Date: Sun, 13 Oct 2002 11:54:57 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: "M. Warner Losh" <imp@bsdimp.com> Cc: ticso@cicely.de, hch@infradead.org, wes@softweyr.com, dillon@apollo.backplane.com, vova@sw.ru, nate@root.org, arch@FreeBSD.org Subject: Re: Database indexes and ram Message-ID: <3DA9C181.D36065CA@mindspring.com> References: <3DA954CF.98B0891A@mindspring.com> <20021013.060851.113437955.imp@bsdimp.com> <3DA9B4A8.194A02FC@mindspring.com> <20021013.120847.31902907.imp@bsdimp.com>
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"M. Warner Losh" wrote: > I think that's all irrelevant. Cards with 32bits can't go about 4GB. > It is a far more fundamental problem. Even 32bit cards in 64bit slots > can't do this. 64bit cards could DMA into anywhere in the first > 64bits of RAM, of course. I think we are in violent agreement. 8-). > I was confusing what you said with "The DMA is based on a virtual > address" which is not quite the same thing. Sorry if this was confusing; it was meant to reference the mappability of the physical memory, not that the DMA targetted anything but physical memory. You *could* "check DMAability" by having a target area at some address Q above 32 bits, and then checking to see if the data went there, or to the address Q & 0x00000000ffffffff instead. This would require you to pick your areas carefully. Ugly, ugly. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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