If you are choosing between two different types of Mac, or two generations of the same Mac, you may be wondering just how much of a difference the processors will make. In this article we will endeavour to clarify the differences between the generations of processors, what you can expect from an i3, i5, i7, i9 or a Xeon processor, why it matters how many cores you get, and what Turbo Boost really means.

There are so many different terms used to describe the processor in the current crop of Macs that trying to figure out which is best for you is enough to make your head spin. So which processor should you choose? And does it really matter?

MacBook Pro

What generation of processor is in my Mac?

The names Sandy Bridge, Ivy Bridge, Haswell, Broadwell, and Skylake are Intel code names for its processor architectures. Sandy Bridge is the oldest, dating back to 2011, and Ivy Bridge was an update to that in 2012. Haswell came in 2013 and was a major re-design of the Ivy Bridge architecture. And Broadwell in 2015 was a relatively minor update to Haswell. Skylake first appeared in late 2015 in the 27in iMacs, then in 2017 Kaby Lake processors started to appear.

Kaby Lake was followed by Coffee Lake. Coffee Lake brought some big changes, with 6-core options and more quad core options at the entry-level. The initial Coffee Lake release was the 8th generation of Intel processors. In autumn 2018 the 9th generation launched - known as the Coffee Lake refresh - which added 8-core i9 processor options.

At the time of writing we are still waiting for the next generation of Intel processors. The expected successor was Cannon Lake, but Intel has encountered a number of problems with Cannon Lake. Ice Lake will follow Cannon Lake (assuming Cannon Lake ever makes it out of the labs in significant numbers).

The majority of Macs (as of August 2019) feature 8th generation Coffee Lake processors, the exceptions being the 15in MacBook Pro and the top-of-the-range iMac, which offer 9th generation Coffee Lake processors, and the soon-to-launch 2019 Mac Pro which will offer 8- to 28-core Intel Xeon W processors.  

There is also a Xeon W processor inside the iMac Pro, although this is an older generation than the one that will feature in the 2019 Mac Pro. That processor ranges from 8- to 18-core.

Xeon workstation processors have different codenames to the processors listed above but are based on the same Intel architecture.

We almost forgot to mention the entry-level iMac with its 7th generation dual-core processor. That Mac hasn't been updated since 2017 and the least said the better...

MacBook

How to choose between processors

Modern micro-processors are incredibly complex beasts, housing more than a billion transistors, each about 0.02% of the thickness of a human hair. And they do far more than the CPUs of old; those took inputs, executed instructions on them, and passed the output to memory. Today's processors are mini-computers, incorporating multiple cores, or CPUs, on one chip, alongside short-term memory, or cache, and even graphics processors.

There are two ways in which one processor can be better than another: the number of instructions it can execute in a given time period, and the amount of power it consumes doing so.

While the former is crucial for some applications, like encoding 4K video, rendering complex 3D models and animation, and some mathematics and scientific applications, for most of us it's the latter which should be of most concern.

The power used by a processor affects the computer in two ways: battery life and heat. Quite simply, all other things being equal, the faster a processor runs, the more heat it will give off and the more energy it will suck from a laptop battery.

Reducing that power consumption and making processors more efficient is at the heart of most of the improvements processor designers such as Intel have made in recent years. As a result, the more recent the processor in a Mac, the more efficient it's likely to be. And that explains why a newer processor will likely be better than an older processor, even if the number of GHz is smaller.

We will look at a number of other differences between processors below, including GHz (the processor speed as advertised, and the speed that can be claimed if Turbo Boost is active).

We will also look at the different processor types in each generation. For example, you can choose from an i5 and an i7 chip.

The other big difference will be the number of cores available, with dual-core, quad-core, and even 8- 12- and 18-cores available. We’ll also examine this below.

For context, here's a list of the various processors you will find in the current line up of Macs (at least at the time of writing: August 2018). We have excluded the build-to-order and Xeon options.

MacBook Air or MacBook Pro

MacBook Air:

  • 8th-gen, 1.6GHz Dual-Core, i5, Turbo Boost: 3.6GHz

13in MacBook Pro:

  • 8th-gen, 1.4GHz Quad-Core, i5, Turbo Boost: 3.9GHz 
  • 8th-gen, 2.4GHz Quad-Core, i5, Turbo Boost: 3.9GHz 

15in MacBook Pro:

  • 9th-gen, 2.6GHz 6-Core, i7, Turbo Boost: 4.5GHz 
  • 9th-gen, 2.3GHz 8-Core, i9, Turbo Boost: 4.8GHz 

21.5in iMac:

  • 7th-gen, 2.3GHz Dual-Core, i5, Turbo Boost: 3.6GHz 
  • 8th-gen, 3.6GHz Quad-Core, i3, No Turbo Boost
  • 8th-gen, 3.0GHz 6-Core, i5, Turbo Boost: 4.1GHz 

27in iMac:

  • 8th-gen, 3.0GHz 6-Core, i5, Turbo Boost: 4.1GHz 
  • 8th-gen, 3.1GHz 6-Core, i5, Turbo Boost: 4.3GHz 
  • 9th-gen, 3.7GHz 6-Core, i5, Turbo Boost: 4.6GHz 

Mac mini:

  • 8th-gen, 3.6GHz Quad-Core, i3, No Turbo Boost
  • 8th-gen, 3.0GHz 6-Core, i5, Turbo Boost: 4.1GHz 

How many GHz

GHz reflects the number of clock cycles per second. So a 2.3GHz processor’s internal clock beats 2.3 billion times per second. Hence people referring to the number of GHz as the clock speed.

Each range of Macs usually has more than one option in terms of GHz (with the exception of the MacBook Air which is only available at 1.6GHz).

Sometimes it will look like a more powerful Mac has a slower clock speed. This is invariably due to the Mac in question having more cores available. For example, the 3.1GHz 6-Core iMac costs considerably more than the  3.6GHz Quad-Core model. At first glance that might look like a bad deal, but that’s six 3.1GHz cores, rather than four 3.6GHz cores. And the more cores the better, as we will explain below.

iMac or MacBook Pro

What is Turbo Boost

Another thing to note in terms of GHz is the Turbo Boost figure. The simplest way to think of Turbo Boost is as a way of safely over-clocking the cores on a processor. This figure can sometimes give a clue as to how one generation’s processor compares to the next.

The Turbo Boost controller samples the power consumption and temperature of the cores hundreds of times a second while monitoring the demands made of them by software. If any of the cores are being driven to their theoretical maximum, Turbo Boost can, if enough power is available and the temperature is at a safe level 'over-clock' the core and enable it to work faster.

So the eight cores in a MacBook Pro's 2.3GHz 8-Core i9 processor can, if needed, be pushed to 4.8GHz subject to power consumption and heat dissipation.

And a 1.6GHz MacBook Air dual core processor can be pushed to 3.6GHz, while the ageing entry-level iMac, with its 7th generation processor has a 2.3GHz dual core processor, but that can still only be pushed to 3.6GHz.

One thing to note, some processors won't be able to Turbo Boost. These i3 processors, found in the 3.6GHz Quad-Core iMac and the 3.6GHz Quad-Core Mac mini do not include Turbo Boost, so the 3.6GHz speed is never going to be over-clocked. However, that may not matter to you if you won't benefit from Turbo Boost.

Why would you need Turbo Boost? Turbo Boost kicks in when you aren't using all the cores, so the clock speed can be incresed on the cores that are in use. So, Turbo Boost is a feature that will benefit you most if you aren't using applications that use multiple cores.

Why you might not want Turbo Boost? When Turbo Boost is in use your computer will be using more power, so if you have a laptop it might not be in your interest to have Turbo Boost.

iMac 2019

Core M, i3,  i5, i7, or i9

Wondering how i5 is better than i7, or if i3 is going to be inadequate? We look through the different processors right up to i9.

Core M

Intel makes mobile versions of its chips. The M, which appeared in the first Retina MacBook when it launched in 2014, was the first Intel laptop chip that didn’t need a fan to cool it. Its power efficiency is what allowed Apple to build a notebook that was thin, weighed only 900g, and clocked up 9 hours of battery life while running at a reasonable speed.

There were three M processors with increasing performance: m3, m5 and m7. The M processors aren't currently being used by Apple.

Core i3

There are a couple of Macs that currently ship with i3 processors, which, as we said above, don't feature Turbo Boost.

Core i5

The majority of Macs use Intel's i5 processors. Right now the i5 tends to be quad-core or 6-core, but you'll notice that there is an old i5 processor in the entry-level iMac, with a dual-core (it's an older generation).

Core i7

i7 used to be the big differentiator, but there aren't currently any i7 processors in the Mac range. However, it's worth looking out for if you are thinking of purchasing an older Mac. This is because, in older generations of Macs, when it came to quad-core the i5 and i7 versions were not equal.

The Quad-Core i7, which was once used in the 15in MacBook Pro offered some features that the Quad-Core i5 didn't, one of which was Hyper threading, which we discuss below.

Another difference was the size of the cache, which we will also discuss later.

Thanks to these features, i7 processors were better for multitasking, multimedia, high-end gaming, and scientific work.

Core i9

Intel's i9 processors are the new kids on the block. They arrived with the 9th generation Coffee Lake refresh, and have up to 8-cores.

Core i9 is faster, but you don't necessarily need it and that extra power will mean a sacrifice when it comes to battery life.

Xeon

Xeon processors are workstation or server processors. Xeon processors support more memory than the i5/i7/i9 processors - the 2019 Mac Pro will offer up to 1.5TB RAM. You will also find more cores available on Xeon processors, up to 28-cores in the Mac Pro.

How many cores

Among the Macs on sale currently you will generally find dual-core, quad-core, 6-core, and 8-core options.

If you need more cores, the 2013 Mac Pro shipsed with a Xeon processor with a choice of 6-, 8-, and a 12-cores. The iMac Pro offers 8-, 10-, 14- and 18-cores. And the 2019 Mac Pro will offer 8-, 12-, 16, 24, or 28-cores. Read all about the new Mac Pro here: Mac Pro release date.

The more cores in your CPU the faster it will perform (and the more energy it will guzzle).

iMac cores

CPU Cache

The more processor cache you have the better. Cache is on-board memory and it helps the processor deal with repetitive tasks faster, because information can be held in the memory. Greater amounts of cache will also help with multitasking, because several tasks can be run simultaneously.

Hyper threading

Hyper threading allows the processor to handle twice as many 'streams' as it has cores, by fooling software into thinking it has twice as many cores. So a quad-core processor with hyper threading should be able to execute four times as many sets of instructions in a given time period as a dual-core processor with the same clock speed but without hyper threading.

This means that a quad-core i7, for example, can act like it has eight cores, but a quad-core i5 will only be able to use the four cores available to it.