Date: Sat, 2 Aug 1997 16:10:06 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: tony@dell.com (Tony Overfield) Cc: terry@lambert.org, brianc@milkyway.com, hackers@FreeBSD.ORG Subject: Re: Pentium II? Message-ID: <199708022310.QAA00461@phaeton.artisoft.com> In-Reply-To: <3.0.2.32.19970802023853.0069c4c4@bugs.us.dell.com> from "Tony Overfield" at Aug 2, 97 02:38:53 am
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> >Dell was selling them. > > This is wrong! > > Dell sold no such thing as a "P5 DX/2-66"! You guys didn't call them that, but the memory bus was running at 33MHz; that's "clock doubled" in my book. I have a friend who had one until the Pentium math bugs reared their ugly heads (he was an IDE weenie, so he didn't care that PCI bus mastering failed on the thing). > >This was back when they were using the > >Saturn I chipset, which did not have DMA writeback notification > >connected from the macrocell (missing trace). > > Due to that bug, that version of the Saturn chipset does not support > write-back L2 caching and it is therefore configured by the BIOS to > use the L2 cache in write-through mode, though the L1 cache is always > write-back. The missing trace is not used or needed when the L2 > cache is in write-through mode. Unless a DMA initiated by a controller rather than the host occurs. Check the -hackers list archives for postings on disabling the L1 and L2 cache on these monstrosities... > >Dell also had 60MHz non-doubled chips > >available before the doubled 66's were available. > > Well, of course the 66 MHz chips were available after the 60 MHz > chips were, but they weren't "doubled." Maybe not; maybe the memory was just jumpered for an extra wait state; whatever; memory access was half as fast as it should have been in a reasonable implementation. > They probably would have, had the "doubled 66's" ever existed. > > >Just as my 486/50 kicks butt over the same chips. > > I doubt this, unless you're "stacking the deck" in some perverse > way, or you're simply dreaming. Of course I am, if an I/O intensive benchmark is "stacking the deck" and a CPU intensive benchmark is somehow "a good idea". I'm doing disk I/O, of course, and I am overclocking the EISA bus on the machine to 50MHz instead of 2x25. 50MHz EISA transfers data faster than 30MHz PCI... or 33MHz. 8-). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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