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Date:      Mon, 30 Sep 1996 23:59:10 -0700
From:      "Michael L. VanLoon -- HeadCandy.com" <michaelv@MindBender.serv.net>
To:        Narvi <narvi@haldjas.folklore.ee>
Cc:        "David E. O'Brien" <obrien@nuxi.cs.ucdavis.edu>, freebsd-hardware@freebsd.org
Subject:   Re: H/W recommendation 
Message-ID:  <199610010659.XAA13490@MindBender.serv.net>
In-Reply-To: Your message of Mon, 30 Sep 96 23:26:46 %2B0300. <Pine.BSF.3.91.960930232410.7487C-100000@haldjas.folklore.ee> 

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>> It's pretty simple for real Pentiums (or 486s).  Anything that is an
>> even multiple of 33 1/3 (read things as 133.3... 166.667...) runs the
>> memory bus at 66 2/3 MHz (i. e. "166"MHz Pentium is 2.5 * 66.67MHz).
>> Anything that isn't an even multiple of of 33.3, and is an even
>> multiple of 30, runs the PCI bus at 60MHz.  The only other option
>> that's left is multiples of 25 (75MHz Pentiums).

>Grrrr..... Pentiums being "even multiplies of 30" (60, 120, 150) run the 
>memory bus at 60 Mhz and the PCI bus at 30 Mhz.

Argh.  That's what I meant.  Unfortunately, that's not what my fingers
typed.

>The Pentium 75 runs the 
>memory bus at 50 Mhz and the PCI bus at 25 Mhz. 75 == 1.5*50

That's what I implied (following the logic outlined above), but
apparently didn't make explicitly clear.  Multiples of 25: the memory
bus runs at 50MHz, and the PCI bus runs at 25MHz.

>> The PCI bus on a Pentium runs at half the memory bus speed (the speed
>> from the CPU to memory and cache).  486s run the memory bus at the
>> same speed as the PCI bus (i. e. 30 or 33.3MHz in most cases).
[...]

To clarify:

      Even      Memory   PCI bus
    Multiple  bus speed   speed
       MHz       MHz       MHz
    --------  ---------  -------
      33.3      66.67      33.3
      30.0      60.00      30.0
      25.0      50.00      25.0

-----------------------------------------------------------------------------
  Michael L. VanLoon                           michaelv@MindBender.serv.net
        --<  Free your mind and your machine -- NetBSD free un*x  >--
    NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3,
        Sun4/4c/4m, DEC MIPS, DEC Alpha, PC532, VAX, MVME68k, arm32...
    NetBSD ports in progress: PICA, others...
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