From owner-freebsd-current Wed Sep 1 16:40:58 1999 Delivered-To: freebsd-current@freebsd.org Received: from dorifer.heim3.tu-clausthal.de (dorifer.heim3.tu-clausthal.de [139.174.243.252]) by hub.freebsd.org (Postfix) with ESMTP id 829D0155C1 for ; Wed, 1 Sep 1999 16:40:48 -0700 (PDT) (envelope-from olli@dorifer.heim3.tu-clausthal.de) Received: (from olli@localhost) by dorifer.heim3.tu-clausthal.de (8.8.8/8.8.8) id BAA03349 for freebsd-current@FreeBSD.ORG; Thu, 2 Sep 1999 01:40:38 +0200 (CEST) (envelope-from olli) Date: Thu, 2 Sep 1999 01:40:38 +0200 (CEST) From: Oliver Fromme Message-Id: <199909012340.BAA03349@dorifer.heim3.tu-clausthal.de> To: freebsd-current@FreeBSD.ORG Subject: Re: HEADS UP! ATA driver (atapi DMA).. Organization: Administration Heim 3 Reply-To: freebsd-current@FreeBSD.ORG MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: TIN [version 1.2 RZTUC(3) PL2] Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Daniel O'Connor wrote in list.freebsd-current: > On 31-Aug-99 Kevin Street wrote: > > > Well 2MB/sec == 14x CDRom drive. Is it a 14x CDRom drive? CDRom > > > drives are typically limited to how quickly they can get data off > > > the platter. A faster bus transfer will not improve that. > > I should have mentioned that ... it's a 32x cdrom. dmesg says it > > claims to be able to do 5515 KB/sec. > > Which is slightly more correct.. > 32x = 32 * 150 = 4800 kb/s > > 1 spin = 150kb/sec The raw mode2 data rate is 176400 bytes/sec (not counting subchannel information, which is normally not transferred along with the raw data anyway): 176400 * 32 / 1024 = 5512.5 Kbyte/sec. That number is derived from the throughput of CD audio data: 176400 bytes/sec = 44.1 kHz * 2 channels * 2 bytes/sample. (There are 75 sectors per second with 2352 bytes each.) Don't know where those 5515 come from... Maybe they rounded generously... ;-) Regards Oliver -- Oliver Fromme, Leibnizstr. 18/61, 38678 Clausthal, Germany (Info: finger userinfo:olli@dorifer.heim3.tu-clausthal.de) "In jedem Stück Kohle wartet ein Diamant auf seine Geburt" (Terry Pratchett) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message