---------- Original message ---------- Subject: Re: G4 Cube: possible processors? Date: Saturday, 11. June 2011 From: Doug McNutt <[email protected]> To: [email protected] > At 19:22 -0700 6/10/11, [email protected] wrote: > A batch of good stuff about power usage and clock speeds which I snipped.
Thanks for sharing your knowledge! > Microprocessors built with complimentary symmetry metal oxide transistors, > CMOS, dissipate power only as the states of the CMOS gates are changed. > While sitting in a 1 or 0 state they don't require any power at all. > > So the usage of a chip is proportional to the count of gate changes per > second and not only to the clock speed. In an idle state there might not be > very many gates changing state at each clock pulse. (For completeness, the > power is also proportional to the square of the power voltage.) The power saving features on a G4 processor are very limited compared to those found on a modern multi-core processor. AFAIK a 450 MHz G4 7400 in a Cube always runs at this frequency and sleep/power states aren't as fine grained as modern ACPI C-states and P-states. (P-states is better known as DFS, dynamic frequency scaling.) The first G4's I've heard of to support DFS are the third-party upgrade processor cards with Freescale 7447A processors, but they require additional system software for DFS to work, and not all OS versions (particularly Mac OS X >10.4.9) actually support this (or rather allow for it to work). According to this discussion (which /may/ be wrong alltogether): http://forums.macnn.com/65/mac-pro-and-power-mac/53325/differences-between-g4- g4e-7400-7410-a/ a 7400/7410 has a 4 stage pipeline, and the 7440/7450 a 7 stage pipeline. Are these “stage pipelines” the stage gates you are talking about? > Scientific calculations, games, video which has to be decompressed in real > time, things like that require a lot of calculation and thus a lot of gate > changes at any clock speed. Editing a document while being limited by your > finger speed on a keyboard will not use many gate changes and the computer > power will be lower. > > For a thermally limited cube you could measure the temperature and adjust > the clock speed accordingly. If you try to play some war game that demands > three dimensional viewing depending on your place in the synthetic > environment your machine will slow down. Sorry. You can read your email at > full speed. “depending on your place in the synthetic environment” ??? I'm sorry, I'm not a native speaker. I don't understand. What I did understand, was: The thermal limit depends on where I (the player) has positioned its character (the "hero" of the game) in the virtual world of the game. This cannot be right, right? Anyway, if I got this right, a Dual-533 from a DA (with an adjucted multiplicator to result in being a Dual-500/550/600 MHz) will NOT overheat the Cube, even as a dual processor system. http://www.cubeowner.com/forums/index.php?showtopic=10902 What I didn't find yet is what installation modifications are necessary to get a Dual-533 from a DA (which has a mirrored processor module layout to the GE Dual-450/500) set up in a Cube. > There is a lot of data on the world wide web about overclocking of chips. > The idea originally was to monitor a chip for errors and speed up the clock > until they begin to show up. The acronym was the TEA technique and I have > forgotten the words it stands for. What you're talking about is > underclocking but it's the same idea. Modern chips actually have > temperature sensors on them; they can be read out and perhaps used as in > input to a variable frequency clock. > > A maximum speed clock connected to a programmable downcounter chip would be > pretty easy to set up, trivial if you could use a simple interface to code > running on the processor itself but more difficult if Apple limits you to > the likes of USB or Ethernet. There are also analog schemes for making a > variable frequency oscillator that could be controlled by a thermistor on > the heat sink. They would be slower to respond. This is too much of modding for me, but would certainly be a very brave task to do… Thanks! Andreas aka Mac User #330250 -- You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list
