RJ45 wrote: > THe system has exactly 4GB of memory but the memory is not complitely > seen by the system. > > At boot thime I Get this warning > > 524288Kb of memory above 4GB ignored
A normal 32bit OS can only address 4GB RAM -- but your system has various L2 and other caches built into the CPUs, etc., which count towards the total RAM count. So the excess is trimmed from the main memory. If you need to use more than 4GB RAM then either switch to a 64Bit OS, or investigate 'PAE'. You can run the 64bit version of FreeBSD on Intel Xeons (so long as they support EMT64) or the various AMD 64 bit processors. Xeons don't have as complete 64-bitness as Opterons so performance may not be as good as running 32bit. Mind you that sort of thing depends heavily on the particular workload and you should benchmark against your expected workloads. PAE 'Page Alternate Extensions' is frankly a bit of a haque to allow access to more than 4GB RAM by giving each process it's own separate 4GB address space, rather than sharing the space between all processes. Any one process cannot grow beyond 4GB, but the total over all processes can be more than 4GB. There is support in FreeBSD but with some severe limitations. Many drivers are not compatible with a PAE system. > and then if I check > > real memory = 3757965312 (3583 MB) > avail memory = 3678597120 (3508 MB) > > I do not know why this happens. That number is the amount of memory less what is wired down for the kernel. If you're on a 'big' system -- with lots of RAM -- then the kernel itself has to be larger because it needs to allocate memory to contain page mappings etc. etc. Approximately 500MB consumed by the kernel is not unreasonable for such a machine. Cheers, Matthew -- Dr Matthew J Seaman MA, D.Phil. Flat 3 7 Priory Courtyard PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW, UK
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