bloodline wrote:
I can only think he is referring to the old southbridge DMA... I guess he doesn't know that it's not used any more, since DMA is an old concept... with USB, FIrewire and PCI-E
Wow. just Wow.
I hope you didn't mean that the way you typed it.
I should probably let Nate answer this himself, as I'll probably get it as wrong as you did. Yes, DMA is old. It's as old as the IBM System 360, and it's as old as the Nvidia GTX 280.
DMA stands for Direct Memory Access. It's not (just) a theoretical concept, or an antique type of data bus, it's a data transfer method, regardless of bus. It's the method a peripheral device uses to put/get its data into/from memory without getting permission from the CPU. It's written into the PCI/AGP/PCI-e specs.
An nVidia SLI setup uses DMA. It doesn't wait for the CPU to fill its (3-way) 3 Gigabytes of texture/data RAM, the CPU tells the GPU where in main memory the data is, and the GPU goes and gets it, itself. If you have a network connector, it will also DMA its data, as will any SCSI, and most SATA and PATA controllers (hint: U
DMA mode).
BTW, Firewire, aka IEEE-1394, aka Sony iLink, also uses DMA.
DMA is also the reason there's a patch for A1-XEs. If the OS isn't critically careful, the peripheral DMA data can get overwritten by the CPU - while the DMA transfer is still in progress.
