Blogs Are low-power desktop CPUs worth buying?

You've basically covered it all in your blog there.

I've considered low-power parts before, when the question was about running a HTPC passively, but besides that it's not worth thinking about it really.

When you use a 65/77W CPU in your normal rig, then it'll run clocked down (speedstep) anyways while browsing, writing a document or watching a film, and in that case you save just as much power as with a low-power part.

 

I'm running a second gen i3 in my younger brothers desktop which is on about 14 hours a day, had complaints about processing power but it hardly registers on the bill which is nice

Comes down to what you need and investment up front or pay more over the long run

 

Gpu is missing from calculations... average mid range pcs will draw 250w (including decent monitor). That is 1/4th the power draw of vacuum/kettle/hairdryer.

Of course the real question is, is an under utilised CPU just as efficient as it's low voltage breatheren (how games acutally put the cpu to 100% usage in all areas of the cores)? The only way to know this is for bit tech to do some benchmarks on the T series and let us know the power difference and fps difference, and then do a comparison on cost.

I'll stop rambling, its late. :>

 

...but all my cpu power means slightly less heating required (except on the 30 warms days/year) so it's not wasted energy

 

The biggest issue i see is that we are comparing TDP instead of real power consumption. The problem is - TDP doesn't mean anything. For example take a look at i5-2400 vs i5-2400S vs i5-2400@i5-2400S voltage comparison :
http://www.silentpcreview.com/article1202-page3.html
Even at stock voltage and higher performance, we talk about 14W difference between a 65W TDP i5-2400S and 95W TDP i5-2400. Real power consumption difference is less than a half of the TDP difference. And because we can assume their test system used ~30W (considering the specs of the system), that means power consumption of CPU alone would be 59W at load for i5-2400S and 73W for i5-2400. Sure, there is a difference, but even the 73W value is so close to the 65W TDP that it makes no real difference.

This is the reason for only limited list of options for these power saving CPU - they are selling them only in case the original CPU was already very close to the lower TDP limit. That is why you got Pentium G620T (35W) vs Pentium G620 (65W) - the standard G620 will likely use something like 40-45W, so at expense of lowering clock they shaved off that few watts.

At least in case of Haswell they got a bit more creative and they actually did something more than that - i7-4770S is still the old style "we are close, so we lower the clock speed a bit" type, but i7-4770T with 45W TDP is actually more like the laptop style CPU - very low standard clock speed (2.5GHz) combined with very high Turbo multiplier (3.7GHz) - by high i mean +12 instead of typical +5/+6 you find in desktop CPU.

So my opinion is - if the CPU is only one TDP category lower than the original version, then it is not worth to invest in them, because the original version is probably only few watts above the TDP limit of the "power saving" version. If the CPU is two TDP categories lower, then it is worth thinking about it, as you usually compromise only at long term multicore performance, the TDP is good enough for short bursts of single or dual core performance.

 

I think you've missed something. The low power CPU will hit 100% load before the higher power counterparts meaning they won't be at 100% when the low power one is. So it will only cost you more if you were to go over that 35W CPUs full processing power capability on the higher power CPU.

 

No, not for home users.

 

I was talking about 100% use of both power saving and normal CPU. Sure, the power saving one will complete the task slower, my point was that it makes no sense to consider power saving CPU just because of the cooling, as usually you will see differences like above - 59W power use of the power saving CPU with 65W TDP, and 73W for non-power saving one. Both are very close to the claimed low power TDP, just on different sides, while the non-power saving is very far from his own claimed TDP.

So that rules out the use case scenario of "must buy power saving CPU because of passive cooling", and then comes the rest, which is again not simple, because while the higher TDP CPU consumes more power, it does the task more quickly, so it is possible that the higher power TDP CPU will actually consume less power over time compared to lower TDP CPU. In idle the power consumption is identical for same generation of CPU.

The only use-case scenario where i could see this making difference is 24/7 folding, but people usually don't buy power saving CPU for that.

 

Good article, but it's too bad that you did not put REAL results. while it's nice to know about the comsumption cost, I do not see any performance comparison nor heat under idle/load.

Let's see those test from a french site specialized in "eco friendly tech" :

- i7 3770T (4C/8T - 2.5GHz, 3.7GHz turbo - HD4000 - 45W) :

http://www.ginjfo.com/dossiers/test...ces-dun-core-i7-2600k-sans-les-watts-20120427

- i7 4765T (4C/8T - 2.0GHz, 3.0GHz turbo - HD4600 - 35W) :

http://www.ginjfo.com/dossiers/test...swell-chaque-watt-au-plein-potentiel-20130807

The last link is in fact a i7-3770T Vs i7-4765T Vs i5-4670K, all without discrete GPU.



They are really capable CPUs, even for ethousiasts. Lets face it, not all of us do 3D rendering or atomic simulation at home. Now, I agree that it's a little power saving when you have an high end GPU, but for those with HD7750 like or even only the IGP it's a lot (35W vs 84W for an Haswell i7).

I'm currently running a Q6600 (4C/4T - 2.4GHz - 105W) with 2.0V DDR2 stick @800MHz (4 stick) and a Geforce9300 IGP ... the move to an i7-4765T will save 70W on the CPU side while doubling the performance (and it has a better IGP included in the TDP). The use of 2x 1.25 Lovo DDR3 will save lots of power compared to 4x 2.0V ... take a look at your own review

http://www.bit-tech.net/hardware/memory/2010/03/18/kingston-lovo-power-saving-1-25v-ddr3-ram/2

In the end, for at least 2X more performance I'd save 82W of CPU + IGP side (70W from Q6600 + 12W from Gf9300) + 20W (approx) from the memory (Kingston Lovo at 1.2V). If I add the move from mATX to mITX and replacing the 160GB HDD buy an SSD ... then it's another saving. For home / development / Sketchup and light gaming (read 2D gaming) it'll be a great rig. Two times the performance for less than half the power usage .... and if I need offload computing (3D rendering), I'd go the ARM farm route.

 

In UK avg kwh is 8-10p + charge, not 15p.
(have yet to find an open contract to pay by Kwh like used to be last year, all now need a standing charge).

 

Why not swing both ways and underclock?
@Panos in NI its 17.5p per unit. Nice to be about double the average. Who is getting power in the UK for so cheap?

 

I pay 14.76p per daytime kWh in Southern England, (with Atlantic Electric and Gas) - that's with a standing charge on top, (26.1p per day). They were the second cheapest around when I joined. I've past the lock-in period and am ready to switch, so if you can tell me who charges 8p per kWh that would be great.

I do pay 6.9p for night-time energy, but night energy only makes up less than 18% of my usage - seeing as I generally sleep at night...

 

While I am a computer enthusiast, I honestly could give less of a crap about getting the best performance possible, and it boggles my mind how people will only buy a CPU for it's performance rather than it's REAL selling points. When you build a system with an i3, you're doing it because you're looking for something power and heat efficient; price and performance are not the i3's selling point (price belongs to Pentium/Celeron, performance belongs to i5/i7). When you buy something with a specific intention in mind, the other downsides should not matter to you. You can't have the best of all worlds.

This is why Intel's Atom and AMD products in general suffer in the enthusiast market - people strictly look at how it performs, dismiss everything else, and decide they're bad products. Are AMD CPUs worse? Yes, but you're not looking at the selling points - AMD has a good record of backwards compatibility between generations, significantly cheaper products per-core, and in most everyday situations they get the job done fine. AMD is not by any means the best choice if you're looking for top performance or power consumption, so when you act like those are the only 2 things to consider, they look terrible.


As a side note, people today really take for granted that everything is instantaneous. Turn on your best rig from 10 years ago and see how much it can handle of today's stuff. Custom-made computers from 10 years ago were fantastic for their time and nothing you'd have been disappointed about. If you're the type who thinks AMD overall sucks and anything worse than an i3 is too slow for you, maybe you should just consider that waiting an extra second or 2 for something to work doesn't mean the platform is bad, it just means you're impatient and spoiled.

 

Rep jizz for that, mate ! I've discovered computing when I was 8yo. Back then, CPU where cuminating at around 7MHz, had no HDD and floppy drives transfer rate where around 240 Kbits/sec. I've learnt to wait.

I remember that my real-time programming teacher said : "Real time doesn't and will never exists. Everything take time, even if it's very quick". Now, people want everything and want it immediatly. Maybe I'm mistaken, but we are not ALL astrophysicians who need HPC at home. I can wait a little when I do 3D rendering. When I was studying 3D, CPU where only single cores (Athlon XP2000) and 3min of animation was taking a month to render 24/7 .... so if a 35W low power i7 does it in 2 hours vs 1h30 hours for the full fat 84W one, I CAN LEAVE WITH IT !

My wife's dad use a pentium G620 with no discrete GPU for family video editing and encoding. Sure it's not as quick as an i7 ... but while it's encoding, he's taking care of his garden. That's real life multi-tasking

 

Floppies, they were quick. Compact Cassette on other side... 3-4 minutes for 48k program, now that needed patience. And only if the tape was read correctly and it wasn't damaged .

I downgraded my laptop from 1400€ Acer Aspire S7 (Core i5 ULV, SSD) to a Acer Aspire V5-131, which has only Celeron 1017U. Sure, i upgraded it to 8GB RAM and added my good old X25-M G1 80GB, but after that, there is really not that much difference. Sure, the i5 has Turbo, Hyperthreading, bigger cache - but in reality it doesn't matter for majority of tasks. Even the compilation doesn't show too much difference because nearly everything these days does incremental compilation - so if compiling a Java class takes 0.1 vs 0.12 seconds, it makes no difference to the user.

 

According to this...
http://www.energysavingtrust.org.uk/Energy-Saving-Trust/Our-calculations
Standard rate Electricity = 15.32

Also backed up by...
http://blog.comparemysolar.co.uk/electricity-price-per-kwh-comparison-of-big-six-energy-companies/
Average price of 15 pence per kWh.

And a break down done by the government on averages for selected towns and cities (Table 2.2.3)
(Warning PDF)https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/65940/7341-quarterly-energy-prices-december-2012.pdf(Warning PDF)
also says the average is 15.32

 

I'll go you all one better. I have an actual HPC setup here, a quad socket AMD board with 4 HE processors (8347HE.) Under full tilt, it takes what my wife's i5 does, before I add the GPU in. GPUs, of course, making all the difference in the world here. HE here means something. For desktops, not so sure, but when you pack a bunch of CPUs together (this is 16 real cores, mind) it certainly matters that I can cool these passively.

It's planned to heat the living room in the winter months, to save on power-we don't use the heat any more, we use our new fireplace and PC waste heat. Saves us LOTS.

 

Haha I've done something similar. While I don't think a single computer can generate enough heat to effectively fight against the cold of winter, they are good for warming a concentrated area. My hands get cold and I once modded a desk where I cut a hole in the keyboard tray for a motherboard tray to go, and then rotated the tray so the CPU would be just below my hand. I used the heat from the CPU to warm my hand.

 

The difference will be even less, if you take into the equation, that the low-power CPU will use less power pr second, but will keep on working for more seconds to get the job done.

I wonder if it is the same way as with other forms of energy-consumption: A certain task demands a certain amount of power to be executed, no matter what way you choose to execute it.

I.e. It will take the same amount of calories ot watt to heat a specific room to a specific temperature, regardless if the heater is a 100 W or a 500 W one.

Just my 20 cents