Common misconceptions of x86 vs ARM

I see a LOT of misconceptions of the x86 vs ARM debate, and I would like to debunk a few of them today.

1. x86 is inherently more power hungry than ARM

False. This is a common belief, but it is not true at all. Yes, commonly x86 chips consume more power than ARM chips. However, the issue is, even the lowest end Celeron chip outperforms all the Snapdragons, Tegras, and OMAPs. Sure, Intel's chips consumes more power in most cases. However, truth is, it is simply because even the lowest end x86 chips are more powerful than ARM chips.

When the performance is comparable, there is little difference in power consumption between x86 and ARM. Take the Motorola Razr I and the Motorola Razr M. These two devices are practically the same phone. The only difference is that the Razr I uses an x86 chip, whereas the Razr M uses an ARM chip. Performance between the two is comparable. And battery life is comparable.

ARM chips use more power when their performance goes up. I would not be surprised if ARM no longer has a power consumption advantage when ARM chips go up in performance.

DL;DR version: ARM uses less power simply because it has lower performance.

2. ARM gets more performance per watt. This is a point that is commonly raised, but to be honest, there is little actual factual backing behind it. Sure, ARM chips usually do consume less power, however, that does not mean that ARM chips perform better per watt. remember, performance per watt = performance / wattage.

As we have already established earlier, x86 chips have comparable performance at the same power consumption levels. This means that performance per watt between x86 and arm is so small that it is generally ignorable.

I would actually argue, that x86 has better performance per watt. A Xeon E3V2 chips draws around 69w of power. yet it can easily outperform any combination of ARM CPUs whose combined power consumption is 69w.

TL;DR: x86's performance per watt is at least as good, if not better, than ARM.

3. ARM is taking the server world by storm

Ok, this is the most ridiculous one, by far. If we look at the compositions of the server market, on the super high end, you get the IBM's running PowerPC and the HPs running Itanium. Than, a bit lower than that, you get the multi Xeon configurations of E7s and E5s. A bit lower than that you get the single Xeon, single Opteron configurations. Even lower than that, many datacenters would rent you consumer grade Core I powered Servers, and on the bottom you would get the Atom servers.

Realistically, ARM chips only stand a chance competing against the bottom rung Atom servers. However, even then ARM has a lot of trouble competing. Current ARM chips can support no more than 4gb of ram. Popular ARM chips like the NVidia Tegra 3 can only support 2 gb.

Other than that, there are still many hurdles to cross. The world's most popular server operating systems Windows Servers and Red Hat enterprise Linux/Cent OS do not work on ARM. ARM is much worse in virtualization and encryption. ARM chipsets do not have the IO support of comparable x86 chipsets.

Most importantly, the category that ARM is going to go into is a dying category. the "bottom end" small, lower powered servers are disappearing, getting replaced by virtual machines. Also, are there eve any ARM servers on the market right now?

TL;DR: ARM is not taking the server market by storm.

Edit: Regarding points 1 and 2: First of all, lets assume that the Razr I and Razr M have similar performance and battery life. As we know, both devices share the same screen, speakers, etc. Thus any difference in performance must come from the difference in the SOC. One is Atom based, the other is snapdragon based. Razr-i-battery_medium




Since we are working with the assumption that they are roughly equal in performance and battery life, my point actually can be reinforced. Current generation Atoms are 32nm, whereas current generation Snapdragons s4s are 28nm. Thus if the Atom manages to deliver the same performance at the same battery life on an older process, it means that x86 actually manages better performance per watt.

PS: anyone know of any other devices like the Motorola Razr I and Razr M? Devices that are the same just with a different CPU/Chipset combo?