power efficiency of older macs

[p.amadeus]

Does anyone know of a resource which lists the power efficiency of (older) macs?

everymac.com doesn't have this information.

also, if anyone does know anything about this - does the power supply play a bigger role in this or is it more strictly based on the specs of the system (aside from the power supply) as designed by Apple?

 

[Christopher]

Does it matter really?

 

[p.amadeus]

I'm curious...

 

[redrouteone]

I've wondered about this lately my self. I've been thinking of picking up one of those Kill-a-watt meters.

Our electric rates here are fairly high so every bit counts.

 

[wood_e]

http://www.info.apple.com/support/applespec.legacy/index.html

 

[p.amadeus]

what I'm wondering is if it would be feasible to replace the power supplies in classic macs with more modern/efficient ones to reduce power usage. Obviously this would require some hardware hacking and may not be pretty in some cases, but it still may be worth investigating at least for classic Macs with larger size cases that modern power supplies could be retro-fitted into.

 

[tomlee59]

Although I've not made direct measurements on these particular power supplies, they are all switchers. At moderate to heavy loads, switchers typically have efficiencies of 80-90%. Modern ones are not that much better. If the supply is delivering 100 watts, say, then it's pulling perhaps 120W out of the mains. If the supply were 100% efficient, at best you'd save 20W. Of course, real supplies aren't perfectly efficient, so let's split the difference and postulate that one might be able to save 10W by upgrading to a better power supply.

If you compute the savings over one year, assuming these numbers, and assuming 100% on-time, we're looking at about 90kWh saved each year (let's call it 100kWh). I don't know what electricity costs in your area, but let's say it's as high as 20cents/kWh (about twice the US national average). In that case, the annual savings is about $20 for this assumed scenario. And if the computer has any sort of a low power mode, or if the computer isn't on all the time, then the savings will be correspondingly diminished.

 

[MacMan]

Mactracker has power information under the Expansion/Ports tab. The power usage given is generally the maximum during high-load situations, normally the machines will use less.

 

[Anonymous Freak]

Well, the best of modern PC power supplies are about 85% efficient. That means that 85% of the wall AC power gets converted into DC power for use by the electronics. Older power supplies tended to be about 60-70% efficient, so you had more waste in the power supply. However, for completely closed systems where the manufacturer knows the absolute maximum wattage that will ever be drawn (like the Mac mini, or the older compact Macs,) you can achieve higher efficiency by designing the power supply for EXACTLY that wattage.

The modern "85% efficient 1000W" power supplies are only 85% efficient at close to their top draw. Which means that if you put one of these 1000W power supplies in a standard system, that will only draw 100-200W, you are going to be very inefficient.

If you're talking about efficiency in terms of 'performance per watt', then old systems are impossibly inefficient. While a 40 MHz 68040 may only use 5W of power, compared to an ultra-power-hog 3.6 GHz Pentium D at 150 W, the 3.6 GHz Pentium D is many orders of magnitude faster in performance that more than makes up for the higher power usage. Not to mention that all the other components in the older system are likely drawing almost as much power as the equivalents in the new system. So a choice between a 40 MHz 68040 drawing 95W at the wall and a 3.6 GHz Pentium D drawing 250W at the wall is really no comparison. And if we use a new Core 2 Duo instead of a Pentium D, the delta is even greater.

Just think: A PowerBook 190 and a MacBook Air have the same wattage power brick.

 

[tomlee59]

what I'm wondering is if it would be feasible to replace the power supplies in classic macs with more modern/efficient ones to reduce power usage. Obviously this would require some hardware hacking and may not be pretty in some cases, but it still may be worth investigating at least for classic Macs with larger size cases that modern power supplies could be retro-fitted into.

So, to answer your question directly, what you propose would be possible, but the larger question is whether or not it's worth the effort. The calculations I offered show you roughly what the magnitude of savings could be. We're likely talking dollars saved per year, not hundreds, so if you're doing a purely economic analysis, the savings seem hardly worth it. Most of the power taken from the wall really does make it to the computer; only a small fraction is wasted by the power supply.

If you're thinking more along the lines of "think globally, act locally; every little bit helps," then the "ROI" analysis involves other considerations.

 

[p.amadeus]

thanks for all the responses.

I guess it wouldn't really be worth undertaking unless you had a lot of older macs you kept running 24/7.

just a random passing thought of mine

 

[Charlieman]

The beige G3 is the only vintage Mac that I have tested with a (quality) socket based power meter. The G3 base unit draws about 60W, which was about 20W less than a PII or PIII PC with the same PSU.

I have done a lot more testing with modern PCs (part of the evaluation process when tendering for new models). This week I looked at an old P4 (on an 845 chipset motherboard) and a brand new Intel 6550 processor (on an Intel DQ35JO board, a standard for corporate PCs). Both had similar expansion capacity, similar PSU specs and both drew about 60W. Coupled with a 19" TFT monitor, the contemporary PC draws 90W total.

All of this is fresh in my mind because, last week, an IT director brought up the old chestnut that "a PC can cost more in electricity than the initial purchase price". The cost of running a PC drawing 90W continuously for four years is £240 (based on UK electricity price for a big customer, but ignoring night use rebates). PCs are cheap, but I can't buy anything useful for £239.

For anyone buying lots of PCs for a large electricity user, make sure that your new PCs have PSUs with active power factor correction (active PFC). If you use a lot of electricity, you get billed for "out of phase" power use, which can be a significant cost if your PCs use passive power factor correction. In the US there is a government programme promoting adoption of active PFC PSUs, which will no doubt rub off on PC specs internationally. (Don't worry if you are a home or small business PC user: you won't be charged for "out of phase" power consumption.)

I generally agree with Tom Lee regarding the economic/environmental benefits of updating PSUs in vintage Macs. However, you may wish to fit a more modern PSU to computers that are being used as a server: not for energy efficiency reasons, but to provide reliability and safety.

Some interesting questions arise from this thread. If I wished to provide a web server running from home for a few friends, what would be the best (in energy terms) vintage Mac hardware? For a server delivering dynamic content, it has to be a PowerMac, probably a headless G3. For static pages, an LC475 will be cheaper to run than any PowerMac and only marginally slower.

 

[II2II]

A couple of comments:

The best way to save energy/money is to simply buy a powerbar with a physical power switch then turn everything off when it is not in use. Perhaps my power meter is wonky, but I've been measuring ghost loads that are between 10% and 30% of peak power use on some machines (worse case was an original Apple IIc at over 60% IIRC). At the 10% end of the spectrum, a computer that is used two and a quarter hours per day (or less) would use more power for the part of the day that it is turned off than turned on.

Of course you cannot do that with machines that have to be up (e.g. servers). There are a couple of cases here though: if it is a personal use thing and you know that it is unneed while you're sleeping or at work, machines with software controlled power supplies can usually be turned on or off according to a schedule. While the earlier comment on power use to performance ratio is true, if you are not using the machine to its fullest capacity you may find that a computer with a slow processor and low power consumption will do the job just as well. A static web server was already 5Abrought up, word processing and file servers are other obvious ones, Even graphics work can be done on less power hungry models (if you go with more modern hardware).

Some porblems just require a social solution (modifying our behaviour) rather than a technological one (more energy efficient devices).

Granted, I've contemplated building my own power distribution system too to cut down on the few watts left on my discretionary power usage (i.e. computer energy use).

 

[Charlieman]

Triple ][: Can you describe the "ghost load" in more detail. I'd like to know more about devices (whatever the age) which are inefficient in standby. The IIc PSU is obviously of interest here.

John Dvorak (and I know that many people will be spitting with contempt on reading the name) recently wrote a very well argued column about power management. He simply said, "If not in use, turn it off completely". Dvorak is paid to be a stirrer but that does not necessarily mean that all of his contrary ideas are ridiculous. Don't run around switching off mobile phone chargers and their like; just switch off devices like computers and lights bulbs that draw lots of power.

 

[SiliconValleyPirate]

Many people can't see past some of Dvorak's stirring and ranting, he's actually a very well grounded and sensible person with a very non-sensational outlook on everything technological or otherwise. I should also add that while he is a paid journo, a lot of the stirring he does is purely for his own and other's entertainment, especially on the subject of Apple. He's not anti-Apple, he's like me he just loves upsetting the fanboys and watching them all wet their diapers, in the process revealing what a bunch of boneheads they all are. [] ]'> You only have to listen t ohim on TWiT when everyone is raving about something pointless, he'll just butt in and say 'oh who cares, it's all BS'... and he's usually right [] ]'>

Anyhoo, yes. In my room/office I have a smart power strip behind my desk that senses the load on the first plug on the strip. If the load drops below a certain level it shuts all the sockets off.

I have my stereo amplifier (hard-switched and draws a pretty constant load) on the 'master' socket. When nI sit down at my desk I most often put music on so I switch the amp on when I'm there, and off when I leave. That shuts off all the other non-critical equipment in my room at the same time, but means I can turn it on at will whenever my amp is on. If I need to leave any of it on I leave my amp on. Needless to say I stocked up on CMOS batteries for the PCs that are on the auxiliary side of the power system. All the Macs on there have dead PRAM batteries anyway so that hardly makes any odds [] ]'>

dvorak.org/blog !!!!

 

[Quadraman]

"The beige G3 is the only vintage Mac that I have tested with a (quality) socket based power meter. The G3 base unit draws about 60W, which was about 20W less than a PII or PIII PC with the same PSU. "

More powerful than a contemporary PC and uses less electricity? Yay for Mac TCO!