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Politics : Formerly About Advanced Micro Devices

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To: James Yu who wrote (23912)	10/3/1997 1:01:00 PM
From: Ali Chen	of 1571808

James: news about LX, that might explain why PC-makers refuse to use it: ===== message start ======== 10/2/97 From: halwh@mv.mv.com (Hal Hardenbergh) Organization: MV Communications, Inc. Newsgroups: comp.arch Buy an AGP-Compliant Motherboard! Run Slowly! ---------------------------------------------- It turns out that AGP-compliant chipsets will run more slowly than non-AGP compliant chipsets even when AGP is not in use. The need for AGP-CPU arbitration apparently slows the DRAM timing vs. standard non-AGP chipsets. The facts: These are DRAM timing figures for a 66 MHz bus and 60 nsec EDO DRAM for the various Intel chipsets (I have all the data sheets downloaded in .PDF format). Believe it or not, the 440FX data sheet does _not_ give the complete timing numbers (np = not provided). The chipsets are listed in chronological order. page hit row miss page miss 430FX 7/2-2-2 9/2-2-2 12/2-2-2 430VX 6/2-2-2 9/2-2-2 12/2-2-2 430HX 5/2-2-2 8/2-2-2 11/2-2-2 440FX np/2-2-2 np/2-2-2 np/2-2-2 430TX 5/2-2-2 8/2-2-2 11/2-2-2 440LX (8/9)/2-2-2 (10-12)/2-2-2 (12-13)/2-2-2 <-- AGP The AGP-compliant 440LX chipset for the Pentium II is Intel's newest and slowest chipset where DRAM access is concerned. I assume this is because the chipset has to arbitrate between CPU and AGP access to system DRAM, and stall the CPU when AGP is in operation. For a page hit, the 440LX is slower by 3 or 4 clocks at 66MHz, or 12 to 16 CPU clocks (!) at 266 MHz. That's a lot of CPU clocks to stand idle - all because AGP systems put the 3D texture map, which most people will never use, in the wrong place. The right place for the texture map DRAM is on the video board, where it will provide superior 3D video performance vs AGP and will not impact system DRAM performance. Intel "invented" AGP when system DRAM was $20/megabyte. Right now it's $2.56/megabyte and dropping. There is no longer any economic justification for AGP. There was never any technical advantage for AGP. Did you notice that the recent reviews of the 300 MHz P II with the LX AGP chipset all pointedly commented about how slow the system was for a 300 MHz CPU? This performance deficiency is real. [The newish 430TX chipset uses a 3.3V Vcc, and for that reason some- times does not work well in desktop PC systems. The I/O (address and data) line voltage swings do not match up well with some parts commonly used in PC desktop motherboard design. Well, Intel did intend the TX for portables.] Hal W. Hardenbergh ==== end of message =========

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