phil@pepsi.amd.com (Phil Ngai) (06/13/90)
In article <452@hitachi.uucp> jon@hitachi.UUCP (Jon Ryshpan) writes: |I don't think so. In the AT the data has to go from the peripheral to |the DMA chip and then out of the DMA chip into memory. Very often the Sorry, this is not correct. PC DMA is actually clever in some ways. The DMA transfer is quite efficient in design, using "flyby" cycles where the source (IO or memory) puts the data on the bus and the receiver (memory or IO, must be the opposite of the source) takes the data off the bus in the same cycle. The big problem is that the DMA controller runs so slower that indeed the CPU can often transfer data faster. -- Phil Ngai, phil@amd.com {uunet,decwrl,ucbvax}!amdcad!phil