From owner-freebsd-questions Thu Apr 25 14:39:27 1996 Return-Path: owner-questions Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id OAA12288 for questions-outgoing; Thu, 25 Apr 1996 14:39:27 -0700 (PDT) Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.211]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id OAA12279 for ; Thu, 25 Apr 1996 14:39:19 -0700 (PDT) Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id OAA25496; Thu, 25 Apr 1996 14:34:04 -0700 From: Terry Lambert Message-Id: <199604252134.OAA25496@phaeton.artisoft.com> Subject: Re: bounce buffers To: alk@Think.COM (Tony Kimball) Date: Thu, 25 Apr 1996 14:34:04 -0700 (MST) Cc: questions@FreeBSD.ORG In-Reply-To: <199604250653.BAA01917@compound.Think.COM> from "Tony Kimball" at Apr 25, 96 01:53:51 am X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-questions@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk > Under what circumstances are bounce buffers indicated? > Are they not indicated in all systems using >16MB DRAM? > My impression was that all such systems would require > bounce buffers in order to support DMA generally, while > no other systems would require bounce buffers. Bounce buffers are required for 24 bit (ISA) bus master DMA to addresses over 16M. If you are not using ISA cards, or an EISA system with a HiNT chipset, or a broken VLB card, you don't need bounce buffers. Normal EISA, normal VLB, and all PCI systems work without bounce buffers. Technically, if you had an Amiga, and FreeBSD was ported to it, or an Alpha with an EISA bus, and FreeBSD was ported to it, you'd need bounce buffers for the coprocessors that could only copy to/from "chip ram". Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.