what is the REAL difference between.....

.....Kingston KVR400X72C3A/512 & KVR400C64C3A/512?

something to do with x72 and the c64. Its Kingston Value Ram pc 3200, 512mb. If I can find out more I'll post

found it the first is 72 bit, and the second is 64 bit. or in other words 64 bit is Non ECC, whereas the extra 8 bits in the 72 is for error correction

What is the difference between 72 bit and 64 bit memory?
What is the difference between 32 bit and 36 bit memory?

72 bit memory is commonly known as ECC memory. It has an additional 8 bits for Error Correction Check 64 bit memory is non-ECC. 72 bit or 64 bit
configuration are typically found in 168 pin DIMMs

36 bit memory is commonly known as parity memory. It has an additional 4 bits for parity checking. 32 bit memory is non-parity. 32 bit or 36 bit configuration are typically found in 72pin or 30 pin SIMMs


from http://www.ddrmemoryupgrades.com/memory_questions.html

Thank you. Now I know.