Difference between the WD1771 and wd1770,2, and 3

I've been reading over the datasheets for these four chips and have come across a difference. On the WD1771: During the verify stage of a type 1 command, it will only check the track number against the first ID record it finds. If the ID record has a CRC error, it will set the CRC status bit and set the INTRQ. If the Track field doesn't match the Track register, it will set the seek error status bit and set the INTRQ. Otherwise it will just set the INTRQ. It will not go looking for another IDAM. The WD1770, WD1772, and WD1773 search through five revolutions of the disk until it finds an ID record with the correct track value and a correct CRC value. Since I only have 1773s in my collection I can't test if the 1771 actually behaves this way. Does anyone know if the datasheets are correct in this case? Also, does anyone know how long the index pulse lasts for 8", 5.25" and 3.5" disk drives? -- tim lindner tlindner(a)ix.netcom.com Bright