Bus Bandwidth Measurements?

[steve13]

I'm helping a friend with a report but I can't answer a question about bus bandwidth. By my calculation an 800 MHz bus (like Intel quadrupal-pumped 200 MHz) with a 64-bit width should transfer 6.400,000,000 bytes (512,000,000,000 bits) per second. I've always read that the bus transfers 6.4 GB/s, however, but 6.4 GB = 6871947673.6 bytes if a GB = 1073741824 (2^30). The 800 MHz but should then transfer about 5.96 GB/s instead, right?

My assumption is that when measuring bus bandwidth a GB = 1,000,000,000 bytes (not 2^30 bytes) which would make the 6,400,000,000 Bytes = 6.4 GB exactly.

Could someone please clear this up?

Thanks

 

[Cattlegod]

This isn't really Hightly Technical. I think you are simply confusing bits with bytes.

 

[itachi]

Originally posted by: Cattlegod
This isn't really Hightly Technical. I think you are simply confusing bits with bytes.

:thumbsup:

f = 800 MHz; w = 64-bits = 8 bytes
f * w = 6,400 MB/s = 6,400 MB / 1024 MB GB/s = 6.25 GB/s = 6,400 * 2^20 bytes/s = 6,710,886,400 bytes/s.
f * w = 51,200 Mb/s = 50 Gb/s
50 Gbps * B/8b = 6.25 GB/s