Burning Hot

Scott Billings wrote:
Not sure where it is people get these crazy tinfoil hat style conspiracy theories.

Whoa, easy does it, Scott. As far as I can tell, nobody’s claiming any conspiracies here. You’ve taken a few simple suggestions for helping to keep our Macs running a bit cooler and extrapolated somewhere out into the ether. Perhaps a few deep breaths might be in order.

Those programs create a number of problems down the road.

I've heard you say that before. Solid evidence for that? Statistics?

They can create false-positives with diagnostic programs for one, and they can prevent the fans from spinning faster if needed.

Easy enough to disable them before doing diagnosis.

Apple may let things run a little hot, but there's no way they'll let them get to a point where it may damage components. They're on the hook for repairing the things for at least the first year... Everything they do is aimed at maximizing the amount of money they make. You don't accomplish that goal by taking actions that will cost you money in the end.

Heat related problems from slow baking of components may show up three, four years down the road (many don't take AppleCare, and I wouldn't be surprised if that's figured in to the equation), while these kinds of problems are unlikely to show up in the first year. I'm not talking about temperatures approaching a thermal shutdown, just garden variety hot running which these components can easily tolerate for a single year before croaking. (My opinion is based on the extensive experience of a highly skilled Apple bench tech.)

If we're going to focus on the profit motive, one could easily make the far more convincing argument that Apple ends up selling more computers for the reputation of quiet fans and, on balance, makes more money, regardless of the consequences down the road three to four or more years out.

And, finally, can we allow others to have a difference of opinion on these matters? Can you stop shouting, please.

dbax wrote:
With all due respect to rkaufmann and Scott,Billings you are right to be concerned about the temperature of your Mac. Heat is the enemy of electronic components and excess heat will shorten their life.

There is quite a bit more to it than that. Different components have different tolerances for heat; in fact, some work better when relatively hot than cold. Unless you have engineering or design experience, it is probably best to leave this to those that do. For instance, the Intel Core i5/i3 Thermal Design Guide is over 100 pages long, & a substantial amount of it is dedicated to fan speed control guidelines for optimally cooling the CPU in integrated, multi-sensor systems like the iMac uses. As you might imagine from its length, trying to reduce this to "cooler is better" is a vast over-simplification of what is actually a design process carefully optimized for the best overall performance, including longevity of the entire system.

What may not be so obvious is that this requires a system wide approach. For example, in a three fan system +all three+ fans contribute to how cooling air flows through the case, cooling everything in it to one extent or another. Changing the speed vs. temperature characteristics of one fan will change how everything is cooled, including when & how much the other fans speed up. It might be counter-intuitive, but speeding up a fan can actually cause some parts to overheat.

How can this be so? Consider that the cooling system in a Mac is nothing like an air conditioner with a thermostat on the wall. A Mac uses a small, built-in computer (the SMC) to adjust fan speeds based not only on temperature sensors but also ones that monitor power consumption, & how these values change over time. Implicit in the programming of the SMC are assumptions about the layout of the parts & how air flows over them in response to fan speed changes. Speeding up one fan may cause more air to flow across parts that don't need more cooling & less across others that do. If the parts don't have their own sensor (& most do not, even in the most recent designs) the SMC will never know what's going on.

Moreover, temperature sensors themselves may be affected, for instance by being near an area of localized increased cooling air volume & thus not accurately reporting the temperature of the item they monitor. (If you wade through engineering design guides you will notice great care is required in the placement of test sensors, in part because of this effect.)

There are other factors to consider as well, like thermal stresses caused by uneven heating & cooling, & the rate of dust ingestion, but the bottom line is the cooling system is a tightly integrated, very carefully designed one, created by some of the best qualified & most experienced electronics engineers in the business. The chances that they have overlooked something that users have "discovered" on their own are close to zero, while the chances that users have overlooked something they have not is much, much higher.

RC-R wrote: How can this be so? Consider that the cooling system in a Mac is nothing like an air conditioner with a thermostat on the wall. A Mac uses a small, built-in computer (the SMC) to adjust fan speeds based not only on temperature sensors but also ones that monitor power consumption, & how these values change over time. Implicit in the programming of the SMC are assumptions about the layout of the parts & how air flows over them in response to fan speed changes. Speeding up one fan may cause more air to flow across parts that don't need more cooling & less across others that do. If the parts don't have their own sensor (& most do not, even in the most recent designs) the SMC will never know what's going on.

This all sounds good, but bottom line, I would just want to ask, and this from my own experience, as well as that of others, why it is that the fans do not seem to speed up except in the case of the most exceptional kinds of temperatures? For example, I'm talking about letting HD temps reach 50-60C for prolonged periods without any fan speedup.

Message was edited by: WZZZ

Not sure where it is people get these crazy tinfoil hat style conspiracy theories.

They aren't crazy tinfoil hat conspiracy theories. They are logical, rational deductions. Unfortunately, they are usually based on a very limited understanding of the interrelated complexities of electronics design, failure mechanisms, & so on.

Techs are not immune to this either. Many years ago, I owned & operated an electronics repair business. Some of my best techs mis-attributed failures to design flaws that further investigation clearly showed to be well within -- & often below -- the normal, expected failure rate for the type of equipment they worked on. No craziness was required to explain this: if 90% of what you see is failed equipment, it is very easy to succumb to the idea that it is a representative sample of all of that model or product type, when in reality there is an inherent sampling bias that must be eliminated before any justifiable conclusions can be reached.

Simply put, being a skilled repair tech does not make anybody a design expert. It can give one insights regular users may lack, but it also can create its own blind spots.

Brad87:

I would not add any program that can be used to alter the fan RPMs. The default settings should be sufficient. If not, then there is something wrong. If it's too hot for your hands, then it's too hot to function. Cut out all of this discussion and take it to Apple. I have an all aluminum casing and it does get pretty warm sometimes but not enough to burn my hands and not enough to worry about. If you don't have it reported and checked, you will not sleep at night and if your fears are justified, you will shorten the life of your computer and hopefully it will fail before the three year period is up assuming you have the extended warranty. If you don't do anything about it, I would strongly suggest you get the extended warranty if you don't already have it.

{quote:title=R C-R wrote:}
They aren't crazy tinfoil hat conspiracy theories. They are logical, rational deductions. Unfortunately, they are usually based on a very limited understanding of the interrelated complexities of electronics design, failure mechanisms, & so on.

In plenty of cases, they are tinfoil hat brigade material, and then some. You're making a very common, and very normal, attempt to attribute some kind of logical thought process where there isn't necessarily one.

Sometimes, yes, people just don't really have all the facts... But there are plenty of people, and I'm sure you saw this when you ran that business, who are absolutely convinced that there is some kind of a conspiracy against them. Maybe not them specifically, but how companies are out to rip them off. How a company designs some product to break just outside of the warranty period or whatever other crazy nonsense they can come up with.

When I used the term tinfoil hat brigade, it's meant along the same lines of me calling people like myself repair monkeys. I can't very well call the people who work in Apple stores repair monkeys without including myself, because I do the exact same thing, just not at an Apple store. Doesn't bother me, and I see absolutely nothing offensive about the term. If anything, it's marginally affectionate in a playful sort of way.

Techs are not immune to this either. Many years ago, I owned & operated an electronics repair business. Some of my best techs mis-attributed failures to design flaws that further investigation clearly showed to be well within -- & often below -- the normal, expected failure rate for the type of equipment they worked on. No craziness was required to explain this: if 90% of what you see is failed equipment, it is very easy to succumb to the idea that it is a representative sample of all of that model or product type, when in reality there is an inherent sampling bias that must be eliminated before any justifiable conclusions can be reached.

A fair point, and so I'll ignore the breaking of the cardinal "Thou Shalt Not Quote Wikipedia and Expect To Be Taken Seriously" rule.

I actually make a point of trying to avoid that very problem. I may not always succeed, but I try.

Of course at the same time, just because something may be well within spec doesn't automatically make it a good spec to begin with. I'll point to USB as an example. I don't think anyone would really want to take credit for that design as a matter of pride.

Simply put, being a skilled repair tech does not make anybody a design expert. It can give one insights regular users may lack, but it also can create its own blind spots.

It may not make you an expert in the sense most people think of an expert... But you start learning about things, and sometimes you can see how this or that could have been done better. Now maybe there were other considerations you're not aware of as to why it is the way it is, and I'll readily admit to that possibility. But sometimes there is no good reason why something was done a particular way. It's just a plain and simple bad design.

That's great, although I have no idea what was causing the sleep issue I'm pleased it has been resolved. I'm sure you will be keeping an eye on the heat and I hope you have many years of enjoyment from your iMac.

Regards,

Roger

What are you basing those HD temperatures on? Do you know exactly where the temperature sensor is located, how well it is calibrated, & how well it represents temperatures in the most heat-sensitive parts of the HD?

People often get the idea that both spec sheets & sensor read outs say more than they do. For instance, a HD bay sensor may or may not be located at the same place a manufacturer's spec sheet specifies for HD case temperature measurements. That or a specific heat sink design may change the correlation between sensor & HD temperature, even for embedded temperature sensors.

In terms of temperature measurement a HD is not a single thing but many of them.

All of that would seem to beg the question. All of this monitoring is done with Apple engineered, calibrated and installed devices/sensors which, unless I'm mistaken, are feeding the same data to the system fan program as goes to some third party temperature app such as the highly regarded and accurate Hardware Monitor, or Temperature Monitor (which I know to be calibrated, unlike some, to interpret raw values.)

It isn't just a temperature monitoring program with a proportional fan control output. It is a tightly integrated, highly complex system that communicates with many devices to negotiate the best tradeoff among factors including power consumption, temperature rise & duration, operating environment, & everything else that has to do with performance.

If you just look at the temperature data (which the SMC provides to the third party apps anyway) you can't begin to see the whole picture. Older SMC's have over 200 registers, the latest ones around twice that. They have I2C busses, dedicated 'dumb' sensor inputs & control outputs, & many possible operating modes.

The only question that matters is what the effects are of more or less blindly tweaking fan set-points. The answer to that is much more complicated than is generally understood.