Date: Wed, 20 Feb 2002 09:26:08 -0500 (EST) From: Andrew Gallatin <gallatin@cs.duke.edu> To: Terry Lambert <tlambert2@mindspring.com> Cc: freebsd-arch@FreeBSD.ORG Subject: Re: intrest in MIPS 10,000 CPU? support Message-ID: <15475.45568.4884.470350@grasshopper.cs.duke.edu> In-Reply-To: <3C736DAB.4B6B4CEA@mindspring.com> References: <OE19w8GIgovcke7m99L00005a3b@hotmail.com> <20020219175111.O48401@blossom.cjclark.org> <3C736DAB.4B6B4CEA@mindspring.com>
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Terry Lambert writes: > I can get an Alpha for pretty cheap, but I can only stick 2G > of RAM in it because of FreeBSD limitations that are Alpha > specific. <...> > The only reason I would go for MIPS or Itanium or other 64 > bit machine would be to break the 4G of physical RAM barrier. Alpha actually has a rather nice framework for doing scatter/gather mapping in the pci chipset for DMA for address limited devices. This is how ISA dma is done on all alpha platforms (except for UP1x00, which uses an AMD 751 pee-cee chipset which has no such support and does bounce buffering) The limitations are FreeBSD specific, not Alpha specific. The limitation is all the various & sundry drivers which do: dma_addr = vtophys(va); Rather than using busdma. I think Bill Paul posted a patch for establishing a busdma framework for network drivers last year. I wonder what happened to that..? Of course, to get 4GB or more in a box, you're talking some fairly serious hardware (rawhide or ds20/dp264 family). Drew To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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