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Memory Characteristics

Tight Timings vs High Clock Frequencies

The following table shows the two most popular types of system memory chips for enthusiast systems, and their typical specifications:

Popular Enthusiast Memory Types
Memory chips Timings Clock frequencies Voltage
Winbond BH-5/BH-6/UTT CL1.5 or 2.0-2-2-5 400-500 MHz 2.5 - 3.8 V
Samsung TCC5/TCCD CL1.5 or 2.0-2-2-5

CL2.5 or 3.0-4-4-7/8

400 MHz

500-600 MHz

2.5 - 2.9 or 3.0 V

As you can see, there are some differences between system memories depending on which chips are used. Samsung TCC5/TCCD could be described as flexible when compared to the Winbond chips, as they will work at low clock frequencies and tight timings, as well as at high clock frequencies and more relaxed timings. However, Winbond chips will reach higher clock frequencies than Samsung chips if you are dead set on using 2.0-2-2-5 timings; this assumes that you have a motherboard capable of supplying them with the voltage they need.

In practice, you might see 2x 512 MB Winbond memory reaching 250 MHz or as high as 270 MHz at CL2.0-2-2-5 timings, while 2x 512 MB Samsung memory might reach 300 or slightly more at CL2.5-4-3-7, CL2.5-4-4-8 or CL3.0-4-4-8.

Test Memory: G.Skill F1-4400DSU2-1 GBFC

Since we are comparing the relative impact of latency and clock frequency increases, we decided to use memory based on Samsung's TCC5/TCCD. This memory will allow us to use a wider range of settings.

Taiwanese memory maker G.Skill supplied us with two 512 MB sticks of its fairly new F1-4400DSU2-1 GBFC product. It is rated at PC4400 (DDR550) and CL2.5-4-4-8 timings, and is the company's attempt to bring enthusiast performance and overclocking to the mainstream market.

Performance will obviously vary from module to module, and will also depend on the motherboard, BIOS version, BIOS settings and CPU used. In our case, stable operation was possible in the range from 2.0-2-2-6 at 203 MHz to 2.5-4-3-7 at 300 MHz.

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