From owner-freebsd-hackers Tue Sep 12 20:03:59 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id UAA29893 for hackers-outgoing; Tue, 12 Sep 1995 20:03:59 -0700 Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.34]) by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id UAA29875 for ; Tue, 12 Sep 1995 20:03:46 -0700 Received: (from bde@localhost) by godzilla.zeta.org.au (8.6.9/8.6.9) id MAA19273 for hackers@FreeBSD.org; Wed, 13 Sep 1995 12:59:47 +1000 Date: Wed, 13 Sep 1995 12:59:47 +1000 From: Bruce Evans Message-Id: <199509130259.MAA19273@godzilla.zeta.org.au> To: hackers@FreeBSD.org Subject: Re: higher density diskettes Sender: hackers-owner@FreeBSD.org Precedence: bulk >> ... The FreeBSD driver uses a head >> settle delay of hz/16 ticks, i.e., between 50 and 60 ms. This is much >> longer than necessary. I think the spec is 15 msec. >The spec suffers from a lack of reality. We've once had hz/32, and >got (too) many problem reports. That's why the more conservative >value has been used. Perhaps the extra delay is compensating for a bug elsewhere. >I know that the existing driver is not at the end of optimization, but >i'm not sure whether a potential gain of 25 % or less in speed would >be worth the effort. People usually only recognize speed changes by a >factor of 2 or more. 25% was for the simple sequential case that the existing driver handles best. Bruce