From owner-freebsd-hackers Fri Apr 14 19:46:33 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id TAA23393 for hackers-outgoing; Fri, 14 Apr 1995 19:46:33 -0700 Received: from gndrsh.aac.dev.com (gndrsh.aac.dev.com [198.145.92.241]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id TAA23387 for ; Fri, 14 Apr 1995 19:46:19 -0700 Received: (from rgrimes@localhost) by gndrsh.aac.dev.com (8.6.11/8.6.9) id TAA02395; Fri, 14 Apr 1995 19:43:38 -0700 From: "Rodney W. Grimes" Message-Id: <199504150243.TAA02395@gndrsh.aac.dev.com> Subject: Just how fast can we go... (was: Re: SCSI target) To: julian@TFS.COM (Julian Elischer) Date: Fri, 14 Apr 1995 19:43:37 -0700 (PDT) Cc: freebsd-hackers@FreeBSD.org In-Reply-To: from "Julian Elischer" at Apr 14, 95 07:15:02 pm X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Length: 1277 Sender: hackers-owner@FreeBSD.org Precedence: bulk [cc: trimmed to hackers, seems the best place, since we are talking about both scsi and 100MB/sec ether :-)] > > > > > > > > Well, with 100MB/S ethernet support now being a reality TCP/IP over > > SCSI only has an advantage for *wide* scsi controllers. > weeeellll, no, there are advandages in being able to transfer > 128KB of scatter-gather data in one hit with NO > cpu intervention..... :) A few comments form the if_de.c driver: * The above used to be true (the stupid restriction is still true) * but we gone to directly DMA'ing into MBUFs because with 100Mb * cards the copying is just too much of a hit. #define TULIP_RXDESCS 16 #define TULIP_TXDESCS 128 /* * First find out how many and which different pages * the mbuf data occupies. Then check to see if we * have enough descriptor space in our transmit ring * to actually send it. */ segcnt = tulip_txsegment(sc, m, addrvec, min(ri->ri_max - 1, TULIP_MAX_TXSEG)); The 21040/21140 chips are bus master just like a scsi controller, and can infact do some very large scatter-gather's in there own right. -- Rod Grimes rgrimes@gndrsh.aac.dev.com Accurate Automation Company Custom computers for FreeBSD