Author: Greg Lindahl
Date: 17:00:05 12/22/99
Go up one level in this thread
On December 22, 1999 at 11:19:34, Magnus Homann wrote: >And how long does it take to read the data back? You'll get about 1-10 MB/s on >the PCI bus, unless you watch out a bit. It takes 1 usec to grab the bus, and then you can transfer either way. Since the return value is tiny, the answer is: 1 usec. For a graph of bandwidth vs. size of transfer, see: http://www.myri.com/myrinet/performance/DMAperf.html That page doesn't have any numbers for any Alpha 21264 systems, which are substantially better. >Really? So how much data do you typically move? Well, Vincent says he needs 160 bytes for one eval. You might move N times this at once. So, an average answer from the page above is ~ 10 MB/s for 160 byte transfers, and > 50 MB/s for 1600 byte transfers. > So far, I have no clue what you expect the FPGA to do. Neither do I, as I've said repeatedly. However, if you want to know the impact of the PCI bus on a design, it's well known. That was my only point in this little sub-thread. -- g
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