# SMPng question

Jesse Guardiani jesse at wingnet.net
Wed Nov 5 11:20:19 PST 2003

```Kevin A. Pieckiel wrote:

[...]

>>     Could I buy one of those cheap \$300 quad Xeon 500mhz
>>     compaq boxes on ebay and use it as a 2 Ghz compiler box?
>
> No, not really; you're going to lose some performance in just
> keeping up with multiple processors.  In other words, it's not
> a linear increase in performance when you add processors.

OK. That's what I thought. Do you have a figure on the amount
of performance lost managing multiple CPU's?

I'm looking at this from a cost perspective, essentially. Take
These two computers for example:

4 CPU 500Mhz Xeon w/1M cache and 1Gb RAM for \$350:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3054734970&category=1484

2.4 Ghz P4 Intel 800FSB (cache size unknown) and 1 GB Ram for \$600:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2763877081&category=51139

--------- Ratio Math for Cost ----------
\$350                        x
------          *          ---
\$600                       100

\$35,000         =          \$600x

58.33%          =           x
---------- End Ratio Math -------------

So, the 2.4Ghz machine is 58.33% more expensive than the
quad 500Mhz machine. If I could get 60%-70% of the performance
of the 2.4Ghz machine out of quad 500Mhz machine then I'd
deal, considering cost.

However:

--------- Ratio Math for CPU ----------
2,400 Mhz                  100
------                *    ---
2,000 Mhz (4x500Mhz)        x

200,000               =    2400x

83.33                 =    x
---------- End Ratio Math -------------

As shown by the above ratio math, the quad 500Mhz machine is
only 83.33% as powerful as the 2.4 Ghz UP machine, so the quad
500Mhz machine running SMPng would have to only incur 23.33%-13.33%
operating losses in order to reach my 60%-70% efficiency goal. :)

Anyone have an idea what SMPng per processor loss percentages
are?

The 2.4Ghz machine will probably blow away the quad 500Mhz
machine regardless since it has 400Mhz DDR RAM and an 800Mhz
FSB. Still, it would be really neat to see some benchmarks
on things like this for future decision making.

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