSF.3.91.960516130639.25743B-100000@haldjas.folklore.ee> In-Reply-To: <199605160309.JAA29241@hq.icb.chel.su>
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On Thu, 16 May 1996, Serge A. Babkin wrote: > I have just tried lmbench and the numbers it gives are looking > slightly strange for me. It shows memory latency upto 500ns while > I have 60-ns EDO memory in a Pentium/75 box. Okay, its external > clock is 25MHz, this gives 40ns, one wait state, it gives another 40ns, > it gives 80ns, but why the overhead is over 400ns ? The external bus of the Pentium 75 should be 50Mhz. It is 1.5x50, not 3x25. 60ns EDO sounds like an overkill for a Pentium 75 though... I would use a quicker processor and (120) with ordinary memory (fast-page, 70ns) - but the likes may vary. And I am (like others might) having the dreams of SRAM-only computer, no matter how one with more/faster processors + ordinary memory might perform. > > Can it go from some VM subsystem activity ? I have 16M of RAM in my box > and I runned lmbench with 8M maximal buffer size. The latency grows > with the size of buffer. Is it possible that when > the size of buffer grows the VM subsystem moves the non-recently used > pages to some pool and when they are accessed again it gets the VM fault > and remaps them back to that process? > > Thanks! > > -SB > Sander .sigless on the moment
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