Network cards use several technique for DMA interrupt mitigation. When sending data to the card. The command steam is usually located in on card memory to reduce bus access. A the end of the stream you place a special op code that causes the GPU to slowly loop on that opcode. Slow is a relative term. When you are ready to run more commands you use the shared memory interface to alter the opcode. The copy is usually one word so that it can be altered atomically. This allows you to add more command where or not the GPU has reached the special opcode. This eliminates the need for an end of stream interrupt. In this model GPU input command stream processing is never truly halted.
When transferring data off the card newer network cards have a programmable interrupt mask. The idea is that at the end of the CPU processing each packet it resets the timer and checks to see if another packet is waiting. This allows you to receiver many packets at high speed without generating an interrupt. When the packets stop coming you won't have reset the interrupt mask and the next packet will generate an interrupt. As for page flipping, the ATI cards can be programmed to automatically flip on each vertical retrace. You can use this to eliminate the need for retrace interrupts. -- Jon Smirl [EMAIL PROTECTED] _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
