Sign in with
Sign up | Sign in

Boosting Memory Clock Speed: 23% Performance Gains

In Search of True DDR2 Bleeding Edge Memory
By

On the other hand, boosting memory clock rate by itself can produce significant performance gains. As before, we used the outstanding Corsair CM2X512-8000UL Corsair memory modules for the memory clock speed and latency analysis below.

The clock rates for DDR2-400 up to DDR2-800 were analyzed in tandem with FSB speeds of 800 and 1066. The reference point for our analysis is DDR2-533 RAM, because this is the type most frequently-installed in commercial PCs. That’s because DDR2-400 is neither very prevalent nor very widely used.

Speed analysis with an FSB speed of 800 :

Module Clock Speed (CL 5.0-5-5-15) FSB800 (200 MHz)

FSB800 (200 MHz)

Read

Write

Latency

DDR2-800 (400 MHz)

6189 MB/sec

2142 MB/sec

82.9 ns

DDR2-667 (333 MHz)

6105 MB/sec

1985 MB/sec

88.0 ns

DDR2-600 (300 MHz)

6052 MB/sec

1890 MB/sec

88.1 ns

DDR2-533 (266 MHz)

6024 MB/sec

1743 MB/sec

89.5 ns

DDR2-400 (200 MHz)

5464 MB/sec

1389 MB/sec

111.4 ns FSB800 (200 MHz)

Read

Write

Latency

DDR2-800 (400 MHz)

102.7%

122.9%

108.0%

DDR2-667 (333 MHz)

101.3%

113.9%

101.7%

DDR2-600 (300 MHz)

100.5%

108.4%

101.6%

DDR2-533 (266 MHz)

100.0%

100.0%

100.0%

DDR2-400 (200 MHz)

90.7%

79.7%

80.3%

This table shows clearly what we measured in our labs at THG : if a DDR2-800 memory module is used with an FSB speed of 800, it can boost memory read access by 2.7% and write access by 22.9%. The latency timing in our measurement improves by about 8%. From these results we draw the following conclusion : Those who don’t boost FSB speeds won’t realize any significant performance improvements simply from faster memory clock speeds.

A speed analysis with an FSB speed of 1066 :

Module Clock Speed (CL 5.0-5-5-15) FSB1066 (266 MHz)

FSB800 (200 MHz)

Read

Write

Latency

DDR2-888 (444 MHz)

7819 MB/sec

2554 MB/sec

73.9 ns

DDR2-800 (400 MHz)

7748 MB/sec

2431 MB/sec

75.6 ns

DDR2-711 (355 MHz)

7673 MB/sec

2258 MB/sec

76.3 ns

DDR2-667 (333 MHz)

7310 MB/sec

2110 MB/sec

83.6 ns

DDR2-533 (266 MHz)

7066 MB/sec

1822 MB/sec

86.3 ns

DDR2-400 (200 MHz)

5732 MB/sec

1458 MB/sec

105.2 ns FSB800 (200 MHz)

Read

Write

Latency

DDR2-888 (444 MHz)

110.7%

140.2%

116.8%

DDR2-800 (400 MHz)

109.7%

133.4%

114.2%

DDR2-711 (355 MHz)

108.6%

123.9%

113.1%

DDR2-667 (333 MHz)

103.5%

115.8%

103.2%

DDR2-533 (266 MHz)

100.0%

100.0%

100.0%

DDR2-400 (200 MHz)

81.1%

80.0%

82.0%

This table reflects our test series and documents some impressive results. With an FSB speed of 1066 (266 MHz), a switch to DDR2-888 finally starts to pay off. Read access times then improve by 10.7% and write access times by 40.2%. At 16.2%, the speed boost for latency is double that for an FSB 800 system. This doesn’t demonstrate anything startling, however : the bottleneck in a DDR2 Intel platform has been and remains the front side bus (FSB).

React To This Article