Summary: Some musings comparing work accomplished by my computer to my personal out-of-pocket costs for the electricity to feed it 24-hours a day - something I dare say very few home computer users look at.

Last month I upgraded a Celeron D 2.53GHz media server to a Core 2 Duo 1.8Ghz. When not using the server for "media" (watching DVD or recording broadcast TV), I run BOINC/Rosetta distributed science jobs on it. Since the Celeron D was functional, I moved it to an old chassis & updated the power supply - both have efficient, after-market power supplies. I now have 2 systems running 24-hours a day.

As a hobby (and part of what my Mother would call our inherited Scot's blood) I enjoy using an AC power meter to evaluate the cost of running appliances. My meter is from http://www.brandelectronics.com/ and it shows some interesting facts, such as that my Cox digital cable box consumes 24-watts when powered "ON" ... and 23-watts when turned "OFF" :-) Gives the concept of "off" a new meaning.

Obviously, the Core 2 Duo - running 2 jobs at once - contributes more credits to BONIC projects than the Celeron D. But I was interested in comparing what I gain given the monthly costs to run my now unnecessary Celeron D.

Computer Summary:

Core 2 Duo: 1.8GHz, 1GB DDR2-800 RAM, 320GB SATA drive, nVidia 7100 (fanless) 400w power supply
* Rosetta Benchmarks; fp=1744 int=3656 (since dual, means maybe fp=3488 int=7312)
* When Idle: CPU temp = 70 DegF, AC power usage = 105 watts
* When both cores at 100%: CPU temp = 100 DegF, AC power usage = 129 watts

Celeron D: 2.5GHz, 512KB PC2100 RAM, 30GB PATA drive, nVidia 6300 (fanless) 350w power supply (it had 1GB RAM, but 1-of-2 sticks went bad)
* Rosetta Benchmarks; fp=764 int=1677
* When Idle: CPU temp = 100 DegF, AC power usage = 98 watts
* When sole CPU at 100%: CPU temp = 125 DegF, AC power usage = 134 watts

I was at first pretty shocked that the Core 2 Duo - even with both CPU at 100% - used less total wattage than the Celeron D. Especially since every time you pick up a computer magazine there are dire warnings about needing a 600w, 800w, or even 1000w supply in a "modern" computer. By the way, a good AC power meter also tracks maximum power - which turns out in my case to be from 140 to 150 watts max when either the Core 2 Duo or Celeron systems first boot up.

Since both systems eat about the same power, just rounding the wattage to 130 watts burned 24-hours per day amounts to from $7.50 to $13.00 per month. This ranges includes my Minnesota kwh charges of about $0.08 per KWH and also my California charge of about $0.14 respectively. I wonder how many people understand they pay that much per month to run their computer 24-hours a day? Over a year that totals from $90 to $160 per computer - and this is JUST the computer. I'm not including the wattage used by monitors, printers, Ethernet switches or the DSL/cable router hardware. Plus with the computers running in a cool Minnesota basement, I don't have to include the extra air conditioning load they'd create in a hot climate like my Southern California home. (I am an engineer spending time in both states)

So now for the true "musing" - if I average the last 10 Rosetta jobs handled for each computer:
* Core 2 Duo: average 10594 seconds and 36.87 credits granted per job
* Celeron D: average 10406 seconds and 22.75 credits granted per job

However, since I'm looking where my $7.50 (or $13.00) per month goes I have to remember the Core 2 Duo runs 2 jobs at once for this same wattage so really one could say I am "paid" an average of 73.74 BOINC credits for each pair of 10600 second jobs that the Core 2 Duo runs. So the Core 2 Duo gives me almost 4 times the BOINC credits for the $100 spent a year on electricty to feed my hungry computer. Of course, even if the CPU throttled back to idle I'd still be paying about $80 per year to run the computer 24-hours per day. So Rosetta really only 'costs' me the extra $20 per year.

So should I still run the Celeron D? Should I upgrade it to something closer to the Core 2 Duo? The upgrade cost me close to $450 once one considers the cost of the CPU, new motherboard, and new DDR2 RAM. This is an interesting question without a simple answer ... yes, running the old Celeron D doesn't cost me any more from a buying-hardware stand-point ... but I am paying good money out of my pocket for the power.

So what is the real cost of power?

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the P4 Celerons are probably the worst CPU for BOINC in terms of processing per watt - the C2x CPUs are the current best bang per Watt I believe, so if you could upgrade then that would be beneficial to the project (plus its slightly reduced electrical consumption in absolute terms) but of course we can all only give what we can afford, and the Celeron's output is appreciated too! ;)

If you were to consider upgrading/replacing the Celeron then you can factor in the value of those components for resale (i.e. ebay), and you already have the case, PSU and HD.

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the P4 Celerons are probably the worst CPU for BOINC in terms of processing per watt - the C2x CPUs are the current best bang per Watt I believe ...

Yah, actually, just this morning I was checking out prices on newegg for a dual-core slightly less than leading edge. A older AMD dual-FX with 1GB DDR667 and uAtx mobo is only $239 total.

At work I have 2 x A64 2.0 GHz doing Rosetta when not running regression tests and they easily slightly top one of the Core 2 Duo's 1.8Ghz cores in the benchmarks. So I am thinking to just split the difference a bit and go with a slightly less state-of-the-art upgrade.

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...I was at first pretty shocked that the Core 2 Duo - even with both CPU at 100% - used less total wattage than the Celeron D. Especially since every time you pick up a computer magazine there are dire warnings about needing a 600w, 800w, or even 1000w supply in a "modern" computer. By the way, a good AC power meter also tracks maximum power - which turns out in my case to be from 140 to 150 watts max when either the Core 2 Duo or Celeron systems first boot up. ...

Your AC power draw may well peak at 150 W max, but remember that the power supply contains massive capacitors that serve to buffer spikes on the load. The powers supply may well be delivering well over that 150W for a fraction of a second here and there, especially during startup.

If the Voltage on any of the DC lines drops by more than a few percent for even a few milliseconds modern motherboards will power down as a protective measure.

In short, your AC meter does not disprove the computer magazines suggestion of having a supply that is rated at a few times the apparent peak AC usage. If you are the kind of person who never upgrades a computer after purchase, like I am, stick to the lowere end of the range of their advice, on the other hand if you are the kind of person who is always adding more fans, graphics, etc etc (like my son), then go for the higher end of the computer mag suggestions.

Do not go below the bottom end of the suggested range unless you are the kind of geek who can cope with trouble shooting when the board refuses to boot, or spontaneously cuts out, and also have a selection of higher rating power supplies to swap in. Trading in a used low rating PSU for a higher rating one could cost more than the electricity you were trying to save. Hence the magazine advice is good advice to their readers.

Secondly, choose a power supply that is efficient and especially one that draws almost no AC power when it is delivering no DC output. The reviews on PSU efficiency are rather rare - I have seen just one in the last year in UK mags but maybe Google can help here. Especially for a BOINC box that is on 24/7 it is saving money on the heat put out by the PSU itself.

So what is the real cost of power?

Dpends on where you live. As you say in summer in hot places the cost of power is increased by the increased cost in Air Conditioning. In contrast, I run old inefficient boxes all winter as the power used heats the lounge, which in my case would be heated by electricity anyway - so the power cost is zero.

(Actually it is not quite zero, as I would not leave my lounge heated all night, but you get the point). (And it is easier to get out of bed knowing that the lounge will be warm)

If you heat with gas, then you need to discount you winter power usage by the cost of gas heating saved, and so on.

What I have done is to work out the cost of running my old boxes all summer (no air conditioning). In two years continuous, or in about four years of summer usage, the power used by 10 boxes each of 866MHz will pay for a single AMD box with dual core 4200, ie giving about the same nominal output in one box as the ten old boxes. So the plan is to buy the new box, and run the farm only in winter.

My suggestion to you is similar, and more so in your case as you have air conditioning to think about. Only run the main box in summer, but as soon as you turn on the heating, switch that Celeron back on and leave it running 24/7 all winter. Turn it off with the heating in the Spring.

Just a suggestion of course...

R~~

Yah, actually, just this morning I was checking out prices on newegg for a dual-core slightly less than leading edge. A older AMD dual-FX with 1GB DDR667 and uAtx mobo is only $239 total.

At work I have 2 x A64 2.0 GHz doing Rosetta when not running regression tests and they easily slightly top one of the Core 2 Duo's 1.8Ghz cores in the benchmarks. So I am thinking to just split the difference a bit and go with a slightly less state-of-the-art upgrade.

The X2 might get a better whetstone and dhrystone score (more likely whetstone because of the strong AMD fpu), but in real world throughput the C2D is a fair bit quicker at the same clock speed - although the claimed credits might be similar, or even higher on the x2, the granted credits will generally be higher on the C2D. Also, if you're thinking of overclocking, the C2D has a lot more headroom - especially the 1.8GHz ones - you can generally run them at over 3GHz quite happily.

HTH
Danny

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There's a really good PSU guide here:
http://www.silentpcreview.com/article699-page1.html

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... The X2 might get a better whetstone and dhrystone score (more likely whetstone because of the strong AMD fpu), but in real world throughput the C2D is a fair bit quicker at the same clock speed ...

Which real world? Quicker for what?? There are many 'real worlds' for cpus.

If you are running mainly windows office type apps, then what you want is a cpu optimised for integers & message handling.

If you want to run games then you want a cpu optimised for handling the parts of the graphics that the graphics card leaves out

If you want to run BOINC then you want a cpu optimised for scientific/numerical work.

For example, as something I was looking at recently for a friend: the Via C7-M is great for the first of these categories compared to the Pentium-M at the same speed, but for the last of these categories the C7-M sucks (as it is not good at handling out-of-order pipelines, which the Pentium-M is particularly good at for a low-power chip).

Looking at overall benchmarks is misleading as there is no one 'system performance'

So (unfortunately) are the traditional BOINC Whet and Dhry benchmarks misleading, even for assessing the speed a cpu will run a 'typical' BOINC project -- that is why the old credit algorithm was so variable even without people cheating. And that is why the Whet / Dhry bencmarks are totally off the real world even for BOINC.

If you are buying specifically for BOINC choose a cpu / system with good benchmarks for scientific computing, or ignore the benchmarks altogether.

River~~

There's a really good PSU guide here:
http://www.silentpcreview.com/article699-page1.html

Thanks Danny.

This is a good example of what I meant. It is a great review for people looking for a quiet PSU (in fairness that is what the site is all about), and a good review of quality.

What it does not do is tell me how efficient any of the supplies is. What I want to see is the AC power draw for each PSU at a standard 80W and 200W DC delivery, or (what is equivalent) the %efficiency at each of these as a number, not as 'pretty good' etc. (%efficiency = 100 x DC Watts drawn by motherboard / AC Watts drawn from wall)

If I am going to use the PSU on a machine that is boot-on-LAN, I also want to know what the PSU's AC power draw is when only powering the LAN components. It is part of the ATX spec that a board will power down most of its components while waiting for boot-on-LAN, but there is nothing in the spec that says the PSU has to draw any less power from the wall! Here %efficiency is less useful, as the real issue is how much power the PSU draws as overhead when delivering next to nothing - like Lynn's example of 'a whole new meaning to "off"'

Without that info, I can't compare power costs between two PSU's.

It is quite hard to find this info -- both online and in magazines the writers assume (probably correctly) that this is not what most of their readers are after.

R~~

@Lynn, nice analysis.

I should have said:

... The X2 might get a better whetstone and dhrystone score (more likely whetstone because of the strong AMD fpu), but in real world rosetta throughput the C2D is a fair bit quicker at the same clock speed ...

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There's a really good PSU guide here:
http://www.silentpcreview.com/article699-page1.html

This is a good example of what I meant. It is a great review for people looking for a quiet PSU (in fairness that is what the site is all about), and a good review of quality.

What it does not do is tell me how efficient any of the supplies is.

Try clicking on the "review" link of the PSU. The ones I checked had a table of efficiency vs load on the last page of the review.

My electric bill shows last year and this year comparisons. I can say that I am paying only about $5 a month more to leave my computer on all the time running Rosetta. I have an AMD 2400+.

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Hi Lynn:)
I like your musing on power consumption of your computers. I too am interested in power cost. Over the last 8 months I am running 4 computers (2 with dual core processors and 2 w/ single processor) 16 hrs per day crunching rosetta@home projects. I reviewed my power bills on the same period of 8 mos. before volunteering for rosetta projects and compared it with the 8 months I was crunching rosetta projects. My monthly electric bill increased by $21.00 per month average. I am a computer geek. So, I just add $21/mos to my monthly operating budget.
I am planning to revamp my single processor computers and replace the MB and CPU with dual core processors.I will try getting a MB ready for QUAD processors.
I like your comparison of power usage between the single core and the dual core processor. That makes my decission to upgrade soon.
joseps

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I turned off my 5computers when I went on vacation. When I return today, I can not upload work. Need work units to run computers.
joseps

There's a really good PSU guide here:
http://www.silentpcreview.com/article699-page1.html

...

What it does not do is tell me how efficient any of the supplies is. What I want to see is the AC power draw for each PSU at a standard 80W and 200W DC delivery, or (what is equivalent) the %efficiency at each of these as a number, not as 'pretty good' etc. (%efficiency = 100 x DC Watts drawn by motherboard / AC Watts drawn from wall)

If I am going to use the PSU on a machine that is boot-on-LAN, I also want to know what the PSU's AC power draw is when only powering the LAN components. ...

Hi Danny,

I owe you an apology.

The site you pointed to *does* have all that info, just not on the overview page. By clicking on the review link for each PSU it is all there, the boot-on-LAN figs being shown as +5SB (ie standby).

Thanks for the link and sorry for my initial obtuseness.

River~~

Hi Danny,

I owe you an apology.

No apology needed! ;)

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