Date: Sun, 02 May 2010 03:58:36 +1000 From: David Rawling <djr@pdconsec.net> To: freebsd-questions@freebsd.org Subject: Re: ziz a dumb question? Message-ID: <4BDC6BCC.1@pdconsec.net> In-Reply-To: <20100501155543.f909c863.freebsd@edvax.de> References: <20100501015705.GA46858@thought.org> <20100501041913.81a34394.freebsd@edvax.de> <20100501030350.GB46985@thought.org> <20100501052055.9def3399.freebsd@edvax.de> <4BDC09A8.4030405@onetel.com> <20100501155543.f909c863.freebsd@edvax.de>
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On 1/05/2010 11:55 PM, Polytropon wrote: > On Sat, 01 May 2010 11:59:52 +0100, Chris Whitehouse<cwhiteh@onetel.com> wrote: > >> Seriously? Or joking? How did you measure it? >> > Well... erm... in fact... I didn't measure anything, I just > utilized the numbers. :-) Modern PCs come with a 700 W power > supply (and more), and the specs for my AS/400e 9406-170 say > 654 W with expansion unit (326 W without), measured kVA values > (according to manual) are similar. Weight is 70.5 kg, and > size is two big towers side by side. > You seem to be assuming that a desktop PC draws 100% of its rated current all the time, which I'm happy to say is not the case. Unlike the AS400, where the PSU is sized specifically for the system, a PC power supply is sized for a specific output. Vendors and assemblers are free to choose whatever PSU they wish. Also, CPUs and GPUs now lower their core voltage and clock speed if the extra performance is not required. The 45W (or 65W, 73W, 90W, 125W) quoted by CPU vendors is the amount of power they are reasonably expected to draw under heavy load, not the idle or average draw. >> My 2 year old desktop uses >> 60-100 watts depending on how hard it's working. >> > Sounds like a notebook / laptop class computer. > I can assure you it is not. I can show the following examples: Core 2 Duo E7400 (about 3GHz), single 7200rpm disk, embedded graphics and network - 44W to 60W depending on what's happening at the time. Adding a discrete GPU (I don't recall the model, but knowing me it's probably a low-end ATI 3000 series) adds 10-30W, again depending on load. Another Core 2 system, an E5200 I think, with 2 x 7200rpm notebook disks, 4GB, embedded graphics and network is also measured at around 45W. I have an overclocked E6300 (running at 2.66GHz, so a 25% overclock), 3GB of RAM, 2 x 7200rpm desktop drives, and a GeForce 7600 that pulls 140W. Note that overclocking generally disables power saving features and increases power use (linear with clock, square with voltage). Servers tend to be worse - I have a matched pair of Acer servers with single 3GHz P4 class Xeons, 2GB of RAM, 3 x 7200rpm disks and dual NICs. Those systems pull 220W and they're the next ones I'm ditching for something that uses less power! All the numbers above are measurements before the PSU input (using the Australian version of the "Kill-A-Watt") so include the losses due to the PSU itself. To go back to Gary's question, however, I would suggest that the new Core i3 series of processors, along with a new board, will use substantially less power than is marked on the PSU, especially if he is not continually encoding video, rendering animation or designing the next Sydney Harbour Bridge (replace with your own national monument if desired). I use this in my HTPC, and it's quite capable of supporting two XBox media extenders and encoding 576p video in close enough to real time, all simultaneously; while doing so it's probably using less than 110W of electricity. Dave. -- David Rawling Principal Consultant PD Consulting And Security Mob: +61 412 135 513 Email: djr@pdconsec.net
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