SBus-DMA Performance

SUN SBus allows data to be directly DMA transferred between host main-memory and adaptor on-board RAMs.

Performance

• Configuration: Sun SPARC 20/71 (SUNOS), Myrinet SBus adaptor 2.3
• L2H: from on-baord RAM to host memory
• H2L: from host memory to on-board RAM
• L2L: between on-board RAMs of two separate units
• Testing software
• Tabulated performance results

Observation:

• The sustained host-to-board bandwidth is lower than SBus spec.
• The board-to-board bandwidth does not exceed 100 Mbps because Myrinet adaptor does not supported SBus slave burst-mode.
• A Myrinet adaptor has to be SBus-DMA master in order to achieve high throughput (over 100 Mbps) board-to-board DMA between the Myrinet board and a non-Myrinet board (e.g. FORE System SBA-200).

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Last modified Oct 23, 1995.