C[omp]ute

From: "andrew cooke" <andrew@...>

Date: Sun, 11 Mar 2007 21:57:00 -0400 (CLT)

Below is a record of my experiments.  There may be some errors, as the
data were transcribed from rough notes on scraps of paper.  The basic
conclusions are:

- fine details don't matter too much as there are so many things to vary
  (in other words, there's more than one way to hit the same bottleneck)

- the board is very nice at "helping" with various automatic choices, but
  that also becomes a limiting factor (see below)

- using stock components it's possible to get a 25% performance gain.

- none of the above changed voltages (except for any "automatic"
  adjustments) and there seems to be very little risk involved
  (only once did I have to hard reset the motherboard).

- typically the board either works, or fails to boot.  Very few
  settings gave unstable behaviour later.

- top configurations are:

  fCPU    fClock                  t           speed
  2.77GHz 346MHz DDR922 5-2-2-18  0.78        +28%
  2.66GHz 333MHz DDR888 4-4-4-11  0.79, 0.81  +23-27%
  2.77GHz 346MHz DDR692 4-4-4-11  0.80, 0.80  +25%
  2.77GHz 346MHz DDR692 5-2-2-18  0.83        +20%
  2.13GHz 266MHz DDR712 4-4-4-11  1.00        (reference)

  where "t" is normalised time relative to the base config and
  "speed" is the relative % speed increase (100 * (1/t - 1))

The values given for frequency and memory settings are taken from
Memtest86+, v1.7.  They do not always agree with the BIOS settings (see
details below, where BIOS settings are given on first line).

The details below show that it is difficult to reach the settings achieved
directly.  Instead the boards "automatic" values need to be used -
entering direct values typically gives board lockups.  This may be because
using automatic settings also modifies voltages (which I otherwise left
alone).

I don't really understand memory timings, but 5-2-2-18 does look odd.  I
will probably go with 2.66GHz 333MHz DDR888 because it gives good
performance with less worry about CPU heating, and avoids the odd memory
values.  I have run that setting overnight on Memtest with no errors.
Note the strange memory multiplier (which fits those "4" values into "3").
 The FSB is then 1665MHz.

Andrew


overclocking notes

090307 - all standard voltages

a  3.00GHz   375MHz  DDR750   4-4-4-11  fail

b  3.00GHz   375MHz  DDR563   4-4-4-11  fail

c  2.80GHz   350MHz  DDR933*  4-4-4-11  fail

d  2.77GHz   346MHz  DDR923*  4-4-4-11  fail

e  2.77GHz   30%     Auto     4-4-4-11  kernel 13m31s
             346MHz  DDR692   4-4-4-11

f  2.77GHz   30%     DDR922*  Auto      overlooked candidate?
             346MHz  DDR922*  5-2-2-18  (see below)

g  2.77GHz   30%     Auto     Auto      kernel 14m02s
             346MHz  DDR692   5-2-2-18

h  2.66GHz   333MHz  DDR888*  4-4-4-11  fail

i  2.66GHz   333MHz  DDR666   4-4-4-11  kernel 13m24s
             333MHz  DDR888*  4-4-4-11  (compare w above!)

j  2.66GHz   333MHz  DDR1110  Auto?     fail

k  ?         888/DDR667       Auto      fail

l  2.33GHz   10%     Auto     Auto
             292MHz  DDR584   5-2-2-18

m  2.24GHz   5%      Auto     Auto
             280MHz  DDR746*  4-4-4-11

n  2.13GHz   Auto    Auto     Auto      kernel 16m53s
             266MHz  DDR712*  4-4-4-11  mobo default

fastest cpu speed attained was 2.77GHz (e)
fastest 4-4-4-11 memory is DDR888* (i)
5-2-2-18(!) memory doesn't seem that useful (g), but perhaps (f) ok? (i)
was an attempt at a balanced solution - seems good
comparing (e) and (g), 4-4-4-11 v 5-2-2-11 is ~4%

strange bug in (h)/(i) - memtest or mobo wrong?
if memtest correct, (i) and (d) memory limit between DDR888* and DDR923*
otherwise (m) has fast memory

try:
350MHz, DDR750, 4-4-4-11 (pushing i/f)
346MHz, DDR922*, Auto (f)
350MHz, DDR933*, Auto (pushing f)
333MHz, DDR888*, 4-4-4-11, higher V? (retry h)


100307 - all standard voltages except (p)

o  2.80GHz   350MHz  DDR700   4-4-4-11  fail
p  2.80GHz   350MHz  DDR700   4-4-4-11  fail  FSB 1.3V
q  2.66GHz   333MHz  DDR888*  4-4-4-11  fail (confirm above)
r  2.66GHz   333MHz  DDR833!  4-4-4-11  fail
s  2.66GHz   333MHz  DDR711!  4-4-4-11  fail
t  2.13GHz   266MHz  DDR889!  4-4-4-11  fail
u  2.13GHz   266MHz  DDR771!  4-4-4-11  fail

v  2.72GHz   340MHz  DDR680   4-4-4-11  new best candidate?
             340MHz  DDR906   4-4-4-11

w  2.77GHz   346MHz  DDR923*  5-5-5-15  fail
x  2.77GHz   346MHz  DDR923*  5-2-2-18  fail

y  2.77GHz   30%     Auto     Auto
             346MHz  DDR692   5-2-2-18

z  2.77GHz   346MHz  Auto     Auto
             346MHz  DDR692   5-2-2-18

-  2.77GHz   346MHz  DDR865*  Auto      fail (hard)
=  2.77GHz   346MHz  DDR692   4-4-4-11  fail (in memtest)
_  2.77GHz   346MHz  DDR692   5-2-2-18  fail

f  2.77GHz   346MHz  DDR692   Auto      previous (f) must have had error
             346MHz  DDR922*  5-2-2-18

e  2.77GHz   346MHz  Auto     4-4-4-11  equivalent to (e above)
             346MHz  DDR692   4-4-4-11

$  2.66GHz   333MHz  DDR666   Auto      doesn't give (i)
             333MHz  DDR888*  5-2-2-11

so after all that we have three candidates.
all odd - need auto and/or conflict between bios and memtest

e  2.77GHz   346MHz  Auto     4-4-4-11
             346MHz  DDR692   4-4-4-11

f  2.77GHz   346MHz  DDR692   Auto
             346MHz  DDR922*  5-2-2-18

i  2.66GHz   333MHz  DDR666   4-4-4-11
             333MHz  DDR888*  4-4-4-11

note that none can be specified exactly:

=  2.77GHz   346MHz  DDR692   4-4-4-11  fail (in memtest)
_  2.77GHz   346MHz  DDR692   5-2-2-18  fail
i  is specified exactly, but measures differently

kernel compile times (while rebuilding raid):

e  17m45s (33m/4m)
f  17m20s (31m/3m)
i  18m06s (34m/3m)
n  22m18s (39m/4m)

normalising all results:

f  2.77GHz 346MHz DDR922 5-2-2-18  0.78        +28%
i  2.66GHz 333MHz DDR888 4-4-4-11  0.79, 0.81  +23-27%
e  2.77GHz 346MHz DDR692 4-4-4-11  0.80, 0.80  +25%
g  2.77GHz 346MHz DDR692 5-2-2-18  0.83        +20%
n  2.13GHz 266MHz DDR712 4-4-4-11  1.00

difficult to improve further because nothing fixed exactly.
cannot "push" auto value.  don't want to play with voltages.