neese@adaptx1.UUCP (11/03/90)
>/* ---------- "BIOS overhead on Adaptec SCSI HD ac" ---------- */ >I got the Norton Utilities 5.0 the other day, and ran Calibrate on my hard >drive, which I've never felt performed as well as it should. Calibrate told >me that I have 33ms of BIOS overhead on top of my drive's 28ms access time. >This seems ridiculous to me; any comments? I don't really know what Calibrate is doing to determine the overhead, but it is absolutely not 33ms. If it is using the BIOS translation table of 64 heads, 32 sectors in some INT 13 call which causes any disk activity, the program is worthless, in this scenario. SCSI drives do not have a physical interface. It is a logical block interface. The 154x BIOS fakes out DOS by using 64 heads, 32 sectors per track an figuring out the number of cylinders based on the data returned from the read capacity command. Bottom line: There are absolutely no programs that use INT 13 that can accurately measure SCSI disk performance. Because I have had to answer this time and time again, it has prompted me to start writting a benchmark for DOS, that can be used to intelligently calculate disk performance of a SCSI disk, under DOS, at the BIOS level. Just give me a little time. Roy Neese Adaptec Senior SCSI Applications Engineer UUCP @ uunet!utacfd!cs.utexas.edu! {nominil,merch,cpe}!adaptex!neese uunet!mlite!adaptex!neese