Date: Thu, 16 May 1996 22:05:43 +0300 (EET DST) From: Narvi <narvi@haldjas.folklore.ee> To: Terry Lambert <terry@lambert.org> Cc: hackers@FreeBSD.org Subject: Re: EDO & Memory latency Message-ID: <Pine.BSF.3.91.960516215023.25743H-100000@haldjas.folklore.ee> In-Reply-To: <199605161827.LAA17550@phaeton.artisoft.com>
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On Thu, 16 May 1996, Terry Lambert 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 ? > > > > > > 25 * 3 = 75 > > > > > > Multiply access latency by 3. > > > > Contrary to what some prefer to think, Pentium 75 run on the external > > speed of 50 Mhz - 1.5*50=75. So how about looking the figures over once > > more time? > > Was this supposed to be a memory bus or a data bus speed? I guess it was the memory speed and latency - I doubt he had his memory on the other side of the PCI bus. In the opposite case no-one would say that 60ns EDO memory is recomemded for 66Mhz external bus as the memory access would in any case be done at 33Mhz. > > PCI can't run faster than 33 -- on a 75, that means 25. > > I feel I can't argue against this - though why aren't they running it at some other speed than 1/2 of external and not 33/50 of it? I hate Pentium 75-s which lose to 486DX-80s in one of the components of graphics winmark... (everything else was exactly the same) :-( > Terry Lambert > terry@lambert.org > --- > Any opinions in this posting are my own and not those of my present > or previous employers. > Sander .sigless on the moment
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