max DMA transfer rate

[Neil.Pate]

Does anyone have any real-world numbers for maximum DMA transfer rate from host to PC?

Assuming fast enough PC, and PXI-7952 FlexRIO board (connected via a fibre PXI bridge), I am looking to continuously transfer approximately 105 Mbits/second from target to the host. Is this achievable (using DMA transfers)?

[HSTech]

A couple quick questions for you:

1. Just to make sure we are on the same page... 105 Mbits/second =  13.125MBytes/second. 

2. Is the fibre PXI bridge an NI product or something from a third party?

PCI is capable of a theoretical 133 MBytes/second transfer rate.  Given bus overhead, the NI ASIC technology gives us about ~100 - ~102MBytes per second of peak transfer rates.  So assuming a good computer, 13.125 MBytes should be well within the bus and 7952 capabilities.

But as I am sure you know, PCI is a shared bus - so your 7952 has to share that bandwidth with other devices that might be using the bus - both in the PXI chassis and in the computer to which it is attached.

If bandwidth is a concern for you, you could also consider the new PXIe-7961 or 7962.  These are new FlexRIO boards based on PXI Express that can achieve sustained rates in excess of 750MB/s from the card to the computer in addition to ~700MB/s from the computer to the card.  

[Neil.Pate]

hi HSTech

Thanks for the info.

Yes, I am looking at about 104 Mbits/s so this should be well within the limits of the PCI transfer rate. The PXI bridge is an NI part.

Now I just have to figure out how to get 8 lines of data clocked at 250 MHz into LVFPGA!

Then I have to figure out how to get the serial data packed into 12-bit words correctly,

Then I have to figure out how to sustainably write 13 MB/s onto the hard disk.

At least the last one is easy, buy a RAID array if all else fails 🙂