HP 3.5 discs I wonder if in the HP 150 manual? Back when we sold the things .... I still have a maint manual for the 150... offlist mail me if you still have questions and I will dig it up. Ed Sharpe archivist for SMECC www.smecc.org In a message dated 2/1/2013 10:25:55 A.M. Mountain Standard Time, cctalk-request at classiccmp.org writes: Message: 5 Date: Thu, 31 Jan 2013 21:50:14 +0000 (GMT) From: ard at p850ug1.demon.co.uk (Tony Duell) To: cctalk at classiccmp.org Subject: Re: Looking for Appendix to HP 3.5" disc drive service manual (disc commands) Message-ID: <m1U121T-000J4cC at p850ug1> Content-Type: text/plain I beleive it was specifically designed to be. It was intended that any systme that supported the 82901 could also use the 9121, no matter waht assumptions it made. In this repsect, the respose to the standard idenmtification coammends is the same, there is one extended command that returns a differnet value o nthe 2 drives so it is possible to tell them apart, but a ssytsem designed fo the 82901 wouldn't use that command. Also the total numebr of sectors per disk is the same -- IIRC the 82901 is double-sided 35 cylidner and the 9121 is single sided 70 cylinder. -tony