PC3200 is DDR SDRAM designed to operate at 200 MHz using DDR-400 chips with a bandwidth of 3,200 MB/s. As the memory is double pumped, this means that the effective clock rate of PC3200 memory is 400 MHz.
1 GB PC3200 non-ECC modules are usually made with sixteen 512 Mbit chips, 8 down each side (512 Mbits × 16 chips) / (8 bits (per byte)) = 1,024 MB. The individual chips making up a 1 GB memory module are usually organized with 64 Mbits and a data width of 8 bits for each chip, commonly expressed as 64M×8. Memory manufactured in this way is low density RAM and will usually be compatible with any motherboard specifying PC3200 DDR-400 memory.