Date: Wed, 7 Feb 1996 22:14:14 +0100 From: se@zpr.uni-koeln.de (Stefan Esser) To: Peter Dufault <dufault@hda.hda.com> Cc: hasty@rah.star-gate.com, fwmiller@cs.umd.edu, hackers@freebsd.org Subject: Re: PCI programming Message-ID: <199602072114.AA22888@Sysiphos> In-Reply-To: Peter Dufault <dufault@hda.hda.com> "Re: PCI programming" (Feb 7, 9:00)
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On Feb 7, 9:00, Peter Dufault wrote: } Subject: Re: PCI programming } We forwarded this gentleman's private e-mail to the list. } In general we ought to avoid this, and invite the originator to } send to the list himself. } } > Both these devices are Bus Masters.. } > neither contains accessible ram. } > you can't really pass data directly from one master to another. } > } > you need a RAM scratch pad that both devices can access. } } A while back I set it up to DMA directly from a VME disk array } controller directly out a high speed multidrop card to an HDTV } frame buffer. The disk array controller was set up to generate } non-ascending addresses. } } I suspect the NCR PCI SCSI controller can do the same sort of thing } since the NCR 725 can be set up that way, and a network card with } a PCI visible FIFO could be the DMA target. The NCR 53c8xx can do SCSI bus to memory block moves. But it can't do DMA port writes to some Ethernet chip, since it actively generates only memory accesses (it can rrespond to memory mapped or port I/O accesses to its registers). But since bus-master PCI Ethernet chips have identical DMA capabilities, you'll be able to have the NCR fill a sector buffer in DRAM and the Ethernet chip send it as soon as it is complete. Neither chip has FIFOs that could hold a maximum size Ethernet packet, and the speeds aren't matched well enough to directly connect one chip's output with the other chip's input ... Regards, STefan -- Stefan Esser, Zentrum fuer Paralleles Rechnen Tel: +49 221 4706021 Universitaet zu Koeln, Weyertal 80, 50931 Koeln FAX: +49 221 4705160 ============================================================================== http://www.zpr.uni-koeln.de/~se <se@ZPR.Uni-Koeln.DE>
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