Saturday, August 14, 2010

High density RAM

In the context of the 1 GB non-ECC PC3200 SDRAM module, there is very little visually to differentiate low density from high density RAM. High density DDR RAM modules will, like their low density counterparts, usually be double-sided with eight 512 Mbit chips per side. The difference is that for each chip, instead of being organized in a 64M×8 configuration, it is organized with 128 Mbits and a data width of 4 bits, or 128M×4. To further confuse the issue, some RAM is labeled as 128M×8, and is also called high density.

Most high density PC3200 modules are assembled using Samsung chips. These chips come in both the familiar 22 × 10 mm (approx.) TSOP2 and smaller squarer 12 × 9 mm (approx.) FBGA package sizes. High density Samsung chips can be identified by the numbers on each chip. If the sixth and seventh characters are 04 (for example K4H510438D-UCCC) then the chips are ×4 and high density. If the sixth and seventh characters are 08 then the chips are ×8 and low density.

High density RAM devices were designed to be used in registered memory modules for servers. JEDEC standards do not apply to high-density DDR RAM in desktop implementations. JEDEC's technical documentation, however, supports 128M×4 semiconductors as such that contradicts 128×4 being classified as high density. As such, high density is a relative term, which can be used to describe memory which is not supported by a particular motherboard's memory controller.

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