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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!newshost.telstra.net!act.news.telstra.net!psgrain!news.uoregon.edu!tank.news.pipex.net!pipex!dispatch.news.demon.net!demon!radar.demon.co.uk!richard From: richard@radar.demon.co.uk Newsgroups: comp.unix.bsd.freebsd.misc,alt.comp.periphs.mainboard.asus,comp.sys.ibm.pc.hardware.systems,comp.os.linux.hardware,comp.sys.intel Subject: Re: PCI bus freq with CPU freq at (X * 40)Mhz? Followup-To: comp.unix.bsd.freebsd.misc,alt.comp.periphs.mainboard.asus,comp.sys.ibm.pc.hardware.systems,comp.os.linux.hardware,comp.sys.intel Date: Mon, 4 Mar 1996 21:45:36 GMT Organization: Anyone who pays me Lines: 44 Message-ID: <DnrJ41.1I0@radar.demon.co.uk> References: <DnpJqF.82n@info.elvisti.kiev.ua> X-NNTP-Posting-Host: radar.demon.co.uk X-Newsreader: TIN [UNIX 1.3 950515BETA PL0] Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:14901 alt.comp.periphs.mainboard.asus:11949 comp.sys.ibm.pc.hardware.systems:28559 comp.os.linux.hardware:32247 comp.sys.intel:66564 Andrew V. Stesin (stesin@elvisti.kiev.ua) wrote: : Sorry for ignorance, but what will be the frequency on a PC's PCI bus : when the CPU runs at main frequency of 40MHz (DX2/80, DX4/120 i.e.)? Depends on the chipset. Maybe 20MHz, maybe 33MHz, perhaps something else. PCI is rated at 0 to 33MHz. : I always thought that PCI will than run at 40MHz too. : But was told today that it will be only 20MHz?! Oh God. : How can I check this for sure, without running hated benchmarks, : but only by exploration of MB jumpers? Even if it is, it may be that IO speed is not as important as main memory speed. The ASUS PVI-486 SP3 only drops slightly in PCI speed going from 33 to 40MHz. : I was also told that having 40MHz will probably cause : an addition of extra wait states for cache and RAM access, : thus making a box considerably _slower_ for real work : than with 33MHz CPU main frequency, especially for UNIX-like OS : (FreeBSD in my case, but who cares). Any comments on this one? Again, depends on the motherboard. I have 2 486 motherboards, both based on the SiS 496/497 chipset. Both can handle 50MHz as easily as 33MHz (no extra wait states). One is an ASUS PVI-SP3, the other is by DTK Computer. : And, in case both statements are true, why bother looking : at (X * 40)MHz 486 CPUs at all? Because on a good motherboard it is faster. : P.S. I don't own a PCI box, but just planning to buy one, choosing : the best bang-per-buck configuration now. : Was considering AMD 160MHz (glorified 486, called 5x86, he-he :) : chip, which has 40MHz main freq and 4x multiplier. : Now I'm seriously considering AMD 133 part (this one is 33MHz, 4x). : Guys have a very nice opinions on it. You may be better off at the low end of Pentium market. Cyrix 6x86-100 on a cheap Triton motherboard is not that expensive. - Richard