Sure 2 gigabytes of memory has been the standard for a while now, but today's software has been gradually upping the anti to 4 gigabytes over the last year.  Led by windows Vista, the demand for high performance DDR2 in 4 GB kits keeps getting hotter.  The trouble is, there just isn't much memory in the 4 GB kits worth getting exited about.  Mushkin is about to change that with several 4 GB additions to their performance DDR2 lineup.

     Today we will be looking at their XP2-6400 DDR2 Kit, just one of the several new 4 GB kits available.  Featuring low latencies and double the space we have become used to, this may be the 4 GB upgrade you have been looking for.  Take a look right here at the Club.

 Specifications:

• 2 x 2GB (4GB KIT) Memory Modules
• Voltage:  DDR2-6400 at 2.0-2.1V
• Latency: 4-4-4-12
• Frequency: 800 MHz
• Parity: Unbuffered
• 240-Pin Dual Inline Memory Module (DIMM) with gold contacts
• Density: Module: 256Mx64, Chip: 128x8
• Frostbyte Advanced Heatsinks
• Fitting in industry standard motherboards

     The actual modules are very attractively put together.  Each module is jacketed with an attractive Frostbyte Advanced heatsink design held in place by two clips.  The heatsinks hide a more mundane green board and the Mushkin branded chips.

Description:

To quote Wikipedia:

     "Like all SDRAM implementations, DDR2 stores memory in memory cells that are activated with the use of a clock signal to synchronize their operation with an external data bus. Like DDR before it, DDR2 cells transfer data both on the rising and falling edge of the clock (a technique called "dual pumping"). The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so four words of data can be transferred per memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR.

DDR2's bus frequency is boosted by electrical interface improvements, on-die termination, prefetch buffers and off-chip drivers. However, latency is greatly increased as a trade-off. The DDR2 prefetch buffer is 4 bits deep, whereas it is 2 bits deep for DDR and 8 bits deep for DDR3. While DDR SDRAM has typical read latencies of between 2 and 3 bus cycles, DDR2 may have read latencies between 4 and 6 cycles. Thus, DDR2 memory must be operated at twice the bus speed to achieve the same latency.

Another cost of the increased speed is the requirement that the chips are packaged in a more expensive and more difficult to assemble BGA package as compared to the TSSOP package of the previous memory generations such as DDR and SDRAM. This packaging change was necessary to maintain signal integrity at higher speeds.

Power savings are achieved primarily due to an improved manufacturing process through die shrinkage, resulting in a drop in operating voltage (1.8 V compared to DDR's 2.5 V). The lower memory clock frequency may also enable power reductions in applications that do not require the highest available speed."

     The label clearly states the CAS 4-4-4-12 timings at 2T as well as the recommended voltage ratings of 2.0 to 2.1Volts.  I found the memory defaulted to lower 5-5-5-18 latencies at the default 1.5V and refused to boot with the correct latencies until I upped the voltage to 2.0.