Path: utzoo!attcan!uunet!wuarchive!zaphod.mps.ohio-state.edu!mips!sjsca4!poffen From: poffen@sj.ate.slb.com (Russell Poffenberger) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: Leave the PC on vs. Power it off daily? Message-ID: <1990Sep27.190011.12366@sj.ate.slb.com> Date: 27 Sep 90 19:00:11 GMT References: <8axQEga00VY642bGAb@andrew.cmu.edu> Reply-To: poffen@sj.ate.slb.com (Russell Poffenberger) Organization: Schlumberger Technologies, San Jose, CA. Lines: 33 In article <8axQEga00VY642bGAb@andrew.cmu.edu> jc58+@andrew.cmu.edu (Johnny J. Chin) writes: >Power On and Off a PC puts the most wear on your hard drives. The spin down >and spin up of the platters causes the spindle to wear out. Leaving the >system on all the time allows the spindle to spin with less friction, thus >less wear. > >As for the components of the computer (ie. the silicon chips), the power spikes >induced by a power on decrease its life (this is more so with the denser VLSI >chips because of the narrower width of the electrical lines). > The problem is more due to thermal expansion/contraction as the chips heat up and cool of with power on/off. A good power supply "glitches" very little. >The problem with leaving PCs on is the load that is induced on the transformers >out in the street. PCs use a switching power supply; what this means is that >the power supply switches "on and off" 60 cycles per second. This does NOT >mean that the PC turns on and off 60 times every second. Because of this >"on and off" of the switching power supply, a larger load is demanded from >the transformers (due to lots of small sudden demands for power). This is simply not correct. First of all, the "switching" section of the supply is powered by DC, after the AC line as been rectified and filtered. The filtering (using large capacitors) masks any load changes caused by the switching action of the supply. Second, switching supplies switch MUCH faster than 60Hz, more along the line of 50Khz and up. Generally, the higher the frequency, the smaller the power supply (to a point) because the inductors used are smaller. Russ Poffenberger DOMAIN: poffen@sj.ate.slb.com Schlumberger Technologies UUCP: {uunet,decwrl,amdahl}!sjsca4!poffen 1601 Technology Drive CIS: 72401,276 San Jose, Ca. 95110 (408)437-5254