Mac terminal number of cores

Whither Adobe Photoshop CS4, with its gross underutilization of even two cores for many tasks?

This will slowly change, as market pressures come to bear, but four cores is enough for most users, with six cores being plenty except for specialized tasks. In the example at right, the example Mac Pro Nehalem has two 2. All 16 virtual cores are fully utilized. At the opposite extreme, some programs are single-threaded; they make use of only a single core, no matter how many cores are available. Photoshop CS4 is single-threaded for opening and saving files More , a serious performance problem which has gone unaddressed for years.

Examples of CPU usage

Some applications have few or no CPU-intensive operations, but can benefit from threading —doing more than one task at once, such as copying files, emptying the trash and compressing a folder at the same time. The failure to use threading is often more of an issue than multi-core support because it prevents the user from doing useful work while the task runs.

An egregious example is Adobe Photoshop CS4, which prevents any other useful work while it opens or saves a single file, which can take several minutes for large files.

virtualization - Number of cpus and cores in macbook pro? - Ask Different

See How to speed up opening and saving files in Photoshop. By working in parallel, multiple CPU cores can greatly accelerate multiple tasks, or portions pieces of the same task. This is called task threading or simply threading or threaded execution. This means that an 8-core system can potentially run about 4 times faster than a dual-core system! Only one person can drive a car at a time! There are plenty of computing tasks that have such limitations; parallel execution threading has been the subject of computer science research for many decades.

Large numbers of CPU cores are the future, along with using cores from more than one machine. As of late , only the Mac Pro and XServe offer more than two cores.

Number of CPU cores on Linux and OS X

The other machines I term dead-end Macs , because improvements in application code still only have two cores to exploit, whereas Mac Pros with 4 or 8 cores have headroom for future improvement in applications, extending their service life. Think of a garden hose as compared with a fire hose—the fire hose allows a much greater volume of water to pass through it per unit time: All CPU cores must share access to the same physical memory and therefore have to take turns to read from or write it. Like the Ladies bathroom at a movie theatre, a long queue can form waiting for access—the cores actually become idle for much or even most of the time that they are allegedly computing; they are forced to wait most of the time for their memory access operations to complete.

This is why one can observe full CPU utilization on an 8-core system How , but see only only Scalability keeps improving with newer chips and faster memory however.

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With a well-engineered program, memory bandwidth is one key reason why an eight core machine might not run any faster than a quad-core machine, or might even run a little bit slower. However, programs that are primarily computation-intensive can show exactly double the performance with eight cores instead of four. Like memory bandwidth, disk speed or network speed can throttle performance. Any program capable of using all 8 cores might needs a lot of data think HD video.

sysctl -n hw.ncpu: OS X

Other programs are all about computation, and have no such dependency. A well-designed program will be able to process data while simultaneously reading from disk , leading to a situation in which the CPU speed has hardly any effect on execution time.

How to Modify an OS X install disc to work on other computers.

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