What is the realistic data transfer rate over a 32-bit/33MHz PCI bus? We need to transfer 32K 32-bit samples from a PCI card to an Intel CPU running Windows. I would think the block would transfer in 1msec but it is taking 40msec. The PCI board has a PLX PCI-9056. We are accessing card memory with a virtual address, but our CPU is bricked-out which make me think the data rate is being held up by CPU involvement. If we go to DMA, will we transfer in closer to 1msec? The reason I have my doubts is the PXI SDK User Manual states:
"BAR space memory read/write is generally slow in relative terms. Reads are typically only 2-4MB/s."
You should check if you can enable burst mode and continuous burst, such that multiple DWords can be transmitted without new address cycles. This makes things much faster. The PLX PCI9056 supports this option, but it must be set by SW accordingly. We have data rates up to 90 MB/s with DMA Master Transfer on our custom designed frame grabber card.