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Slow iMac using all 12GB of RAM..


macrumors newbie
Original poster
Aug 15, 2012
Help.. Im having a lot of trouble with mi iMac running extremely slow from boot up with hardly any applications running. I have 12GB of RAM installed and would expect a bit more sped in performance. Activity monitor shows 9.5GB of wired RAM leaving little free and inactive RAM to use and I have absolutely no Idea what wired RAM is.

Anyone have any idea??

Thanks for any help..


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macrumors 6502
Feb 18, 2004
Wilmington, DE
A better explanation of wired memory (From the Developer Library):

Wired memory (also called resident memory) stores kernel code and data structures that must never be paged out to disk. Applications, frameworks, and other user-level software cannot allocate wired memory. However, they can affect how much wired memory exists at any time. For example, an application that creates threads and ports implicitly allocates wired memory for the required kernel resources that are associated with them.

Table 2 lists some of the wired-memory costs for application-generated entities.

Table 2:  Wired memory generated by user-level software

Resource                    Wired Memory Used by Kernel
--------                    ---------------------------
Process                      16 kilobytes
Thread                       blocked in a continuation—5 kilobytes; blocked—21 kilobytes
Mach port                    116 bytes
Mapping                      32 bytes
Library                      2 kilobytes plus 200 bytes for each task that uses it
Memory region                160 bytes
Note: These measurements may change with each new release of the operating system. They are provided here to give you a rough estimate of the relative cost of system resource usage.
As you can see, every thread, process, and library contributes to the resident footprint of the system. In addition to your application using wired memory, however, the kernel itself requires wired memory for the following entities:

- VM objects
- the virtual memory buffer cache
- I/O buffer caches
- drivers

Wired data structures are also associated with the physical page and map tables used to store virtual-memory mapping information, Both of these entities scale with the amount of available physical memory. Consequently, when you add memory to a system, the amount of wired memory increases even if nothing else changes. When a computer is first booted into the Finder, with no other applications running, wired memory can consume approximately 14 megabytes of a 64 megabyte system and 17 megabytes of a 128 megabyte system.

Wired memory pages are not immediately moved back to the free list when they become invalid. Instead they are “garbage collected” when the free-page count falls below the threshold that triggers page out events.

All that being said, the amount of wired memory that you are seeing is not normal. I would recommend booting in safe-mode (hold shift during startup), disable Time Machine completely, and disable local backups with the command
sudo tmutil disablelocal
in a terminal window.


macrumors 6502a
Mar 11, 2012
Near Toronto
Just a quick question about installing memory - I have 2 2G and 2 4GB... they are showing up opposite diagonally in the About This Mac Memory. Is that OK? It says all memory slots are currently in use.


macrumors 6502a
Jul 7, 2012
You should have an application running with a memory leak. Activity Monitor will help you to find the one consuming that memory.
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