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AR# 45848

Kintex-7 FPGA KC705 Base TRD - Issues with DMA performance


The DMA performance on the Kintex-7 FPGA KC705 Base TRD is not stable and is lower than expected. Why is this, and how can this be fixed?


On some Intel x58 chipsets, the DMA performance on the Base TRD fluctuates and is lower than expected. This is believed to be due to intel-iommu having issues freeing up DMA page tables.

This issue can be resolved as follows:

When Fedora 16 Live is booting
i. Press tab for full configuration options on menu items.
ii. Add iommu=pt64 at the end of the line vmlinuz0 initrd=initrd0 ...rd.md=0 rd.dm=0
iii. Hit the enter key to boot with this option.
AR# 45848
Date Created 02/13/2012
Last Updated 02/27/2012
Status Active
Type Known Issues