At 2008-07-05T13:04:19+02:00, Robert Heron wrote: > FreeBSD 7.0-R on i386 server with motherboard S5000VSA and 6GB RAM > onboard. BIOS version - 88 (the latest) > > Kernel includes: options MAXMEM=(6*1024*1024) > > And FreeBSD reports only: > > real memory = 2680160256 (2556 MB) > avail memory = 2617892864 (2496 MB) > > Why? What is wrong that FreeBSD sees only about 2.5GB instead of > 6GB?
(I ran into this question recently when buying a computer, and did some homework on it, however my understanding may be off the mark.) As mentioned in earlier replies, the problem isn't caused by the OS, but is a limitation of the i386 architecture, in which each byte of memory is indexed by a 32-bit integer. This means that an i386 machine can use only 2^32 bytes, i.e., 4 GB, of memory --- unless one uses pae(4). Some of the 2^32 addresses are used by devices like the video card, and by the BIOS. For instance, if the machine has a video card with 512 MB of video RAM, this means that less than 3.5 GB of memory can be used. It seems a safe bet in such a case to install at most 3 GB of memory. There is more info at http://www.codinghorror.com/blog/archives/000811.html http://en.wikipedia.org/wiki/Memory_address Raghavendra. -- N. Raghavendra <[EMAIL PROTECTED]> | http://www.retrotexts.net/ Harish-Chandra Research Institute | http://www.mri.ernet.in/ See message headers for contact and OpenPGP information. _______________________________________________ email@example.com mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"