Is underclocking/undervolting worth it for me?

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sonuvbob
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Is underclocking/undervolting worth it for me?

Post by sonuvbob » Thu Jun 02, 2005 9:15 am

Let me start by saying that my primary concern at the moment is lowering the overall heat output of my comp, especially when (mostly) idle, while still being able to switch to a decent gaming rig with just a reboot.

I've done a lot of fiddling with my xp-mobile 2400's settings over the past week, ending up at 667MHz (5x133) at 1.1v (default is 1.8GHz - 13.5x133 at 1.35v, though I'd prefer 1.6GHz - 8x200 @ ~1.2v - for synchronous RAM). And really, it hasn't done a whole lot of good for heat. My CPU (socket I think) temp's dropped from 35-36C idle, 39-40C load to 34-35C idle, 37-38C load, and my case temp's dropped maybe 1C.

Maybe my good case cooling and mediocre cpu cooling can account for the poor temp drop, but it still seems to get nearly as toasty in the room as it did before. So what I'm wondering is, (1) when you've already got a fairly cool cpu, does reducing its heat output even make a significant difference in the total heat output of the computer?

Also, (2) does FSB make a noticeable difference in heat? (Like 10x100 vs 5x200). Higher FSB does seem to need more voltage (Can't boot at 9x200 at 1.35v)

Specs:
P/S: Enermax EG365P-VE(FM) 350W
CPU: XP-Mobile 2400+ 35W
M/B: Abit NF7-S v2
RAM: 2x512MB Corsair PC3200 - 2-2-2-5 @ DDR333, 2-2-3-5 @ DDR400
Vid: Sapphire Ultimate Radeon 9600XT
Snd: E-MU 1820M (*)
HD1: Seagate ST3200822A
HD2: Seagate ST3120826A
Other: NEC 3520A DVD+/-RW, Floppy

(*) a HUGE source of heat, but it won't be around for long. (3) From a heat viewpoint, would I be better off using onboard sound, or a Turtle Beach Santa Cruz? I've heard the onboard sound creates quite a bit of heat.

sthayashi
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Post by sthayashi » Thu Jun 02, 2005 6:21 pm

At this point, I've got to know why you're so worried about heat. Your CPU temps are nothing short of awesome.

Anyways, I think you know the answer to 1) No, it's not really worth while to reduce the power output of an already low-powered CPU.
2) What's noticeable? Any difference it makes is within the margin of error on typical sensors
3) I really don't know, but I know that neither is significant on its own.

I'm going to speculate that you're worried about heat because it's f***ing hot in your room. If that's the case, I would examine other sources of heat. In your case a 100W light bulb puts out more heat than your computer.

sonuvbob
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Post by sonuvbob » Fri Jun 03, 2005 10:47 am

Turns out my underclocked numbers were tainted a bit by a hot day and lack of a/c. At [email protected], the CPU socket and case temps are 33C/24-25C idle, 35C/27-28C load. And yeah, that's definitely nice. It's also a huge difference from the 35-36C idle and 40C load I get at full speed- that's when it starts getting toasty in here. So actually I disagree that it's not worth underclocking- I just wish I could change multipliers on-the-fly with this board so it wouldn't require a reboot to switch between slow and fast speeds.

I think the main reason I'm obsessed with heat is that my last setup was a Palomino XP 2000+, which the motherboard/power supply seemed to enjoy overvolting by 0.05-.075v. Even with CpuIdle, that thing put off a ton of heat. And after setting the xp-m up, it didn't seem to be all that much cooler.

Also, lowering overall heat makes the process of quieting/silencing everything a lot easier.

For 2), I'll take that as a 'no'. I was just curious if there was a real test done on it (I couldn't find one).

And for 3), I read a post somewhere (I think it was at SPCR) saying that the NF7-S's onboard sound raised temps something like 4-8C. That is pretty significant, and that's why I asked.

POLIST8
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Post by POLIST8 » Fri Jun 03, 2005 11:43 am

You're saying that you found somewhere here that using onboard sound increased the system's temp that much (4-8)???? That's crazy! I've never heard anything like that.

Glue a heatsink on the chip. LOL.

sonuvbob
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Post by sonuvbob » Fri Jun 03, 2005 11:58 am

Someone somewhere said it. I'm not crazy, honest! (It may have just been higher "idle" temps from increased cpu usage, I dunno) I can't find the post, so I guess I'll have to try it out myself sometime.

The Greek
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Post by The Greek » Fri Jun 03, 2005 12:52 pm

Your temps are nothing to worry about unless they are within 7-10*C of the max operating temperature. My CPU idles higher than yours goes full load!

And 40*C toasty?! Who told you that, that is cool for a CPU!

My full load temp is 56*C, idle 40*C...

sonuvbob
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Post by sonuvbob » Fri Jun 03, 2005 2:20 pm

I know I'm not even remotely close to dangerous temps, that wasn't my point. (Right now I'm 33C at full load running 5x166 at 1.1v, 24.5C room temp. I still don't know if that's socket or diode temp)

The issue was that, when the sensor reads in the region of 38-40C, the room temp starts going up considerably. I can't just crank up the a/c, since it's just this room that's hot. So I'm trying to reduce the overall heat coming from my computer.

I do appreciate being called crazy by everyone who responds to my posts though :D

Elixer
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Post by Elixer » Fri Jun 03, 2005 3:21 pm

8x200 @ 1.2 seems like a good compromise between heat and power. At this setting your processor should be giving off ~25W. At 5x166 @ 1.1 your power draw from the processor should be around 12W. Your video card will be giving off more power than your processor at this speed. So if you're really looking to cut the power you might try heavily underclocking your video card. Be warned though, some video cards become unstable if they are underclocked too far. Also, with temperatures as good as those you should slow your fans further if possible as this will also help your power draw (a little bit).

sonuvbob
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Post by sonuvbob » Fri Jun 03, 2005 4:18 pm

I'll probably end up somewhere between 5x166 and 8x200 most of the time, most likely whatever the fastest speed that's stable at 1.1v is. 3DMark2001SE ran fine at 8x200 at 1.15v (22.5W), but I didn't try a real cpu test.

According to X-bit Labs, my 9600xt's drawing about 9W at idle. And it's been idle pretty much the whole time I've had it, because it's got serious problems. It's getting sent back as soon as the new card arrives.

I'm replacing it with a 6600GT, which I've heard can be underclocked well in 2d. I'm sure it'll be hotter than the Radeon, but the gamer in me won out.

I just got an Aspire fan speed controller for my intake and exhaust fans. They're both noisy Panaflos (dunno which model, but at least 30dBA at 12v), and it makes a world of difference. I think the next step in quieting will be a new case with a couple 120mm fans.

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Post by sthayashi » Fri Jun 03, 2005 10:25 pm

sonuvbob wrote:I think the main reason I'm obsessed with heat is that my last setup was a Palomino XP 2000+, which the motherboard/power supply seemed to enjoy overvolting by 0.05-.075v. Even with CpuIdle, that thing put off a ton of heat. And after setting the xp-m up, it didn't seem to be all that much cooler.
Like I said, you're really not putting out that much heat. It is very much the equivalent of a lightbulb. If this alone is making your room excessively hot, then I would look into airflow techniques for the room. Opening a door and a window will allow air to pass through the room

Also, if you have a CRT monitor, it puts out more heat than your computer. Period. If you have a smallish one, it will put out only a little more heat, but if you have a 19" or 21" one, it will easily be hotter than your computer.

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Post by MikeC » Fri Jun 03, 2005 10:34 pm

How hot the room gets will not be affected by how well your CPU is cooled or how high your CPU temp sensor reads - because the amount of heat generated by the system is exactly the same. You may think the room is getting hotter when the CPU temp reads higher but this is probably purely psychological.

The Greek
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Post by The Greek » Sat Jun 04, 2005 3:03 am

I certainly agree with Mike, I seriously doubt your PC is making even a small difference in your room temperature. Mine sure doesn't and it runs a steamy 56*C (132*F) CPU temp and 38*C (100*F) case temp under full load.

sonuvbob
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Post by sonuvbob » Sat Jun 04, 2005 9:43 am

MikeC wrote:How hot the room gets will not be affected by how well your CPU is cooled or how high your CPU temp sensor reads - because the amount of heat generated by the system is exactly the same. You may think the room is getting hotter when the CPU temp reads higher but this is probably purely psychological.
What is it with people calling me crazy here?

I'm well aware that the cooling has little to do with it. Half the problem was that the case cooling was too effective- the hot air inside the case would get pushed out into my room. And I don't put much stock in the temps the sensors show, except as relative to other values from the same sensor (and even then taken with a grain of salt, since cooling and ambient temps can distort things).

So unless you're saying that there's no difference in heat output between at CPU at idle (with s2k d/c and whatnot) and at full load, or between 833mhz at 1.1v and 1.8ghz at 1.2v, I fully agree with you.

I didn't mean to imply direct causation between sensor reads and room temperatures. Just that when it's running at full load at full speed for a while (which happens to show up as 40C on the sensor), it pushes a lot of heat into my room. It doesn't seem like it should, given the specs, but it's hard to argue with a thermometer. With the old Palomino, there would be times when it was in the mid 80s (F, of course) in here, and in the high 60s in most of the rest of the house (Door open, ceiling fan on).

I do have a 19" CRT, a pretty big heat source, though I don't know how much heat transfers to the surrounding air (I guess I could test it by turning it off and seeing how long it takes to cool off). It's definitely going to go at some point, but that's going to be an expensive replacement.

Also, I don't know how much power my sound card uses, but the external dock thingy (powered by the internal card) gets hotter on top than my monitor sometimes.


Thanks Elixer and sthayashi for the advice, and thanks everyone else for calling me crazy :D

lm
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Post by lm » Sat Jun 04, 2005 9:56 am

sonuvbob wrote:Half the problem was that the case cooling was too effective- the hot air inside the case would get pushed out into my room.
Umm, all the heat that is generated inside the computer case HAS to come out, sooner or later. Otherwise the case temperature would rise with no limits until broken.

So the effectivity of your machine's cooling system shouldn't have any effect on your room temperature whatsoever, and the only thing that defines the effect on your room temperature is the total power used by the system, which can be measured with a power meter between the AC cord and the wall socket.

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Post by sthayashi » Sat Jun 04, 2005 10:07 am

sonuvbob wrote:I didn't mean to imply direct causation between sensor reads and room temperatures. Just that when it's running at full load at full speed for a while (which happens to show up as 40C on the sensor), it pushes a lot of heat into my room. It doesn't seem like it should, given the specs, but it's hard to argue with a thermometer. With the old Palomino, there would be times when it was in the mid 80s (F, of course) in here, and in the high 60s in most of the rest of the house (Door open, ceiling fan on).

I do have a 19" CRT, a pretty big heat source, though I don't know how much heat transfers to the surrounding air (I guess I could test it by turning it off and seeing how long it takes to cool off). It's definitely going to go at some point, but that's going to be an expensive replacement.
Maybe you should do a room temperature comparison with everything off. Some rooms ARE just plain warm due to no or bad airflow. The best ways I know for cooling a room w/o AC is to do the following:
1) Open a window that is directly across from a door, if possible. Otherwise, just open a window.
2) Leave the door open.
3) Open a window that is directly acros from the door OUTSIDE the room (if you have one. Otherwise just open a window that is not in the room).
4) Place a window fan in one of the open windows and turn it on.

This will turn your house or apartment into a small wind tunnel and you'll be doing to your room what your case setup does to your processor. This works better than just opening a door and turning on a ceiling fan.

Also, if you look on the back of the monitor, you'll see information about the power draw/consumption. Look around the room for other potential heat makers. Stereo equipment can sometimes be quite the heat generator too. Turn them off if you're not using them right now.

lm
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Post by lm » Sat Jun 04, 2005 10:57 am

sthayashi wrote:Stereo equipment can sometimes be quite the heat generator too. Turn them off if you're not using them right now.
My stereo amp that is capable of 2*75W output and connected to 2 large 3-way floor speakers uses less than 20W of power when listening to music on a reasonable volume... and that of course includes power used by the speakers. I think <20W is very little.

But if he had a class-a amp then it'd be different.

sonuvbob
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Post by sonuvbob » Sat Jun 04, 2005 11:58 am

Umm, all the heat that is generated inside the computer case HAS to come out, sooner or later. Otherwise the case temperature would rise with no limits until broken.
True, but it dissipates slowly without an exhaust fan, as does the heat in the room. So it gets pretty hot in the case while at full load, and the hot air keeps spreading out over the course of a couple hours or so after it's back to idle. As a result, the room temp doesn't go up as much. With an exhaust fan, all that heat is entering the room a lot faster, and unfortunately the room doesn't have enough airflow/cooling to handle it, so it heats up quite a bit...

Which brings me to sthayashi's post. Opening windows definitely helps when it's relatively cool outside. But when it's in the 80s out it's just going to heat up the house, isn't it (even with the wind tunnel effect)?

I have a register in the floor next to my computer, and an escape vent (or whatever you call it) near the ceiling on the opposite side of the room. Do you think I could get decent air flow by closing the door and having the ceiling fan pull air up? Would it need help from the central air fan?
Also, if you look on the back of the monitor, you'll see information about the power draw/consumption. Look around the room for other potential heat makers. Stereo equipment can sometimes be quite the heat generator too. Turn them off if you're not using them right now.
1.8A @ 100-120v :shock: I don't know how much of that becomes heat, but I would imagine it's nearly all. Soooo... how are LCDs for gaming and movie watching these days? :D

No stereo equipment hooked up at the moment, just headphones. Heat sources are: CRT, computer + audio dock, 3 60W bulbs, and a window that gets basically no direct sunlight this time of year. I would hope that the heat from the bulbs (mounted to the ceiling fan) stays near the ceiling, and that the hot air is pushed out the vent/door by the fan.

Thanks again, sthayashi

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Post by sthayashi » Sat Jun 04, 2005 2:02 pm

sonuvbob wrote:Which brings me to sthayashi's post. Opening windows definitely helps when it's relatively cool outside. But when it's in the 80s out it's just going to heat up the house, isn't it (even with the wind tunnel effect)?

I have a register in the floor next to my computer, and an escape vent (or whatever you call it) near the ceiling on the opposite side of the room. Do you think I could get decent air flow by closing the door and having the ceiling fan pull air up? Would it need help from the central air fan?
Central air is something I'm not as familiar with. Ceiling fans essentially stir air around, which will make you feel cooler, but won't necessarily reduce heat any faster.

Opening a window on a hot day will only make things warmer if the room is cooler than the outdoors to begin with. But moving air will feel cooler than still air (though by how much, who knows?).

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