dont@tekig1.UUCP (02/26/84)
With the advent of track buffering, we get a big improvement in performance, we no longer need wait half a revolution for each sector. But, we wait half a revolution for the track, when there is good material going by all that time. The floppy disk controllers ICs are smart enough to do multisector reads, with- out processor intervention, but all I have seen demand the starting sector be identified, and matched before the transfer begin. Have I missed a controller that can start transfers on the next available sector, or has someone found a way to fool a controller into doing this sort of thing? I'm hoping to find one that can take advantage of DMA control, double density, 8" disks, and buffering. Many thanks in advance. Don Taylor
mzp@uicsg.UUCP (02/27/84)
#R:tekig1:-154800:uicsg:7600013:000:1320 uicsg!mzp Feb 26 18:24:00 1984 <--------------------------> Whale, one thing you can do (speaking with WD2793 experience) is to issue a read-address command. This waits for the next ID field and chunks back six bytes indicating the track, sector, side, size, and CRC. You can use this information to intelligently generate a request for the sector following that one. This is just ad hoc thought, by the way. I don't know of any software that actually takes advantage of this capability. I am personally too lazy to write the drivers required to do track buffering, much less anything this complicated. As for intelligent controllers, the WD2790 series are the best that I have come across. They have a built-in PLL data seperator for DD and support 5"/8" drives. I have built a 4-disk 8" controller for an 8086 system that takes about 10 square inches of board space! This of course presupposes an existing DMA device. DMA transfers are supported by the 279x. The NEC765/i8272 have some nice features, including a bit more programmability and built-in 4-drive select and head load, but the Western Digital controllers are unquestionably easier to use. Hope that this at least provides you with a start in the right direction. Let me know if you come across anything exciting. Mark Papamarcos pur-ee!uiucdcs!uicsl!uicsg!mzp