re ide vs scsi on mon apr gmt wayne smith wlsmith valve heart rri uwo ca wrote in article richk apr gozer grebyn com richk grebyn com richard krehbiel writes so when you ve got multi tasking you want to increase performance by increasing the amount of overlapping you do one way is with dma or bus mastering either of these make it possible for i o devices to move their data into and out of memory without interrupting the cpu the alternative is for the cpu to move the data there are several scsi interface cards that allow dma and bus mastering how do you do bus mastering on the isa bus as an earlier post noted through dma ide however is defined by the standard at interface created for the ibm pc at which requires the cpu to move all the data bytes with no dma if we re talking isa at bus here then you can only have dma channel active at any one time presumably transferring data from a single device so even though you can have at least devices on a scsi bus explain how all of those devices can to dma transfers through a single scsi card to the isa at bus at the same time any one time means imho a single byte xfer if i have four sources of dma requests ready the dma would service the one after the other if the bandwidth for the four together is lower than the isa dma bandwidth this will work note that the bus mastering here is the priority mechanism in the dma controller penio penev x w internet penev venezia rockefeller edu disclaimer all oppinions are mine
