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Maximum room temperature
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. |
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Maximum room temperature
baggins2000 wrote:
What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. According to this, the max temp for the 125W 9950 is 61C. I'd like to dig up more info for you (like verifying in a processor spec document, that what is printed here is accurate), but the AMD web site doesn't make that easy. I'm not even sure there is a separate thermal spec as such. http://products.amd.com/en-us/Deskto...il.aspx?id=447 Two aspects of cooling are important in a computer. There is the ability of the rear exhaust fan, to pull hot air out of the computer case. That is important, because otherwise heat would build up inside the case. If you sealed the computer case, the stuff inside would be boiled alive. The CPU fan moves heat from the CPU heatsink, into the internal computer case air. The CPU cooler cannot do its job, without a well cooled case. If your motherboard has a "case temperature" sensor, then you can get some idea of how well it is cooled. For example, let's do some arithmetic. Say the room temperature is currently 25C. One article I read, declared that a well cooled computer case (one with adequate rear exhaust fan), would allow the internal case temperature to reach 7C higher, or 32C. That requires a relatively good airflow (fan won't be silent). Using those assumptions, we can work out the requirements of the CPU heatsink. If 61C is the CPU max case temp, and 32C is the internal air temp, the difference is 61C - 32C. We assume the CPU is running at 100%, with all cores running at max. Say, a copy of the latest Prime95 executable with multithreading is running. The above product listing says the TDP of the processor is 125W. That is purely an estimate, and the real power can be exactly equal to that, or a value which is quite different. (For example, my current 65W TDP CPU, never draws more than 36W, meaning it runs a lot cooler than the spec says. Still, we have to make some assumption, to do the arithmetic.) The ratio of delta_T to power in watts, is called Theta_R or the thermal resistance. We can work out the heatsink required now. 61C - 32C Theta_R = ---------- = 0.23 C/W 125W Now, we compare that to a Zalman CNPS9700. If the fan runs at full speed on that particular CPU cooler, Theta_R is 0.12 C/W. That means, in the above arithmetic, we meet the requirements. I found that number on this site - the number is no longer listed on the Zalman site. And many companies don't want to give this number, because it makes cooling design too easy. http://www.crazypc.com/products/50992.html We can also work out, what the maximum internal case temperature can be, using our new CNPS9700 heatsink. 61C - X 0.12C/W = ---------- , 61C - (0.12C/W * 125W) = X = 46C 125W Since we've defined the case to be 7C hotter than the room, and X is 46C, we know the room is 39C. Therefore, if we use the fancy Zalman 9700 family cooler (like the 9700NT with four pin fan connector), we can allow the room temperature to hit 39C, and at that point the CPU will be at 61C. But, remembering as well, that there must be sufficient airflow through the case, such that the internal case air is only 7C warmer than the room. By now, you might be saying, "how can I figure out what fan to use for the case ?". Well, there is an equation for that too. Now, for this one, you need to know all the thermal loads inside the computer case. We have the 125W processor, say a 100W video card, two 12W hard drives, say a total of 250W. Our definition of a well cooled case, is 7C, which is equal to 12.6 Fahrenheit degrees. Plugging in the values. CFM = 3.16 * Watts / Delta_T_degrees_F CFM = 3.16 * 250W / 12.6F = 62.7 cubic feet per minute. Now we go shopping. The Newegg fan page, Advanced search option, has the ability to select a range of CFM. I picked this cheap fan from the search result. http://www.newegg.com/Product/Produc...82E16811998124 Fan Size 120mm RPM 1700rpm Air Flow 63.85CMF Noise Level 29.67dBA This fan meets our cubic feet per minute requirement. It allows the room to reach 39C while the processor runs flat out. However, the noise level is about 30dBA, which is a rough number for "man, this fan is annoying". Now, if we use a fan controller knob, to slow the fan down, and say run it at 70% of full speed, the computer case air gets warmer. Say it gets warmer by 3C, then we'd have to drop out maximum room temperature by 3C as a result. So you can trade noise, for max room temperature. With a slightly quieter fan (or a noisy fan with voltage reduction), we might take a room temp of 36C. Now, when my room hits that temp, I'm usually not interested in sitting in front of the computer, and I head out on the patio. You'd have to be paying me, to sweat in that. Another question would be, how hot is the hard drive. I cannot answer that one. I personally treat hard drives better than I treat CPUs, and would be monitoring the hard drive more closely than the CPU. The CPU has its own protection mechanisms - if the heatsink on the CPU falls off, the CPU will actually shut off the ATX power supply without warning (so there is no opportunity to save your work - the power just goes off). So the CPU will protect itself, if something nasty happens. The same cannot be said for the hard drive, which cannot defend itself. Note that the above "29.67dBA" noise figure is pure fantasy. No two people measure noise the same way, so you cannot compare the numbers you find in catalog listings. Instead, read the customer reviews and "average" out what they say about noise. That is a better indicator than the 29.67 number. Still, as mentioned previously, if you cannot get customer reviews, sometimes you're forced to rely on that 29.67dBA number. Having written all that, perhaps now you can explain to me, what you plan to do. Are you going to put the computer in a crawl space or a closet ? Well, don't do that. Computers need to breathe, to stay cool. HTH, Paul |
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Maximum room temperature
Paul wrote: baggins2000 wrote: What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. According to this, the max temp for the 125W 9950 is 61C. I'd like to dig up more info for you (like verifying in a processor spec document, that what is printed here is accurate), but the AMD web site doesn't make that easy. I'm not even sure there is a separate thermal spec as such. http://products.amd.com/en-us/Deskto...il.aspx?id=447 Two aspects of cooling are important in a computer. There is the ability of the rear exhaust fan, to pull hot air out of the computer case. That is important, because otherwise heat would build up inside the case. If you sealed the computer case, the stuff inside would be boiled alive. The CPU fan moves heat from the CPU heatsink, into the internal computer case air. The CPU cooler cannot do its job, without a well cooled case. If your motherboard has a "case temperature" sensor, then you can get some idea of how well it is cooled. For example, let's do some arithmetic. Say the room temperature is currently 25C. One article I read, declared that a well cooled computer case (one with adequate rear exhaust fan), would allow the internal case temperature to reach 7C higher, or 32C. That requires a relatively good airflow (fan won't be silent). Using those assumptions, we can work out the requirements of the CPU heatsink. If 61C is the CPU max case temp, and 32C is the internal air temp, the difference is 61C - 32C. We assume the CPU is running at 100%, with all cores running at max. Say, a copy of the latest Prime95 executable with multithreading is running. The above product listing says the TDP of the processor is 125W. That is purely an estimate, and the real power can be exactly equal to that, or a value which is quite different. (For example, my current 65W TDP CPU, never draws more than 36W, meaning it runs a lot cooler than the spec says. Still, we have to make some assumption, to do the arithmetic.) The ratio of delta_T to power in watts, is called Theta_R or the thermal resistance. We can work out the heatsink required now. 61C - 32C Theta_R = ---------- = 0.23 C/W 125W Now, we compare that to a Zalman CNPS9700. If the fan runs at full speed on that particular CPU cooler, Theta_R is 0.12 C/W. That means, in the above arithmetic, we meet the requirements. I found that number on this site - the number is no longer listed on the Zalman site. And many companies don't want to give this number, because it makes cooling design too easy. http://www.crazypc.com/products/50992.html We can also work out, what the maximum internal case temperature can be, using our new CNPS9700 heatsink. 61C - X 0.12C/W = ---------- , 61C - (0.12C/W * 125W) = X = 46C 125W Since we've defined the case to be 7C hotter than the room, and X is 46C, we know the room is 39C. Therefore, if we use the fancy Zalman 9700 family cooler (like the 9700NT with four pin fan connector), we can allow the room temperature to hit 39C, and at that point the CPU will be at 61C. But, remembering as well, that there must be sufficient airflow through the case, such that the internal case air is only 7C warmer than the room. By now, you might be saying, "how can I figure out what fan to use for the case ?". Well, there is an equation for that too. Now, for this one, you need to know all the thermal loads inside the computer case. We have the 125W processor, say a 100W video card, two 12W hard drives, say a total of 250W. Our definition of a well cooled case, is 7C, which is equal to 12.6 Fahrenheit degrees. Plugging in the values. CFM = 3.16 * Watts / Delta_T_degrees_F CFM = 3.16 * 250W / 12.6F = 62.7 cubic feet per minute. Now we go shopping. The Newegg fan page, Advanced search option, has the ability to select a range of CFM. I picked this cheap fan from the search result. http://www.newegg.com/Product/Produc...82E16811998124 Fan Size 120mm RPM 1700rpm Air Flow 63.85CMF Noise Level 29.67dBA This fan meets our cubic feet per minute requirement. It allows the room to reach 39C while the processor runs flat out. However, the noise level is about 30dBA, which is a rough number for "man, this fan is annoying". Now, if we use a fan controller knob, to slow the fan down, and say run it at 70% of full speed, the computer case air gets warmer. Say it gets warmer by 3C, then we'd have to drop out maximum room temperature by 3C as a result. So you can trade noise, for max room temperature. With a slightly quieter fan (or a noisy fan with voltage reduction), we might take a room temp of 36C. Now, when my room hits that temp, I'm usually not interested in sitting in front of the computer, and I head out on the patio. You'd have to be paying me, to sweat in that. Another question would be, how hot is the hard drive. I cannot answer that one. I personally treat hard drives better than I treat CPUs, and would be monitoring the hard drive more closely than the CPU. The CPU has its own protection mechanisms - if the heatsink on the CPU falls off, the CPU will actually shut off the ATX power supply without warning (so there is no opportunity to save your work - the power just goes off). So the CPU will protect itself, if something nasty happens. The same cannot be said for the hard drive, which cannot defend itself. Note that the above "29.67dBA" noise figure is pure fantasy. No two people measure noise the same way, so you cannot compare the numbers you find in catalog listings. Instead, read the customer reviews and "average" out what they say about noise. That is a better indicator than the 29.67 number. Still, as mentioned previously, if you cannot get customer reviews, sometimes you're forced to rely on that 29.67dBA number. Having written all that, perhaps now you can explain to me, what you plan to do. Are you going to put the computer in a crawl space or a closet ? Well, don't do that. Computers need to breathe, to stay cool. HTH, Paul Excellent response, Paul. The only thing I would add is that in order to flow the required air volume through the case there must be sufficient intake area to accommodate the exhaust fan. |
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Maximum room temperature
Oldfart wrote:
Excellent response, Paul. The only thing I would add is that in order to flow the required air volume through the case there must be sufficient intake area to accommodate the exhaust fan. That's a good point, and something I had to fix on one of my computer cases. One area I didn't address, is what happens when you use multiple fans. The CFMs don't add together directly. Sometimes, one fan actually ends up working against another fan (I had air blow *backwards* through a hard drive cooler once - pretty funny). So I lack the technical details, of how to deal with the air volume versus resistance curves and the like. The CFM printed on the fan is not the whole story. But at least it gets you into the right ballpark. Paul |
#5
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Maximum room temperature
'baggins2000' wrote:
What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. _____ The short answer - it depends. The maximum room temperature allowable depends on how good your heat sinks and case ventilation are. Very good heat sinks, along with good case ventilation will keep your computer running at a room temperature too high to be healthy for you (say, 50 C or 122 F). On the other hand your particular CPU heatsink/fan combination, other heat sinks, and the volume of air moved through the system case might NOT be good enough. A better heatsink (larger, more fins, more conductive metal, flatter/smoother/more parallel CPU interface, higher air flow, and perhaps internal heat pipes) will have a lower thermal resistance. That improvement gives a greater temperature difference between the air entering the heatsink and the CPU/GPU/chipset/memory. CPUs (Intel in particular) are designed to run properly under very hot conditions because stuff happens - dirt and dust clogging the heatsink fins, poor case ventilation, high room temperatures. Because the manufacturer doesn't want returns. Since the Pentium 90 Intel CPUs have been protected from damage caused by overheating. That is probably now true for recent AMD CPUs. The ability to overclock depends on the individual processor, motherboard, heat sinks, ventilation and power supplies stability. The maximum room temperature for proper overclocked or non-overclocked operation depends on the same things. Phil Weldon "baggins2000" wrote in message ... What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. |
#6
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Maximum room temperature
Thanks, for the info
I'd would have to rate this as the best set of responses in 8yrs. Very informative. Maybe needs another post, but you mentioned Zalman fans. I have one, but I am not that confident that I put in on correctly. Do you have a recommendation on procedures for installing Zalman fans or just about any of these larger fans. I'm always worried I'm going to install this thing a little off of the chip. The first time I tried to install it looked like I had left a 1/4 of an inch off of the chip and the whole chip wasn't covered. And on one fan I'm having a heck of a time checking the position (Zalman CNPS 7700 ALCU). On Feb 19, 6:04*pm, "Phil Weldon" wrote: 'baggins2000' wrote: What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. *I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. _____ The short answer - it depends. The maximum room temperature allowable depends on how good your heat sinks and case ventilation are. Very good heat sinks, along with good case ventilation will keep your computer running at a room temperature too high to be healthy for you (say, 50 C or 122 F). * On the other hand your particular CPU heatsink/fan combination, other heat sinks, and the volume of air moved through the system case might NOT be good enough. *A better heatsink (larger, more fins, more conductive metal, flatter/smoother/more parallel CPU interface, higher air flow, and perhaps internal heat pipes) will have a lower thermal resistance. *That improvement gives a greater temperature difference between the air entering the heatsink and the CPU/GPU/chipset/memory. *CPUs (Intel in particular) are designed to run properly under very hot conditions because stuff happens - dirt and dust clogging the heatsink fins, poor case ventilation, high room temperatures. *Because the manufacturer doesn't want returns. *Since the Pentium 90 Intel CPUs have been protected from damage caused by overheating. *That is probably now true for recent AMD CPUs. The ability to overclock depends on the individual processor, motherboard, heat sinks, ventilation and power supplies stability. *The maximum room temperature for proper overclocked or non-overclocked operation depends on the same things. Phil Weldon "baggins2000" wrote in message ... What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. *I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. |
#7
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Maximum room temperature
'Phil Weldon' wrote, in part:
'baggins2000' wrote: What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. _____ The short answer - it depends. The maximum room temperature allowable depends on how good your heat sinks and case ventilation are. _____ CORRECTION; the fourth sentence in the third paragraph of my reply should read: That improvement gives a 'SMALLER' temperature difference between the air entering the heatsink and the CPU/GPU/chipset/memory. (emphasis added) My original reply incorrectly stated: That improvement gives a greater temperature difference between the air entering the heatsink and the CPU/GPU/chipset/memory. Phil Weldon "Phil Weldon" wrote in message m... 'baggins2000' wrote: What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. _____ The short answer - it depends. The maximum room temperature allowable depends on how good your heat sinks and case ventilation are. Very good heat sinks, along with good case ventilation will keep your computer running at a room temperature too high to be healthy for you (say, 50 C or 122 F). On the other hand your particular CPU heatsink/fan combination, other heat sinks, and the volume of air moved through the system case might NOT be good enough. A better heatsink (larger, more fins, more conductive metal, flatter/smoother/more parallel CPU interface, higher air flow, and perhaps internal heat pipes) will have a lower thermal resistance. That improvement gives a greater temperature difference between the air entering the heatsink and the CPU/GPU/chipset/memory. CPUs (Intel in particular) are designed to run properly under very hot conditions because stuff happens - dirt and dust clogging the heatsink fins, poor case ventilation, high room temperatures. Because the manufacturer doesn't want returns. Since the Pentium 90 Intel CPUs have been protected from damage caused by overheating. That is probably now true for recent AMD CPUs. The ability to overclock depends on the individual processor, motherboard, heat sinks, ventilation and power supplies stability. The maximum room temperature for proper overclocked or non-overclocked operation depends on the same things. Phil Weldon "baggins2000" wrote in message ... What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. |
#8
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Maximum room temperature
'Phil Weldon' wrote, in part:
'baggins2000' wrote: What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. _____ The short answer - it depends. The maximum room temperature allowable depends on how good your heat sinks and case ventilation are. _____ CORRECTION; the fourth sentence in the third paragraph of my reply should read: That improvement gives a 'SMALLER' temperature difference between the air entering the heatsink and the CPU/GPU/chipset/memory. (emphasis added) My original reply incorrectly stated: That improvement gives a greater temperature difference between the air entering the heatsink and the CPU/GPU/chipset/memory. Phil Weldon "baggins2000" wrote in message ... Thanks, for the info I'd would have to rate this as the best set of responses in 8yrs. Very informative. Maybe needs another post, but you mentioned Zalman fans. I have one, but I am not that confident that I put in on correctly. Do you have a recommendation on procedures for installing Zalman fans or just about any of these larger fans. I'm always worried I'm going to install this thing a little off of the chip. The first time I tried to install it looked like I had left a 1/4 of an inch off of the chip and the whole chip wasn't covered. And on one fan I'm having a heck of a time checking the position (Zalman CNPS 7700 ALCU). On Feb 19, 6:04 pm, "Phil Weldon" wrote: 'baggins2000' wrote: What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. _____ The short answer - it depends. The maximum room temperature allowable depends on how good your heat sinks and case ventilation are. Very good heat sinks, along with good case ventilation will keep your computer running at a room temperature too high to be healthy for you (say, 50 C or 122 F). On the other hand your particular CPU heatsink/fan combination, other heat sinks, and the volume of air moved through the system case might NOT be good enough. A better heatsink (larger, more fins, more conductive metal, flatter/smoother/more parallel CPU interface, higher air flow, and perhaps internal heat pipes) will have a lower thermal resistance. That improvement gives a greater temperature difference between the air entering the heatsink and the CPU/GPU/chipset/memory. CPUs (Intel in particular) are designed to run properly under very hot conditions because stuff happens - dirt and dust clogging the heatsink fins, poor case ventilation, high room temperatures. Because the manufacturer doesn't want returns. Since the Pentium 90 Intel CPUs have been protected from damage caused by overheating. That is probably now true for recent AMD CPUs. The ability to overclock depends on the individual processor, motherboard, heat sinks, ventilation and power supplies stability. The maximum room temperature for proper overclocked or non-overclocked operation depends on the same things. Phil Weldon "baggins2000" wrote in message ... What would be the recommended maximum room temperature for operating an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to overclock, but I guessed that people here would know more about the thermal aspects of CPU operation. |
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