Date: Thu, 04 Apr 2002 18:03:41 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: mjacob@feral.com Cc: Andrew Gallatin <gallatin@cs.duke.edu>, freebsd-current@freebsd.org, gibbs@freebsd.org Subject: Re: BUS_SPACE_MAXSIZE & isp driver. Message-ID: <3CAD05FD.4FE5B863@mindspring.com> References: <Pine.BSF.4.21.0204041715070.78599-100000@beppo>
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Matthew Jacob wrote: > Neither is really applicable here. The actual limits for alpha depend on the > platforma and how you implement it. Typically, the bigger alphas have been > implemented with a 2GB direct mapped window, and then, if they have it, a S/G > map setup for the rest (if any) of memory, which also can include ISA mapping. Thanks for the clarification. I was confusing BUS_SPACE_MAXSIZE with BUS_SPACE_MAXSIZE_24BIT and BUS_SPACE_MAXSIZE_32BIT. It's probably too late to rename BUS_SPACE_MAXSIZE to something like BUS_SPACE_MAXXFER. 8-(. > The current Alpha 2.4.18 Linux implementation is quite happy to DMA to > 4GB > on quite a few alphas. Ah. Reference code. > BUS_SPACE_MAXSIZE seems to be related to the 'largest xfer you will be allowed > to do at one time'- which is wrong because MAXPHYS is larger. Yeah, I get that now. No need to beat me up, I can take care of it myself. 8-) 8-). -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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