FreeBSD adds x86 PAE to address more than 4GB

PAE HAS BECOME FAIR GAME for conversation recently as 32bit processors start to hit the limitations of 4GB of physical memory. Intel, being the smart firm that it is, planned for this as long ago as the Pentium Pro. Back then it introduced Physical Addressing Extensions (PAE) and FreeBSD has just signed up for it.

PAE is a way for 32bit processors to escape the 4GB memory limit. It pushes that limit out to 64GB by paging memory just like the old 8bit processors used to do. In other words, it's a kludge. It is, however, a kludge that is supported by Linux, NetWare and higher end versions of Windows. And now FreeBSD too.

The PAE implementation in FreeBSD reads a little raw still. It has only just been made current and there are quite a few caveats. You can find a fairly comprehensive explanation over at FreeBSD.org. µ