Crucial 2GB (2x 1GB) DDR2-800 PC2-6400 1.8V SR x8 240-pin UDIMM RAM Kit Capacity_8GB but the effective rate is

but the effective rate is 667 megatransfers per second (MT/s) because there are 333 million rising edges per second and 333 million falling edges per second of a clock signal running at 333 MHz

This 512MB (1x 512MB) DDR2 533 MT/s

x8 configuration RAM kit from Kingston is for use in DDR2 compatible systems and operates at 533 MT/s with an overall transfer rate of PC2-4200

KVR533D2N4K2_1G Capacity 1GB (2x 512MB) Brand Kingston Speed DDR2-533 - 533MT/s - PC2-4200 Voltage 1

2xCT12864AA800 Capacity 2GB (2x 1GB) Brand Crucial Speed DDR2-800 - 800MT/s - PC2-6400 Voltage 1

Crucial 2GB (2x 1GB) DDR2-800 PC2-6400 1.8V SR x8 240-pin UDIMM RAM Kit Capacity_8GB but the effective rate isProduct Overview This 2GB (2x 1GB) DDR2 800 MT s Single rank, x8 configuration RAM kit from Crucial is for use in DDR2 compatible systems and operates at 800 MT s with an overall transfer rate of PC2 6400. This RAM kit also operates at a standard voltage of 1. 8V and is designed to allow you to run more applications simultaneously, switch between them faster, and provide a smoother computing experience. Technical Specifications Part No. 2xCT12864AA800