The right processor


First a rare 10-minute video from AMD


 Amazing that we can buy such technology for less than Rs 5000. No?

Processor — or CPU — is the heart of a computer. Ideally, it ought to be the first component you finalize if you are building a new computer. The reason, apart from the fact that CPU is very important, is that the choice here decides what other components will go in the computer. Deciding the CPU is akin to laying the foundation on which rest of the system can be build

Before I talk about the CPU I have selected for my build, here are a few points that I am sure will help anyone understand CPUs better. This will help you when you are buying a new computer 

1-    Only two companies make CPUs for personal computers for mass market. These are AMD and Intel.

2-    Currently, Intel distinguishes its CPUs in the following manner:

a)    Xtreme processor:  This is the top of the line processor and the model number has X in it. It’s very expensive and suitable only if you are a video editor or animator in world-class movie studio. Nowadays, Xtreme processors have 6 cores with hyper threading (HT), giving them ability to process 12 threads at the same time.

b)    Core i7: High-end processors supposed to go into gaming and high-performance machines. Every Core i7 processor has at least 4 cores with HT.

c)    Core i5: Has 4 cores but no HT (not applicable to mobile processor). Have somewhat less cache compared to Core i7.

d)    Core i3: Has 2 cores but with HT. So they can process four threads at the same time. Less cache compared to Core i5.

e)    Pentium: Yes, the name still survives. Though Pentiums nowadays are budget CPUs. They have 2 cores and no HT.

f)    At the same time, there are a few suffixes. X is for Xtreme. K is for processor that are unlocked and can be overclocked (will talk about it later), T is for power efficient processor, processor with S have smaller footprint, those with M in the name are mobile versions for laptops, and CPUs with U go into ultrabooks.

g)    Since 2006, Intel follows Tick Tock model. This means it brings out a new family of processors every year. Tick, like Sandy Bridge, is a new architecture. Tock, like Ivy Bridge, is moving old architecture to a new manufacturing process. Core i remains the same but model numbers change. So, be careful while getting one. You should always buy the latest CPUs. For example currently, you will find both Core i5 2500 and Core i5 3550. The difference is more than just the number. The former belongs to Sandy range and is no longer a recommended buy.  

3-    As far as AMD is concerned, here is how it handles naming of its CPUs

a)    FX series is the top-end. Processors have 4 to 8 cores.

b)    Phenom II sit below FX series. There are different categories in Phenom II family. In fact, there are too many models to talk about but generally in the market (Flipkart is an example) you are likely to find Thuban (X6 with six cores), Deneb (X4 with four cores) and Callisto (X2 with 2 cores).

c)    Currently A Series chips are the most exciting CPUs from AMD. The company calls them Fusion processors because they have a graphics chip inside CPU. Intel’s CPUs too have the same feature but graphics chip in AMD CPU is slightly better than the one in Intel CPUs. If you don’t plan to do 3D gaming, the 4-core A series CPUs are good option for a desktop.

d)    AMD sells Black Edition processor for overclockers.

Just a few more points 

1-    Cache is important but not much. Clock speed is more important.

2-     Model number is good way to indicate the relative standing of a CPU in the line-up

3-    Both AMD and Intel offer something like burst mode where, depending on the work load, CPU ramps up the speed. The lighter the work load, higher the CPU will go. Higher is better.

Edit: On Twitter Vikas Kumar Das said that the line "the lighter the work load..." should read as "the higher the work load...". 

Well, in a way he is right. When the CPU is not doing anything it idles at very low speed to save power. For example the lowest c-state for Intel CPUs is 1.6Ghz. So when the load on the CPU goes up, its speed ramps up. 


But that is not really how the Turbo feature works. The amount of turbo doesn't depend on the work load. It depends on the state of TDP. Take the example of Core i5 2500 that runs at 3.3Ghz. It has a TDP of 95W. Even when it is under load, the TDP in reality might be just 75W. This means it has 20W headroom. CPU uses this headroom to apply turbo and increases the speed of the CPU beyond its specified limit. But why the line "the lighter the work load..."? It works like this: when the load is lighter, means only one core is engaged, the speed will ramp up to 3.7Ghz. If two cores are involved (heavier work load) it may ramp up to just 3.6Ghz. When three cores are involved (even heavier workload), the turbo is likely to reach only 3.5Ghz. When all cores are engaged (heaviest work load) the turbo won't scale higher than 3.4Ghz.      

4-    For most people, getting a CPU with more than four cores is unnecessary at the moment. In fact, for mainstream use, 2 Intel cores with HT or AMD’s 4 cores are more than enough. But there are special cases where more cores are better. For example, if you are a multimedia pro or a developer, go for more cores. But if you are a pro, you already know that. Right?

5-    AMD’s cores ≠ Intel’s cores. Intel has a better performance per instruction (or clock). At the same time, Intel processors are also more expensive.

6-    TDP means the amount of heat a CPU is going to produce. This is closely tied to power use. It’s basic physics. More TDP also means higher power use. If you want to assemble a power-efficient PC, go with a CPU that has lower TDP.

7-    Easy solution: Select an Intel Core i3 or AMD A series processor for general purpose computer (web browsing, watching films, office work etc). Get a Core i5 if you are going to play heavy 3D games on the computer or will be keeping the same computer for at least 4 years. Get Core i7 if you are a power user doing lots of multimedia work or plan to keep computer for over 5 years. Get K version of Intel CPUs (there are generally two — one each for i5 and i7 series) if you plan to overclock.

The CPU that I have selected


My choice is Core i5 3570K. And if you have read 700 odd words that I have written so far, I am sure you know why.











But to wrap it up…

1-    Core i5 3570K is an Ivy Bridge CPU and is currently among fastest computer processors a consumer can buy. This fits well in my plan to build a fast general-purpose computer. On the average, the fastest is Core i7 3960X which costs above Rs 60,000. But it is based on an older architecture (Sandy Bridge). For all practical purposes, Core i7 3770K (Ivy Bridge) ties up with the Xtreme processor despite having a price of around Rs 20,000. For my workload, Core i5 3570K is going to be less than 10% slower than Core i7 3770 (20 seconds vs 22 seconds) as HT doesn’t make much difference for mainstream users once they have already have 4 threads/cores because most of the programs and games have poor scaling with the number of cores. But in terms of price, there is a difference of nearly Rs 6000. This makes Core i5 3570K better value for money for me.

A note about AMD. While A series CPUs are nice, for enthusiasts they are just not enough. The problem is that performance gap between AMD’s top CPUs and Intel’s top CPUs is huge. For example, the average difference between Core i5 3570K and FX-8170 is likely to be over 30 to 40%. And the Intel CPU also uses less power! 

2-    I can save around Rs 1500 by going with a non-K version. But I don’t like anything locked, whether it’s a smartphone or a processor. K version means I will be able to run it faster than what Intel officially mandates. For example 4.2 GHz vs the default speed of 3.5Ghz.

3-    Ivy Bridge supports PCIe 3. This is not relevant at the moment because no graphics card requires this much bandwidth but may help in future.

4-    Ivy Bridge also supports some crazy RAM speeds compared to Sandy Bridge. 2600Mhz seems easy. This should be fun.

This concludes the processor part. Did I miss anything relevant? I have overly simplified a lots of stuff. So if you have any question, please go ahead…

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3 Responses to The right processor

  1. This comment has been removed by the author.

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  2. Hi Javed,

    Thank you for the articles detailing rationale behind selecting right computer hardware. Those really helped me thinking out appropriate PC components that I should purchase.

    With all that said I'm kind of still not sure on the CPU that I should go for whether a 3930K (& ASUS P9X79 Deluxe) or 3770K(yet to decide on Motherboard). So let me list out my primary usage of the yet to purchase system and if you could suggest appropriate CPU & Motherboard it would be great help. I intend to run 4(max 5) virtual machines comprising of Win2008ServerR2 as their OS on all VM's. 3 VM's with SQL Server 2012 and 1 with SharePoint 2010.

    -Samrat

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  3. Go with X79 platform. Get loads of RAM :-)

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