Date: Thu, 16 May 1996 22:38:49 -0700 From: "Michael L. VanLoon -- HeadCandy.com" <michaelv@HeadCandy.com> To: "Serge A. Babkin" <babkin@hq.icb.chel.su> Cc: narvi@haldjas.folklore.ee (Narvi), hackers@freebsd.org Subject: Re: EDO & Memory latency Message-ID: <199605170538.WAA15769@MindBender.HeadCandy.com> In-Reply-To: Your message of Thu, 16 May 96 16:47:46 %2B0600. <199605161047.QAA13555@hq.icb.chel.su>
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>> > 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
>You're right, I was wrong. So, the guestion gets yet more interesting :-)
The external local _memory_ bus runs at 50MHz. The PCI bus, on that
machine, would run at 25MHz. There's more than one bus...
>> 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.
Yes, ASUS says that my Pentium motherboard (Triton chipset) can use
70ns SIMMs for 60MHz memory bus (P120, P150, P180, etc.), but they say
I am supposed to use 60ns (or faster) SIMMs if I run the memory bus at
66MHz (P100, P133, P166, etc.).
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Michael L. VanLoon michaelv@HeadCandy.com
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