Hard Choices: How To Choose The Right CPU

Apparently, some of you don't dedicate every waking hour to keeping up with PCI Express lane counts, silicon production nodes and CPU socket redundancy. I know, some people, eh? But with that in mind, plus the tendency for product-driven reportage to get a bit jargon heavy, not to mention some significant recent CPU-related developments from Intel of late, now feels like a good moment to stick a peg in the sand, pull all the current CPU options together, outline the key technologies and issues and then point you in the direct of a few best buys. It's time for another semi-newbie's guide to CPUs.

We've done this before, of course. But that was my very first post on RPS way back in January 2012. That's so long ago, I'm not entirely convinced mankind had grasped the concept of a circular device revolving on an axial bearing, much less used advanced lithography to create staggeringly dense integrated circuits with hundreds of millions, even billions of transistors. But apparently there were CPUs back then and I wrote a post to prove it. Whatever, the time is ripe to deliver an update. For those of you who simply want a TL;DR list of the best CPUs to buy, jump straight to the bottom.

CPU sockets and chipsets

We'll start with platforms and sockets. For Intel CPUs, that means the mainstream LGA1150 and the newly minted high-end LGA2011-v3. Well, I say mainstream of the LGA1150 socket. Until recently, I viewed it (and its LGA1155 progenitor) as really the only game in town given the punitive pricing of all things LGA2011. But with the new Haswell-E family of CPUs from Intel, LGA2011 in revised -v3 form has become relevant once more.

For clarity I'll insert a couple of points of housekeeping here. In this article LGA2011 and LGA2011-v3 are interchangeable unless I specify otherwise. I'm talking about the latest kit you can buy today and for some reason typing out the '-v3' every single time both does my head in and simply looks unsightly. Bloody Intel.

An LGA2011-v3 motherboard, yesterday

Similarly, regards Intel's mainstream tech, we're talking here about current kit which means LGA1150 CPUs for LGA1150 motherboards. If you're looking for a CPU upgrade for, say, an old LGA1156 motherboard, that's a different question and one we can address in the comments below.

Chipset-wise, I'll keep the advice simple for LGA1150 CPUs. Don't argue, just go with the Z97 chipset. For LGA2011-v3 chips, there is only one chipset, the X99, so that's a done deal.

DDR3 vs DDR4

So what are the differences between these two platforms? Four key things, really. Firstly, system memory or RAM. LGA1150 is a dual-channel DDR3 setup which means you only need two sticks of of bog standard DDR3 memory to get things working optimally. LGA2011-v3 is a quad-channel affair and thus you'll need four sticks for full memory bandwidth.

And not just four sticks of any old stuff, but four sticks of relatively exotic DDR4. The result is way more bandwidth, but also considerably more cost, a common theme for LGA2011, you might say.

Generally, DDR4 has plenty to offer. Higher speeds (in the long run, anyway). Lower power consumption. Greater data density. But, in truth, the last thing the quad-channel LGA2011 platform for desktop PCs needs is more CPU memory bandwidth. Especially, given LGA2011 chips don’t have integrated graphics competing with the CPU cores for bandwidth.

Instead, DDR4 is more of a benefit for multi-socket servers, which is really what LGA2011 platforms are about. That said, DDR4 will be a boon for mainstream CPUs with integrated graphics when it arrives with Skylake, probably at the end of next year. For now, it's just something you have to contend with if you go with LGA2011.

PCI Express

Next up is PCI Express connectivity. PCI Express is essentially a high bandwidth, multi-purpose interface for connecting things to your system, be that a graphics card or, increasingly in future, a hard drive. The key point you want to grasp here is that PCI Expree lanes situated on the CPU itself (otherwise know as 'on die') are far preferable to those on the chipset, since the latter share bandwidth with all manner of devices and peripherals.

Currently, the LGA1150 platform has 16 PCI Express lanes on-die. In theory, you want every one of those to feed just one graphics card. In practice, we're talking the latest 3.0 revision of PCI Express and thus eight lanes are plenty.

Forget integrated CPU graphics, you need a proper 3D card

Where things get complicated is when you want to run multiple graphics cards and then perhaps throw one of the latest PCI Express solid state drives into the the mix. Suddenly, you might want two graphics cards with eight lanes each and another four for that SSD. And LGA1150 doesn't deliver.

LGA2011, however, does. The latest revision offers at least 28 lanes, allowing for that theoretical dual-GPU-plus-SSD arrangement. It's also possible in future that single GPUs might begin to bump up against the constraints of an eight-lane PCI Express connection. If that happens, LGA1150 will be problematical for single-GPU systems with fast SSDs.

Integrated graphics

Next up, integrated graphics. Put simply, LGA1150 has it, LGA2011 doesn't. Broadly speaking, re desktop rigs for gamers, having the integrated graphics isn't much of an advantage. At best it's a handy fall back if you have a problem with your PC and you want to rule out a faulty graphics card.

The point is that if you like games, you definitely want a proper graphics card. So while I don't actually view the presence of integrated graphics in LGA1150 systems as a negative, nor do I bestow much by way of bonus points.

The CPUs themselves

The final differentiator between LGA1150 and LGA2011 is what we're really here for, the CPUs themselves. LGA1150 offers a huge spectrum of chip choices, from bargain basement dual-core chips to pretty pricey quad-core affairs with multi-threading support and unlocked multipliers for easy overclocking.

Consequently, the branding gets pretty complicated with Pentiums, Core i3s, i5s and i7s in the mix. For the most part, my recommendation is for quad-core as a minimum, so that means some kind of Core i5 processor. I'll come to the specifics in a moment.

LGA2011 currently only offers a trio of high end CPUs, with six and eight-core models on offer. Again, I'll come to the specifics in a moment, but LGA2011 chips are much easier to choose from

That overclocking thing

This is something I covered in a previous Hard Choices post. Have a scan through that for the basics on what to do, which kinds of chips can be overclocked and what you'll need to do it.

Something like Corsair's H60 water cooler is a good long-term investment

However, what I do want to emphasise here is that moderate overclocking of 'unlocked' CPUs is very easy, very safe and very effective. I'd also like to slightly revise my rather dismissive attitude to water cooling in that piece. I'm now more of the view that a water cooler is a worthwhile long term investment and needn't be expensive – basic but effective prebuilt water coolers for CPUs kick off around £50 or $65.

You can usually hang on to your water cooler over multiple platform and CPU upgrades and it makes for a quieter, cooler more reliable PC, I reckon.

Which chips should you actually buy?

Until recently, it was all about how much you wanted to spend on an LGA1150 rig. And for a lot of people, that's still the case. If you're absolutely poverty stricken, the new Pentium Anniversary G3258 (sometimes known as the 'Pentium K') is a good shout at about £50 or $70, but only if you are willing to overclock.

It's dual-core and lacks Intel's HyperThreading technology, but it will do over 4GHz with ease and that gives you excellent performance in a couple of software threads, which is good enough for most games.

That said, I'd still prefer four cores for those handful of games that do scale nicely across multiple cores and for a modicum of future proofing. In that context, I reckon you have two choices. Either get the cheapest quad you can find for the LGA1150 socket – so probably the £130 / $190 Intel Core i5-4430 - or step up to the unlocked Core i5-4690K for £170 / $239 (the lower-clocked 4670K doesn't seem to be much cheaper).

And that's where I'd now draw the line on LGA1150. In the past, chips for the old LGA2011 platform were so expensive, it made sense to consider HyperThreaded Core i7 chips for the mainstream platform. But now you can get the six-core Core i7-5820K for under £300 ($400) I really think if you're going to step beyond a quad-core, quad-thread Core i5, it's worth making the full leap to six cores and 12 threads on LGA2011.

Yes, there are additional costs with LGA2011. The motherboards are more expensive, so too the RAM. But there are real benefits and the price jump isn't nearly as bad as before.

Hang on, what about AMD?

I've been a bit naughty and not mentioned AMD at all so far. I have two problems with AMD right now. One is weak single-threaded performance, and that's a killer in games. The other is the speed with which AMD platforms and chipsets are being left behind.

Platforms for AMD's FX chips look horribly off the pace, these days. I tend to lament the rate at which Intel integrates features like USB 3.0 or PCI Express storage. But AMD really has left its FX platform to rot. Admittedly, platforms for AMD's APUs have had more love. But then I'm back to that weak single-thread problem.

Even the latest AMD FX chips aren't great gaming CPUs

There are specific situations and price points where AMD CPUs still make sense. A very cheap AMD Kaveri rig as a media PC with light gaming capabilities? Maybe. But if you want generic / no brainer advice for building a proper gaming PC, apologies to AMD but mine is to stick to something close to the Intel CPUs I've mentioned above.

Should you wait for Broadwell or even Skylake?

We've touched on Intel's upcoming Broadwell CPUs, due early next year, before https://www.rockpapershotgun.com/2014/08/14/14nm-cpus/. Personally, I very much doubt Broadwell will do anything dramatic on Intel's mainstream platform. It'll be the same old incremental quad-core affair that we've become used to. Factor in the recent overhaul of LGA2011 and I'd say right now is therefore a great time to buy.

As for Skylake, Intel's CPU family that follows Broadwell, it's likely at least a year away. Yes, it will improve the PCI Express lane limitations of Intel's existing mainstream platforms I mentioned earlier. But I don't think that's worth a year's wait.

TL;DR

Intel
LGA1150
- Pentium Anniversary G3258 £50 / $70
- Core i5-4430 £130 / $190
- Core i5-4690K £170 / $239

LGA2011-v3
- Core i7-5820K £290 / $380

AMD
- Don't bother for now

Good luck and science speed!