buck@siswat.UUCP (A. Lester Buck) (03/27/90)
I have had some problems installing 386/ix on a PS/2 Model 80 with 70 MB ESDI disk. IBM documentation lists this disk as having 36 sectors/track, 7 heads, and 583 cylinders. After a complete low level format and defect scan, using the advanced diagnostics on the reference diskette (control-A mode), the disk is reported to have 36 sectors/track, 7 heads, and 569 cylinders with zero defects found. (I don't know what the extra 14 cylinders are reserved for.) The 386/ix boot disk reports the disk configuration as 32 sectors/track, 64 heads, and 70 cylinders. The installation disk is able to change ONLY the cylinders parameter. Clearly some type of mapping is occurring inside 386/ix. Since the actual number of sectors (36*7*583 = 146916) is less than the remapped number (32*64*70 = 143360), things should work out if the mapping is consistent. But the complete bad sector scan in 386/ix always bombs out at the end of the disk, reporting the disk as unusable. Apparently, the disk is treated as really having only 32 sectors/track, and the actual number of sectors (7*583 = 4081) is less than the remapped number of sectors (64*70 = 4480). I successfully installed by backing down the number of cylinders from 70 to 63 (64*63 = 4032 < 4081). What is the point of this remapping scheme? The net effect is to discard (36-32)/36 = 11% of usable disk space. Why can't 386/ix read the disk geometry from the ESDI interface, like any other ESDI interface? And if 386/ix is going to remap the disk geometry, how about doing the calculation correctly? -- A. Lester Buck buck@siswat.lonestar.org ...!texbell!moray!siswat!buck