Real and availible RAM
Eric Anderson
anderson at centtech.com
Mon May 5 11:12:36 PDT 2003
Kyle Rollin wrote:
> On Mon, 5 May 2003 09:30:30 -0400 (EDT), agent dero wrote
>
>>I have been looking through the kernel boot messages in /var/log
>>while working on some custom kernel compile work, and I came across
>
> something
>
>>that I think is very interesting, but doesn't make sense.
>>real memory = 100663296 (98304K bytes)
>>avail memory = 94580736 (92364K bytes)
>>
>>This tells me that FreeBSD recognizes my 98MB of RAM, but it only
>>uses 92MB? Are the 6MB of RAM that are left getting shafted, and
>>just using power, but not being addressed by FreeBSD? Does this slow
>>down my machine at all, I mean, is there a percentage to this? Where
>>only x% of 100% RAM is availible or usable?
>>
>
>
> <snip>
>
> If you look at the way x86 architecture is designed (and somebody else can
> feel free to correct me if I'm wrong), but system memory is often used in
> the caching/shadowing of BIOS. This is where a lot of system memory often
> goes before the OS is loaded - also, as Rob said, the kernel itself will
> take up memory before the rest of the OS is booted.
I believe that the BIOS steals the ram prior to the OS booting, so that
the box does not show that as part of the total ram.. Like:
CPU: VIA/IDT Unknown (1066.16-MHz 686-class CPU)
Origin = "CentaurHauls" Id = 0x693 Stepping = 3
Features=0x380b13d<FPU,DE,PSE,TSC,MSR,CX8,MTRR,PGE,CMOV,MMX,FXSR,SSE>
real memory = 234815488 (223 MB)
avail memory = 221167616 (210 MB)
Eric
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Eric Anderson Systems Administrator Centaur Technology
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