On Sat, Jul 26, 2008 at 1:40 PM, Petri Helenius <petri@helenius.fi> wrote:
William Herrin wrote:
But cards like the Intel Pro/1000 have 64k of memory for buffering packets, both in and out. Few have very much more than 64k. 64k means 32k to tx and 32k to rx. Means you darn well better generate an interrupt when you get near 16k so that you don't fill the buffer before the 16k you generated the interrupt for has been cleared. Means you're generating an interrupt at least for every 10 or so 1500 byte packets.
This is not true in the bus master dma mode how the cards are usually used. The mentioned memory is used only as temporary storage until the card can DMA the data into the buffers in main memory. Most Pro/1000 cards have buffering capability up to 4096 frames.
Pete, I'll confess to some ignorance here. We're at the edge of my skill set. The pro/1000 does not need to generate an interrupt in order to start a DMA transfer? Can you refer me to some documents which explain in detail how a card on the bus sets up a DMA transfer? Thanks, Bill -- William D. Herrin ................ herrin@dirtside.com bill@herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004