Date: Wed, 11 Feb 1998 14:08:08 -0500 From: Brian McGovern <bmcgover@cisco.com> To: hackers@FreeBSD.ORG Subject: Mapping phyical memory in to the PCI address range... Message-ID: <199802111908.OAA02578@bmcgover-pc.cisco.com>
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This question may be somewhat ill formed. Hopefully, I'll make myself clear. I'm looking at taking the Cyclades driver, and moving the I/O buffers that are normally in the on-board RAM of the card, and possibly moving them to be within the physical RAM of the PC. Cyclades supports this to some levels (although they never tried it). Apparently, the big requirement is the ability to lock down the physical memory for the buffers, and then manipulate this memory in such a way as it can be seen by devices on the PCI bus, su that the card's processor can DMA to it. The questions I have are: 1 - Does FreeBSD support the ability to map system memory so its available to the PCI bus. Also, what is the proper procedure for determining the physical address of this memory, and locking it in such a way as to always be available to the card. 2 - Would it really be worthwhile pursuing this endeavor? After all, a 1-2% gain on moving a single character really isn't a big win. However 25+% very well might be. -Brian To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe hackers" in the body of the message
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