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What Makes Apple's Power Mac G5 Processor So Hot
An anonymous reader writes "58 million transistors can drive a lot of power. Apparently, Apple appreciated the choices IBM processor architects made when designing the 970 family. This article provides the 64-bit architecture big picture for the 970 family (A.K.A. the Power Mac G5) and the critical issues in IBM's 64-bit POWER designs, covering 32-bit compatibility, power management, and processor bus design."
If it's so hot, maybe it's not cool enough.
Insufficient cooling?
Basically, we took one of our superchips that go into superservers, with a gitastic cache and frontside bus, stripped it down a bit so we don't cut into our own market, and gave it a new name. Isn't that cool?
The difference between spam and poop is that you don't have to dig through septic tanks looking for real food. -- Me
"Backups are for wimps. Real men upload their data to an FTP site and have everyone else mirror it." -- Linus Torvalds
I was able to hold my hand on the heatsink and it was barely warm.
It could be because there's inadequate conduction between the CPU core and the heatsink. Check the temperature monitors to make sure it's actually as cool as you hope it to be. It could be that just most of the heat is staying in on the CPU, which would be a bad thing. Hopefully you've already checked this though.
-GillBates0, 2004.
An Indian-American Hindu committed to non-violent thought/speech/action alarmed by the global explosion of radical Islam
The fan belt on its search engine doesn't drive the radiation air emission unit fast enough! SHE NEEDS MORE POWER!
They should make the G5 powerbooks have a teflon underside.
"Turn it over, and you can cook dinner".
One side-effect of 64-bit computing that I don't hear a lot of discussion about is the increase in the size of a pointer. A standard implementation of a linked list of integers will now be 50 to 100% larger (depending on if you use 32 or 64 bit integers), simply because the pointers take up more space. If I bought a 64 bit system, simply because it's the "Best", but only got 1GB of RAM, I have less useful memory, because the pointers take up all of my physical RAM. Do the architects of these systems take this into account?
Sometimes I doubt your committment to SparkleMotion!
I'll probably get modded down for saying this, but I have Karma to burn...
That article is some crybaby whining about how expensive the G5s are. "Apple is so dumb. Why would anyone pay that much for a CRAP computer," is what the article sounds like. I think that guy needs to take his superior knowledge elsewhere and try some benchmarks ("512K of cache isn't competitive for $3000")... apparently it is because it's winning benchmarks and people are buying them. Just because you can't afford it doesn't mean it's a bad computer (doesn't mean it's a good computer either). This guy needs to grow up and write an article with facts instead of emotions...
My other car is first.
I recently upgraded to a 754-pin Athlon64 3000+, and the hottest it's ever been is 51 C, a few degrees more than the room temperature of 43C. On a cooler night, with 100% CPU load for ~2.5 hours [2-pass XviD encoding], it peaked at 47 C. Quite impressive.
Use ISO 8601 dates [YYYY-MM-DD]
Most importantly, it can address up 2^64 bytes of memory. And yes, that generally implies 64-bit integer GPRS. BTW, vector operations on x86 (MMX) also operate with 64 bit registers, but it can only access 4G (32G if you use the extended bits "hack").
The Raven
Does anyone have the numbers to compare how many watts of power the G5 uses vs a similar AthlonXP or AMD64? Ie, I'd like to see how a 2.0 or 2.5 GHz G5 compares to a 2.0 or 2.5 GHz AMD processor.
Capable of addressing an astronomical 18 billion GB, or 18 exabytes, of memory,
I know the first 2 digits are 1 and 8, but 2^64 bytes is still 'only' 16 exabytes...
Obligatory PC Weenies link that fits the topic at hand.
The PC Weenies: 11 Years of Online Tech 'Too
umm, what heat problem? the 9 fans and liquid cooling are in their respective models to solve a SOUND problem. not a heat problem. but then if you bothered looking up statistics on the G5 you would not be able to bash the mac would you?
I am the Alpha and the Omega-3
The notable exception is the Arm's thumb instruction set (it's cool).
The sad part "my address bus is bigger than you" is going the "I have more MHz than you" way soon as parallel CPUs (mulit-core or otherwise) become cheaper.. 90% of our tasks are better done parallel than using a single fast chip . Hell , half of the tasks really don't need anything beyond a 300/400 mhz clocks.Quidquid latine dictum sit, altum videtur
The power coming out of a chip is marginal; it's pretty much all converted to heat.
In the past few years where PC' Fanatics have gone to great measures in extreme clocking and tweaking to push the speeds to the limits, Mod'rs have ran into and pretty much conquered heat issues along with other roadblocks. Technology that has been adapted by PC and PC-part manufacturers, I'm no Mac expert but even thumbing through the latest magazines I have yet to stumble upon a "Mac" mod or a how-to on making them extreme, is this due to proprietary or licensing issues? Or can a Mac be reverse engineered the way PC's can be? Granted Macs are not worthless and have good reviews from most of its users that know the systems. Still I find it limiting and where PC has prevailed. Heat on a slower clock speed processor should not be an issue. How many fans does a G3, G4, G5 have these days (1 case)? Laptops would be even worse as for PC portables are highly concerned about heat themselves.
"Make it idiot proof, Someone will make a better idiot" -- Tweak
Coob
Your iMac G5 has two fans. Not much space left for additional cooling, really, without interfering with the current cooling setup.
Your PowerMac G5 has nine fans. Again, not much space left for additional cooling without interfering.
And get this, the PowerMac G5 already uses a liquid cooling setup. The only possible additional mod is to hook the current setup to a resevoir and radiator on the outside of the case, as the inside already has a radiator per CPU and something like a 120mm fan per CPU.
GPL Deconstructed
The *BIG* thing for x86 for "64bit computing" is not in fact the 64 bitness but doubling the number of GPR!
As the PPC instruction set is sane (x86 is not, urgh), beside the extra-instruction needed for 64 bit computing, there are very few difference between a PPC running on 64bit code or a PPC running on 32bit unless of course you have an app which needs more than 4GB of memory or do lots of 64-bit integer calculation..
It's not a matter of total heat dissapation as much as the fact that the head is dissapated in very small areas of an allready tiny chip.
The PPC970FX actually doesn't produce that much heat compared to the current AMD and Intel crop, only dissapating 54W typical at 2.5Ghz (albiet a good deal higher at peak). But due to it's smaller die, it has to dissapate that heat from a smaller area, thus requiring a cooler heat sink to dissapate it into to maintain the same die temperature.
It's basic thermodynamics, but something geeks often overlook.
I can buy .8-1.2ghz processors and motherboards that use extremely little power (tens of watts running full bore) and are certianly very useable with even windows XP running on it as a internet/ general use home or office pc.
But for some reason most people believe they need a 6.8ghz 2.2terabytes of ram and 15,000 rpm hard drives along with a hairdryer add on known as a 3d video card, bringing that machine up to the 400 watts+ power consumption mark.
and where does most of that energy go?? that 's right . HEAT.
Switch to mini-itx computer with a low-power processor, laptop hard drive and flat panel monitor, and you will generate very little heat, use 1/20th the electricity your current space heater under your desk called a comouter does and still get the same general computing done with the same speedy feel.
will you increase your lead in the seti@home, doom3, other CPU intensive tasks? nope. but office 2003, WinXP and all other office apps as well as most non 3d intensive games run perfecly.
Do not look at laser with remaining good eye.
The G5 2.5 dualie I just received puts out waaaaay more heat than any computer I've ever seen. I had to move it out from under my desk to the side to allow the heat to escape. It was much more than a foot warmer.
cat
It used to be that Mac fanatics would be proud about how little current the PPC used -- and consequently how little heat it gave off -- when compared with the Intel-style architecture. Guess we can't make that argument any more.
Now that G5's are liquid cooled, it makes me wonder if a 2.5GHz G5 is *really* a 2.5GHz G5, or if it's an overclocked 1.8GHz chip. You know, overclockers really pump things up with cool liquid cooling stuff. What's the fastest a 2.5GHz G5 could run with a traditional cooling system, like a fan and heatsink?
Oh, one more thing before I'm modded as a troll: my G4 PowerBook is my 8th Macintosh. What I'm asking is genuine curiosity.
--Jim (me)
Introduction to 64-bit computing
/wishes he had exa-bytes of memory right now... VS.NET on WinXP is a PIG!
There's an informative link at the bottom of the article for those requiring a bit more insight into the effect of 64-bit computing.
-- All views expressed in this post are mine and do not
-- reflect those of my employer or their clients
is there another reason to use liquid cooling, other than excessive temperature?
Not sure if this is the reason, but its not just a matter of amount of heat generated. Its the amount of heat generated in a given area. So if you generate the same, or even less, heat in a smaller area, you may need to resort to something more efficient that air cooling to do the job.
Just because you can't afford it doesn't mean it's a bad computer (doesn't mean it's a good computer either).
Hear hear.
I've priced out equivalent machines to the current Apple offerings, and you do indeed get what you pay for. A dual-CPU 1.8Ghz Powermac is around $2500 sans monitor. Price out a dual-Xeon or dual-Opteron and you end up at around $2000-$2500 for a comparable system.
Where Apple might be missing the boat is in the ultra low end where you can buy a system for $600. (But why should they try to compete down there where margins are razor-thin?)
Wolde you bothe eate your cake, and have your cake?
The quest for CPU power has been largely defeated by bloated software in applications and operating systems. Some programs I wrote in Basic on an Apple II ran faster than when written in a modern language on a G4 Dual-processor Mac with hardware 1,000 times faster.
Come on. What language are we talking about here? My basement collection includes a II+, a IIe, two IIcs and a Franklin compatible. I challenge anyone to come up with a program in Applesoft that runs faster on one of my museum pieces than on a modern Mac using C++, Java or even Perl. I mod his article -1 for troll.
While software has become bloated and to some extent inefficient, people often forget that we expect a lot more from our computers now than the single-tasking 80 column display days.
My cat can eat a whole watermelon
I agree, big time.
I used to be very pleased that my Macs lacked a CPU fan while x86 users where bolting on everything but the kitchen sink in efforts to cool their systems down.
More important, Macs had just one fan -- the power supply fan -- to cool the entire box while x86 systems were fucking festooned with them.
Nowadays, though, a prudent Mac owner should at least consider his home air-conditioning system's cooling capacity since G4's and G5's will definitely heat up a room.
And I don't even want to get into fan counts.
I'd like Apple to make a nice, fast, cool, quiet system... and here's how to do it: underclock.
Modern CPU's are grotesquely overpowered for the needs of 99.9% of the general public. Crank those babies back.
The fruit of research and progress are not merely systems that can run faster and hotter, but faster and cooler... quieter.
Never going happen while there's this pissing contest going on, though.
--Richard
Simple. Since we've got a computer capable of simulating the entire universe, we'll just use it to simulate a universe which contains a computer which is capable of simulating more than one universe.
If you don't need that kind of power, you should stay on the lower end. The G5 iMac or the eMac don't seem to run all that hot.
As for fan count, presumably you're referring to the PowerMac G5. Apple preferred more low-speed fans over a few high-speed fans as a noise reduction measure. What was your complaint?
Where Apple might be missing the boat is in the ultra low end where you can buy a system for $600. (But why should they try to compete down there where margins are razor-thin?)
Because poor college students like me, who buy $600 computers is going to buy a PC. And when I get out of college and have the means to drop $2500 on a computer, guess what I'll probably buy.
Actually, the two real reasons why Apple doesn't sell low end machines is that it would undercut sales of their more expensive machines, and totally destroy the second hand Mac market (where used Macs are way overvalued, IMHO). Without a strong second hand market to sell a used Mac for a good price, people will be less likely to buy their high end machines.
for literal heat, this puppy is pretty hot.
my dual 2.5GHz PowerMac G5 idles at 52C (125F) on CPU A and 50C (122F) on CPU B. the memory controller is actually one of the hotter things, it idles at 62C (143F). however, it's not the hottest thing, of course: at full load (DVD rip+encode or playing 15 videos at once + MP3 + tasks + flicking around Exposé) both CPUs have hit a max of 83C (181F) (the computer is supposed to automatically sleep around 90C or so).
so why so effing hot? i mean, this idles at the max temp my athlon 2500 peaks at! it certainly idles at a hotter temp than it needs to, but i have no problem with that: the system runs the fans dynamically to keep the noise down, so at idle it's not as cool as it could be. the difference in noise in my room when i sleep the athlon is ridiculous - the G5 sounds like a slightly loud external hard drive that's spun up. the system also has a liquid cooling system to quench the processors. this seems to just keep the processors within their range. the value that i see in it is response to new heat - the CPU temps flick around a lot and are very responsive to load and the loss of load. after ramping up the CPUs to >80C, it take about three or four seconds after the load drops for the CPU temps to drop 15-20C, then maybe a total of ten or twelve seconds to drop to idle temp.
for some real-world perspective... a DVD rip+encode with HandBrake with using ffmpeg engine, MP3 audio, 2-pass encoding, and gunning for your average 700MB movie time (800-1300kbps?) takes slightly less than the length of the DVD. an hour and a half long movie took about and hour and fifteen minutes to get on to my hard drive. MP3 ripping in iTunes will run up to 28x, but it's not fully loading the processors so i wonder about a drive read bottleneck. the first night i got it, i was at a loss for how to really test the speed on it, so i just decided to open up a shitload of videos. basically i played a DVD (fluff, the GPU does that), opened up something in VLC, opened up about 13 videos in QuickTime of various sizes and formats, played some MP3 music (fluff again, that's ball sweat of a cutting edge proc), and still had enough processing power to comfortably navigate files, chat, browse web pages, and flick around Exposé. around all of these things plus one is when a few of the videos would start stuttering and expose would start dropping frames to keep collapse speed uniform. anything past this would really start robbing time from videos.
all in all? it's fast. it's quiet. it gets hot, but it takes care of itself. coming from a 375MHz G3-upgraded PowerMac 7600 (vintage '98), i'm not doing too shabby. i just decided i'd scramjet at mach 7 to the top of the pack and then sit there for another few years.
- emilio
neurostyle dot net - it's all in your head
What if our universe is only a simulation running on a computer in another universe?
Maybe it's possible to disprove this based on the idea that the other universe would need to be physically larger?
My other first post is car post.
That would go a long way to explain the "disappearing sock" phemonenon...
They use liquid cooling because it's harder to disapate the heat from the small 90nm core. The CPU's don't use much power, it's just that the heat they do produce is concentrated in such a small area. Better cooling is required to disapate this heat.
90nm transiters require less power then their larger counterparts. The problem is, for the same die size they use more power. So you end up with a relatively low power CPU that requires massive cooling.
Apple and IBM had a lot of problems because they expected their new CPUs that consume less power to be easy to cool. They were wrong. For each square mm, more heat must be disapated.
But that's why people buy macs. To use photoshop quickly. So how long a filter application takes is very relevant.
:)
I don't have a mac here, but opterons and g5s are probably similar. Pick the one you like, they're both expensive
My other car is first.