ARM Technical Support Knowledge Articles

Does using the ARM720T FASTBUS mode give significant performance improvement?

Applies to: ARM720T


No. The FASTBUS mode of operation will typically be slightly slower than running in synchronous mode with BCLK=FCLK. Fastbus mode works by internally generating FCLK by inverting BCLK. It will then internally synchronize backward & forward between the 2 clocks depending upon whether or not it is performing an external access (i.e just as it would do when not in FASTBUS mode). As FCLK is just inverted BCLK, there is always a full clock phase for synchronization and so your code runs slower than it would do in the non-FASTBUS case. Running with BCLK = FCLK violates the device's clock timing requirements - we don't guarantee this works except at slow clock speeds.

Article last edited on: 2008-09-09 15:47:37

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