Core 2 Duo CPU fluctuation

[wowen]

I'm doing a hardware evaluation and part of that is using Passmark Performance Test to score the hardware.
All of the machines have Intel Core 2 Duo processors in them and almost all of them are showing a wide range in CPU mark scores.

Here is the CPU Mark from 100 iterations of CPU tests on an Intel Core 2 Duo 2.66ghz machine (sorted low to high):
CPU Mark 1734 1750.5 1765.1 1766.3 1767.4 1777.4 1784.1 1785.6 1786 1787.8 1789.5 1795 1795.7 1796.9 1800.7 1801.7 1805.9 1808.3 1810.9 1816.2 1820.1 1825.6 1827.9 1829.2 1831.3 1834.6 1843.6 1844.4 1845.9 1861.3 1868.8 1880.4 1881.2 1884.9 1886.1 1890.9 1895.4 1905.1 1906.8 1911 1913 1915.9 1916.9 1922.8 1925.5 1926.1 1927.5 1930.9 1933.2 1933.2 1934.8 1935.4 1936.1 1936.1 1946.3 1949.7 1958 1959.4 1961.8 1961.9 1964 1965.7 1966.3 1967 1968 1975.2 1975.2 1981.2 1981.3 1984.7 1992.6 1994.1 1994.2 2002.3 2003.8 2007.9 2011.9 2017.4 2023 2032 2040.6 2041.1 2043.2 2066.6 2069.4 2070.3 2099.6 2106.5 2111.3 2118.6 2131.1 2159.7 2171 2199.6 2220 2348.7 2375.9 2403 2479.6 2533.6
And now the same for a Core 2 Duo 2.40ghz:
CPU Mark 1482.7 1490.6 1493.4 1494.1 1498.5 1499.8 1501.8 1505.2 1513.7 1518.6 1520.6 1523.7 1525.3 1525.3 1529.6 1533.9 1534.1 1534.2 1536.6 1537.7 1540.5 1544.7 1553.5 1555.6 1559 1566.8 1575.6 1576.7 1589.7 1590.7 1607.2 1609.8 1615.9 1617.7 1618.1 1630.7 1649.3 1657.9 1682.3 1686.8 1692.6 1693.4 1718 1728.4 1731.5 1741.2 1743.6 1747.2 1747.5 1755.3 1766.2 1787.5 1795.8 1798 1800.2 1802.4 1818.8 1827 1831 1838.7 1846.7 1854.8 1872.6 1876.7 1905.4 1914.4 1926.8 1936.4 1981.3 1993 1999.7 2008.7 2020.2 2020.9 2023.3 2028 2044.5 2046.2 2051.8 2057.8 2073.2 2080 2081.6 2115.3 2126.2 2133.7 2147.2 2153.9 2181.1 2187 2194 2197.7 2212.4 2214.6 2261.4 2274.8 2290.8 2295.7 2472.8 2545.6
Those ranges look awfully wide. It seems that a number of the CPU tests show spikes that contribute to these score fluctuations but nothing consistent.
Is this a known issue with these processors?

[David (PassMark)]

There is no issue that we are aware of. Do you know exact what model CPUs you are using? Was it for example Core2 Duo E8200 @ 2.66GHz or Core2 6700 @ 2.66GHz

The ranges you have are more than expected. 5% - 10% would be more typical. This might be something to do with your test method, or it might be that you have some other tasks running occasionally in the background, or it might be something else, like the CPU overheating and throttling down some of the time.

[wowen]

testing process

We're testing two different CPUs, a Dell 755 Optiplex with an Intel E6750, 2.66, 4MB, CORE DUO-CONROE.
And an HP dc5800 E6750, E4600 @ 2.40GHz

That we are seeing this fluctuation with BOTH processors suggest that we have something running in the background? They both have our "standard" image installed (WinXP SP2 + common applications like Office and other company-wide apps) so it is likely that a service or process causing this would be running on both machines.

The testing process has just been to disable the virus scanner, make sure no other programs are running, and let the PassMark Performance test loop through the CPU Mark tests 100 times. Even with the fluctuations, I think we are getting a reasonable report by taking the average.