Here's an interesting message I received.  Note that the LX chipset is no
longer Intel's newest, but the remarks still apply:

=======================Forwarded Message============================
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

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ICQ 8603107

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