Free, Wired, Active and Inactive - a guide to your RAM
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From: Richard Tobin on 5 Jun 2010 10:00 In article <1jjmzwq.1qgsa5d12wwiatN%dempson(a)actrix.gen.nz>, David Empson <dempson(a)actrix.gen.nz> wrote: >It is "wired down" in that the system can't reallocate that memory for >another purpose. [...] >I haven't found anything which clearly explains where the Mac OS X usage >of the term originates. It was used in BSD before MacOS X came along, so they probably got it from there. >The term does seem a little odd, because "wired memory" was a term used >to describe read-only memory back in the early days where it really was >made up of wires. I'm sure the term "wired down" has been used for memory that's used by the kernel or a device and therefore isn't available for normal allocation for a long time. It's abbreviation to "wired" probably reflects its use in variable names and the like; for example in this comment from the FreeBSD source: /* * vm_fault_wire: * * Wire down a range of virtual addresses in a map. */ -- Richard
From: Rowland McDonnell on 5 Jun 2010 10:21 Richard Tobin <richard(a)cogsci.ed.ac.uk> wrote: > David Empson <dempson(a)actrix.gen.nz> wrote: > > >It is "wired down" in that the system can't reallocate that memory for > >another purpose. > > [...] > > >I haven't found anything which clearly explains where the Mac OS X usage > >of the term originates. > > It was used in BSD before MacOS X came along, so they probably got > it from there. Definitely, I'd say. Wired memory was not a concept in pre MacOS X Mac-land. Wired memory is a term used in Unix generally AFAIK - I've seen it in System V, HPUX, and even the Apollo Domain OS which is merely Unix-alike. IIRC, that is. > >The term does seem a little odd, because "wired memory" was a term used > >to describe read-only memory back in the early days where it really was > >made up of wires. > > I'm sure the term "wired down" has been used for memory that's used by > the kernel or a device and therefore isn't available for normal > allocation for a long time. It's abbreviation to "wired" probably > reflects its use in variable names and the like; for example in this > comment from the FreeBSD source: > > /* > * vm_fault_wire: > * > * Wire down a range of virtual addresses in a map. > */ I suspect that the concept of wired memory is the reason for the above use of terminology - that is, `wired memory' as an idea came first, then they used the phrasing for Unix even though it was no longer strictly applicable, beause it nevertheless got the right idea across well enough. Rowland. -- Remove the animal for email address: rowland.mcdonnell(a)dog.physics.org Sorry - the spam got to me http://www.mag-uk.org http://www.bmf.co.uk UK biker? Join MAG and the BMF and stop the Eurocrats banning biking
From: Simon Dobbs on 6 Jun 2010 07:17
On Thu, 3 Jun 2010 17:17:14 +0100, Jim wrote (in article <slrni0flca.1d05.jim(a)wotan.magrathea.local>): > <http://reviews.cnet.com/8301-13727_7-20006694-263.html> > > Short article but explains it rather neatly. > > Jim > yes- it was highlighted on June 3rd in Macfixit |