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Hi there.
Some time back, there was a thread on the subject of BogoMIPS accuracy
and resolution, and I commented that I would look into the situation
and explore it on the various systems available to me. I forget who I
made this comment to, and the relevant emails are no longer to be
found here, but here's the results anyway. All relate to ix86 class
systems as I have no others available.
1. The current calculation yields a result with a resolution of
8 bits, for an accuracy claimed to be slightly better than 1%
but which experiment has generally shown to be between 1.3%
and 1.5% of the best result. In this context, "best result" is
defined as being the result at the highest resolution that
remains stable.
2. On 386 class systems, the resulting figure remains stable when
the resolution is increased to 11 bits, and is stable on 21 of
the 23 systems in this class available to me when increased to
12 bits, but increasing it beyond that point only results in
random bits being added to the result.
3. On 486 class systems, the resulting figure remains rock stable
when the resolution is increased to 12 bits, but increasing it
beyond that point only results in random bits being added.
4. On the Pentium and P2 based systems available to me, the figure
remains stable when the resolution is increased to 14 bits in
every case, and to 15 bits on one of the Pentium class systems
available to me, but additional resoultion just adds random bits
to the result.
5. On the sole K6-2 based system available to me, the figure remains
stable when the resolution is increased to 16 bits, with random
bits added beyond that point.
I would therefore suggest that the enclosed patch be applied, which
increases the resolution to 12 bits, thus providing the best available
accuracy on all classes of ix86 system.
Best wishes from Riley.
+----------------------------------------------------------------------+
| There is something frustrating about the quality and speed of Linux |
| development, ie., the quality is too high and the speed is too high, |
| in other words, I can implement this XXXX feature, but I bet someone |
| else has already done so and is just about to release their patch. |
+----------------------------------------------------------------------+
* ftp://ftp.MemAlpha.cx/pub/rhw/Linux
* http://www.MemAlpha.cx/kernel.versions.html
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