Real and availible RAM

Eric Anderson anderson at
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
real memory  = 234815488 (223 MB)
avail memory = 221167616 (210 MB)


Eric Anderson	   Systems Administrator      Centaur Technology
Attitudes are contagious, is yours worth catching?

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