Saturday 3 October 2015

CPU Buyers Guide

CPU Buyers Guide

If you’re in the market for a new processor, this guide is for you…

Buying a processor can be a difficult task. A fast-changing market coupled with a constant flow of new innovations and technologies (some real, some just for marketing purposes) can leave you struggling to even understand the options available to you.


The first question that needs to be answered is why you should spend money on a processor at all, when you could spend your money on any upgrade. More RAM, a solid-state drive, a better graphics card – they all have the potential to improve your computing experience and squeeze more power out of your machine. Why spend the cash on a processor?

Well, plugging a new processor in your computer is the easiest way to revitalise an ailing machine. You don’t have to spend hours cleaning out old software and defragmenting hard drives. You don’t have to tweak registry settings or install helper applications. From the moment you switch your computer back on, it’ll be immediately faster and more capable.

There are downsides, of course. Processors can only be upgraded so far before you need to buy a new motherboard that contains the latest CPU socket and platform designs, and the installation of a new motherboard can have knock-on effects tantamount to buying a new computer entirely (which is why vendors often sell motherboards, processors and RAM as a bundle). So how do you determine which processors you should buy and how far they can be stretched before you have to spend even more money on an upgrade?

Between Carizzo’s recent delay and Intel’s latest Skylake release, the CPU market has once again changed, and that means it’s time to re-evaluate what you’re looking for in a processor and whether it makes sense to upgrade your platform, your chip or wait and see what’s coming next.

CPU Architecture


Processor architecture is a tough area to understand, with a lot of different technologies and capabilities competing to appear the most crucial. Is a 2GHz dualcore faster than a 1.8GHz quad-core? Which is the best socket and why? It’s not always easy to know. So what are you actually looking for when you buy a CPU?

Although it may be interesting to some users on a technical level, the fact is that you can’t really divine performance from the number of cores or the clock speed alone. AMD chips have more cores than Intel chips, but they’re built differently, so a quad-core AMD chip isn’t the same as a quad-core Intel chip. Likewise, a 3GHz AMD chip isn’t necessarily better than a 2GHz Intel chip.

The main thing to remember is that for modern CPUs, the number of cores and clock speed is now only of any significant importance when comparing two processors from the same line. If you’re looking at two Intel chips, then more cores and a faster clock speed probably means it performs better.

Perhaps the most interesting thing to look at is the chip’s ‘process’. This value will be referred to in nanometres, and refers to the size of features created during the fabrication process. For complicated physics reasons, the smaller the fabrication process, the more energyefficient a CPU is, meaning it’s usually faster and cooler than an otherwise identical chip with a larger process. All things being equal, the smaller fabrication is more desirable than the larger one.

Regardless of the amount of cores, clock speed or fabrication process, the ability to overclock a chip may also sway you. Any CPU with a ‘K’ suffix can be overclocked from its factory speed (provided the motherboard supports overclocking), so you can garner additional speed by looking for that feature.

Finally, CPU socket types are sometimes worth paying attention to, but not always. Although CPU sockets are designed to allow you to reuse them and upgrade your chip, it’s not unusual to find the socket deprecated by the time you come to upgrade. For this reason, people who upgrade infrequently need give little thought to the socket type when buying a processor (save for making sure it fits in the motherboard you buy).

Users at either extreme of the usage spectrum, however, may want to get the most current socket to allow for easy upgrades. Low-end users may find that spending a few extra pounds buying the latest socket will allow them to improve their computer’s speed in the future without the need to buy a new motherboard as well, while high-end users will want to buy the latest chips as soon as they’re available. In any case, socket type is mostly a compatibility issue, and unrelated to performance in any major way.

Intel Vs AMD


The big decision most buyers face is whether they should shell out for an Intel chip or go for an AMD equivalent. In recent years AMD has struggled to match Intel’s pace, but that doesn’t mean there isn’t a place for it in the market.

Whichever one you choose, it’ll dictate a number of other choices about your system – its features, its motherboard and RAM type, maybe even the type of graphics card you buy. And while they do the same thing, both processors take very different approaches to the task, which means they suit different types of users. So how do you choose?

Price is the place where most people start thinking about building their PC. AMD processors are uniformly cheaper than their Intel equivalents, although this doesn’t necessarily equate to them being better value in performance terms. When you compare raw CPU power, Intel’s chips outclass any AMD chips at the same price range by a significant amount. So if low price is more important than good value, AMD is a good choice, but only at the low end where Intel chips are significantly stripped back.

The decision becomes more complicated when you start to consider on-board graphics. The majority of Intel chips (but especially those at the low end of the market, which either have no on-board GPU or a very weak one) have worse GPUs than their AMD equivalents. Even when it comes to mid-range chips such as the Core i5 and the AMD A10, the latter’s graphics performance is better.

What this means is that if you’re building a gaming system, a mid-range Intel chip and a graphics card will perform about as well as a high-end AMD chip on its own, and the latter will be cheaper than buying the former two. This means that for budget gaming, AMD chips can’t be beaten. But if you have a graphics card of moderate capability already, an Intel chip will be a better investment – unless your graphics card is a Radeon and can be run in CrossFire mode with the GPU on an AMD chip.

Confused? We hope not, but you may want to re-read that paragraph to make sure.

Even Intel’s latest graphics technology, the Iris Pro (which appears in Skylake chips) isn’t quite a match for AMD’s on-board GPUs. But if you’re buying a Skylake chip, then it’s likely that price isn’t your primary concern, and high-end chips need high-end graphics cards to get the best performance out of them anyway.

It’s also worth noting that if you’re not building a gaming PC, then Intel’s on-board graphics are probably sufficient to run your system on. Non-gaming applications tend to benefit more from Intel’s fast CPU speed than AMD’s extra GPU capacity, so if you’re just putting together a general use desktop machine, we’d go for Intel in virtually every case.

If you’re building a system for other specialist use, then you may want to take into account a few other factors. System temperature is important in HTPCs and other compact systems, so chips with a low TDP are more desirable. AMD chips have a higher TDP than Intel chips, partly because its chips are less efficient. If keeping temperature low matters to you, Intel’s hardware will give you better results on that front. It’s hard to say which chip is ‘best’, but easier to say which is best for you.

Current Models


If it’s been a while since you bought a CPU, you might be wondering what the CPU landscape currently looks like. Here, we’ll explain the sort of terms you’ll encounter and which of them are worth looking out for.

• Intel: Ivy Bridge
Released in 2011, Ivy Bridge is Intel’s first line of 22nm processors, which used Socket 1155 interfaces. You can tell an Ivy Bridge chip by its model number which, in standard consumer chips, usually begins with a 3 (e.g. Intel Core i7 3770K). The last Ivy Bridge chips were released in September 2013, and at this point we wouldn’t recommend upgrading to one even if you can find them on sale!

• Intel: Haswell
The follow-up platform to Ivy Bridge was released in 2013 and still uses a 22nm process, but contained other improvements which made it around 10% faster. They use Socket 1150 interfaces and can be denoted by their 4-series model numbers (e.g. Core i5 4690K). Unlike most recent chip releases, Haswell’s successor (Broadwell) did not have a full desktop release, making the platform unusually prominent over the last two years. A refresh in 2014 introduced the ‘Devil’s Canyon’ variants, which had improved thermal performance and required Intel 9-series motherboards. If you’re looking at older Intel chips, a Devil’s Canyon Haswell would be the oldest we’d recommend.

• Intel: Skylake
Since most of Intel’s first 14nm chips from 2014, code-named Broadwell, were only available in mobile devices, the successor to Haswell is 2015’s Skylake. These are also 14nm chips, and they use Socket 1151 on Intel 100-series motherboards. At present there are only a few Skylake CPUs on the market, but this will increase dramatically over the next year. They can be recognised by the 6000-series model numbers, such as the Core i5 6600K.

Intel has just delayed its Cannonlake 10nm CPU line, so if you’re buying a new chip for the long haul and can afford the latest hardware, we strongly recommend buying a Skylake CPU. Beware, however, that it’s still new enough that there’s a slight premium, and that performance isn’t significantly better than Haswell chips unless you’re also using the integrated graphics (which have been substantially improved). You will, however, get support for DDR4 RAM, which makes Skylake a smart investment in the future of desktop computing.

• Intel Chip Lines
Within each of the Intel platforms, you’ll find a variety of lines for each chip. Pentium and Celerons are low-end budget chips designed for very light use and lowbudget systems. They’re aimed more at things like simple office PCs and point-of-sale hardware than home multimedia systems. For light home use, we’d encourage you to buy a Core i3 at the very least. If you’re building a gaming system, the Core i5 should suffice. Core i7 chips are mainly aimed at extreme computing enthusiasts, and cost a significant premium over the alternatives, especially at the high end. Only buy a Core i7 if you’re sure you know why you want one!

• AMD: Kaveri
AMD has effectively ceased production of its stand-alone FX chips for the time being, leaving its combination CPU and GPU platform – the APU – as the only real option for CPU-buyers. Kaveri APUs were released in 2014 and use 28nm Steamroller architecture. They’ve just started to be replaced by their successor, Carizzo, on mobile platforms, but are still popular on the desktop. Indeed, the latest chip refresh (code-named Godavari) came out in Q2 and Q3 2015, so they’re still well up to date. They use FM2+ motherboards and can be recognised by their 7000-series model numbers (e.g. A8-7650K).

Due to the delays and uncertainty around Carizzo, we recommend anyone wedded to the idea of buying AMD chips sticks with Kaveri for the time being. They’re cheap and competitive on price and power for any system that doesn’t have a stand-alone GPU as well, and that makes them worth considering.

• AMD: Carizzo
The Carrizo line of chips includes Excavator cores (succeeding Steamroller) and a new generation of GPUs. They will also be the first to support DDR4 memory, making them good for transitioning to a new platform. At present, the desktop variety is not expected until some time in 2016 and will be code-named Bristol Ridge.

Carizzo chips have a 28nm process, meaning AMD won’t be shifting to 20nm CPUs for another generation. Carizzo chips are expected to have 8000-series model numbers and use FM2+ sockets.

However, if you’re running an AMD system and want to upgrade to another one, then Carizzo is probably not going to be much use to you in the short term. Whatever comes next – code-named AMD Zen – is going to be so different from Carrizo that there’s little chance of salvaging the core components, and if you don’t upgrade now, it’s going to mean a long and pointless wait for your next AMD system.

The good news is that it’ll be a while now until any new chips are on the market, and that makes it a good time to buy your upgrades. Whether you buy Intel or AMD chips, you should easily get four to six months of them being the best you can get, if not longer. And when it comes to something as expensive as CPUs, hardware that holds its value is a rarity worth chasing.