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21020285 D User’s Guide
Appendix E Design Differences
Page E - 6 How to Maximize Performance
Uniquely Identify the RF3880
In order to differentiate the RF3880 from the RF3560/70 and RF3870, a new
word field was added to the Board Information Data Structure returned from
the Board Information command. This new word is the Adapter Base Model #
(number) word.
Odd-byte Addressing
VME addresses for transfers must be word-aligned.
How to
Maximize
Performance
In order to take full advantage of the RF3880 design, you should do the
following:
• Align VME D64 data buffers to 2K address boundaries, and specify a
Bus Throttle of 2048 bytes per burst. Any other alignment will reduce the
maximum Burst size to 256 bytes per burst.
• Align all data buffers to double-longword address boundaries. Any other
alignment will cause multiple data transfer cycles on the VME bus. The
first transfer will move enough data to align the address to a double-
longword. The next transfer will move the data according to the Bus
Throttle setting.