Date: Wed, 18 Jul 2001 18:52:06 +0200 From: Erik Trulsson <ertr1013@student.uu.se> To: freebsd-stable@FreeBSD.ORG Subject: Re: FreeBSD 4.3 and 6G RAM Message-ID: <20010718185206.A94946@student.uu.se> In-Reply-To: <Pine.BSF.4.10.10107180920100.4917-100000@athena.uniserve.ca> References: <NFBBIJCJGLAFOKNCJHKHIEIBCGAA.jon@witchspace.com> <Pine.BSF.4.10.10107180920100.4917-100000@athena.uniserve.ca>
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On Wed, Jul 18, 2001 at 09:23:18AM -0700, Tom wrote: > > On Wed, 18 Jul 2001, Jonathan Belson wrote: > > > > > i have an intel 4400 platform equipped with 4 xeon processors and 6G ram. > > > > the mainboard is based on the ServerWorks ServerSet II HE chipset (by > > > > intel), which supports up to 16G RAM (or 32G, i'm not sure at the moment). > > > > > > > > i have installed FreeBSD 4.3-STABLE. > > > > > > > > unfortunately, the system seems unable to work with this amount of ram. > > > > > > FreeBSD does not support more than 4G RAM (at least not on x86, I > > > don't know about Alpha). > > > My suggestion would be to remove the extra 2G RAM from the machine and > > > see if things work better then. (FreeBSD will not be able to use it > > > anyway so you don't lose anything by removing it.) > > > > Dumb question: by my calculations, a 32bit address register can only > > address 2**32 bytes of memory, ie. 4GB. Is it possible for your > > average P3/Athlon to addres more than this? Does it use banking/ > > MMU tricks? > > > > A Xeon processor can address more than 4GB. Considering it is an Intel > process, I imagine they use segment registers to do this. The original > 8088/8086 was a 16bit processor but had a 20bit address space. You used > segment registers to choose blocks of memory you could access. Something like that but a bit more involved and complicated, yes. > > I believe the Xeon is the only x86 processor that can address more than > 4GB. Nope. I just checked the online manuals at www.intel.com and all Intel's x86 CPUs since Pentium Pro can do this. (This includes Pentium Pro, Pentium II, Pentium III, Pentium 4 and the Xeon versions of them.) (No reason to speculate when it is so easy to check the facts in the manual.) The physical address bus for all of these is 36 bits which gives a maximum of 64GB of RAM. You also need support from the chipset and the OS to actually access the extra memory. -- <Insert your favourite quote here.> Erik Trulsson ertr1013@student.uu.se To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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