Date: Fri, 19 Aug 2005 22:17:06 +0000 From: "Mikhail P." <miha@ghuug.org> To: freebsd-amd64@freebsd.org Subject: Re: 4 GB RAM showing up as 3, BIOS memory hole and all that Message-ID: <200508192217.06403.miha@ghuug.org> In-Reply-To: <43020F08.6070108@samsco.org> References: <20050815125657.A92343@cons.org> <20050816111428.A24284@cons.org> <43020F08.6070108@samsco.org>
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On Tuesday 16 August 2005 16:06, Scott Long wrote: > Intel Xeon systems typically do the remapping trick, so when you boot > FreeBSD i386+PAE or amd64 on them, they might show 4.5GB of RAM when > there reall is only 4GB (this is a limitation of how we compute RAM and > is purely cosmetic, but should be fixed). Many AMD Opteron systems do > not do the remapping and result in you loosing effective RAM. The > difference between Intel and AMD is because AMD puts the memory > controller into the CPU instead of in the PCI host bridge, so it's much > harder to have the two work together to do the remapping. I believe > that there are some Opteron systems that can do this, though. > > A junior doc writer task would be for someone to collect all of the > email responses that I give on this topic (I seem to get at least one > query a month) and turn it into an FAQ for the FreeBSD doc set. > > Scott Here's a dual opteron system we've got recently. Currently it runs=20 =46reeBSD-4.11 GENERIC kernel (just fresh installed). It has 4GB of actual RAM, and OS sees it: CPU: AMD Opteron(tm) Processor 246 (1992.77-MHz 686-class CPU) =A0 Origin =3D "AuthenticAMD" =A0Id =3D 0xf5a =A0Stepping =3D 10 =A0=20 =46eatures=3D0x78bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE= ,MCA,CMO V,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2> =A0 AMD Features=3D0xe0500000<<b20>,AMIE,<b29>,DSP,3DNow!> real memory =A0=3D 4227792896 (4128704K bytes) avail memory =3D 4117520384 (4021016K bytes) I'm not sure what BIOS settings it uses (system is overseas), but it is bui= lt=20 on identical Celestia barebone: http://www.monarchcomputer.com/Merchant2/merchant.mv?Screen=3DPROD&Store_Co= de=3DM&Product_Code=3D100944&Category_Code=3D1U M.
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