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 Post subject: Athlon XP 1800+ Issues
PostPosted: Mon Jan 13, 2003 10:58 pm 
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Joined: Mon Jan 13, 2003 6:33 pm
Posts: 82
Location: St. Louis, MO
I have my CPU clocked at 1.1Ghz instead of the stock 1.533Ghz since my FSB is running at 200Mhz instead of 266Mhz. Is this type of underclocking conducive to heat reduction? If not, where could I change the actual voltage? (I have a Gigabyte GA-7VRXP Rev 1.1, and my BIOS doesn't let me change voltages).

Has anyone been able to run this particular CPU (or one of higher a rating) in a near fanless system?

I'm using a Swiftech MCX-462U with a PC Power & Cooling Silencer blowing OUT from the heatsink and Arctic Silver III.

Motherboard Monitor is reporting a 62C temp on Sensor 2 (I'm guessing this is my CPU), a 46C temp on Sensor 1 (I'm guessing this is my case), and a -55C on Sensor 3 (Something wrong here?).

Is there anything I can do to improve my temperatures?

I have another Silencer and my PSU exhausting air, but no intake fans (Alternatively, I've opened a 5.25" and 3.5" bay as intake vents).


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PostPosted: Mon Jan 13, 2003 11:20 pm 
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That's a significant underclock & should mean a proportionate drop in dissipated power; your temps seem high. Swiftech HS installation is usually foolproof, but you might want to double check -- unless you're severely undervolting the fan? what's your ambient temp?

If no Vcore adjustment in the BIOS, short of major mod work, you're out of luck. Try the fan blowing down; it's usually more effective.


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 Post subject: Re: Athlon XP 1800+ Issues
PostPosted: Mon Jan 13, 2003 11:46 pm 
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Joined: Thu Nov 28, 2002 5:07 pm
Posts: 809
Location: London, UK
pandamonium54 wrote:
I have my CPU clocked at 1.1Ghz instead of the stock 1.533Ghz since my FSB is running at 200Mhz instead of 266Mhz. Is this type of underclocking conducive to heat reduction? If not, where could I change the actual voltage? (I have a Gigabyte GA-7VRXP Rev 1.1, and my BIOS doesn't let me change voltages).


I done this with a XP 2200+ 1800Mhz and clocked it down to 1333Mhz @ 200Mhz FSB instead of 266FSB, I did notice a drop in tempertures but it was only by a 2-3C difference. If I could undervolt it would probably make a little more difference, so it is more effective when done together if possible. :D


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 Post subject:
PostPosted: Tue Jan 14, 2003 12:01 am 
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Joined: Sun Aug 11, 2002 3:26 pm
Posts: 90
Location: Santa Clara, CA
Quote:
I'm using a Swiftech MCX-462U with a PC Power & Cooling Silencer blowing OUT from the heatsink and Arctic Silver III.


the MCX-462U is not meant to to be in a suck configuration, at least not without modificaiton. if you want to increase the sucking performance, give the fan clearance from the heatsink (at least 1/4-1/2 inch) and shroud the fan and a fraction of the top of the heatsink to prevent air from only moving only over the coolest part of the heatsink.

otherwise, i suggest changing the fan back to intended configuration for the MCX-462U, that is, blowing into the heatsink. for the same amount of airflow, exhaust turbulance of the fan is quieter than intake turbulance, which is usually another reason to blow instead of suck air into the heatsink.

this may explain your less than stellar cooling.

an unconnected sensor can show invalid values. this may explain sensor 3.

hope this helped.


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 Post subject:
PostPosted: Tue Jan 14, 2003 4:47 pm 
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Joined: Mon Jan 13, 2003 6:33 pm
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Location: St. Louis, MO
Well, if I clock it at stock speeds my sensor 2 reading tops out at about 69C idle and rises to 75C+ after I stress it with UT2003 for more than 5 minutes. (roughly speaking)

My ambient temps are around 22-24C - I think a major issue is my case temp (since I leave this machine on 24/7). I'd like to cool my case but it doesn't have any intake fan brackets so I'd have to do heavy modding to make that happen.

I'll try changing my fan orientation, but my exhaust fan (also a Silencer) is located right next to the CPU fan and I'm concerned that doing so will impede both exhaust and cooling. Additionally, I reasoned that if my CPU fan was sucking air up, a good portion of the hot air would be immediately exhausted. Here's a side diagram:
Code:
     exhaust fan
      /
  < ] <
         /\
        -----   <- cpu fan
        -----   <- heatsink/cpu/mobo

There's about an inch of space between the top of the CPU fan and the bottom of the exhaust fan.


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 Post subject:
PostPosted: Tue Jan 14, 2003 7:08 pm 
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Posts: 809
Location: London, UK
It is better to blow down rather than up on the HS. The problem is that low speed fans / low noise does not suck as well as it blows. This method will not remove the heat from the HS as effective.

Let me give you a example, it is like having hot food that is hard to touch/eat. What do we do? we blow on it, imagine we try to suck the heat out of it, it is far more difficult. Try it with a fan and it will take ages to cool your food down by sucking air up. Now blow down on it and your food almost seems instantly cool.

You will likely see an increase in tempertures, so be careful to have your system to shut down automatically at a certain point or you could "fry your chiips". :lol:


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 Post subject: Re: Athlon XP 1800+ Issues
PostPosted: Wed Jan 15, 2003 7:19 am 
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Joined: Tue Jan 07, 2003 7:34 am
Posts: 14
Location: Rome, Italy
pandamonium54 wrote:
I have my CPU clocked at 1.1Ghz instead of the stock 1.533Ghz since my FSB is running at 200Mhz instead of 266Mhz. Is this type of underclocking conducive to heat reduction? If not, where could I change the actual voltage? (I have a Gigabyte GA-7VRXP Rev 1.1, and my BIOS doesn't let me change voltages).

Has anyone been able to run this particular CPU (or one of higher a rating) in a near fanless system?

There is a linear relationship between clock speed and power consumption, whereas the relationship between voltage and power consumption is quadratic. This is why undervolting is more effective than underclocking at reducing heat dissipation: the big gain is from undervolting, and the underclocking is mostly necessary so that the CPU is able to work at the reduced core voltage.

All thing being equal, underclocking the FSB from 133 MHz to 100 Mhz results in a 25% drop in heat generation, which in turn should result in a 25% decrease in the difference between core temperature and ambient temperature. The actual power consumption of an Athlon XP depends on what type of core it has. The newer Thoroughbred chips generate much less heat than Palominos, especially the "B" revisions.

As regards being able to run fanless, I doubt it. Even if you have a Thoroughbred "B", AMD's datasheets say power dissipation is 46.3 W at 1533 Mhz. At 1.1Ghz, it should be about 34.7W, which sounds too high for fanless operation.


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 Post subject:
PostPosted: Thu Jan 16, 2003 3:16 pm 
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Joined: Sun Jan 05, 2003 12:09 pm
Posts: 279
Location: U.K.
How about putting the cpu fan in a place where it can get fresh air, blowing into a duct that leads down to the heatsink? I imagine that would help. Still, even as things are I feel sure you'll see cooler temperatures just by turning the fan so it blows.


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 Post subject:
PostPosted: Thu Jan 16, 2003 6:42 pm 
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Joined: Sun Oct 13, 2002 12:48 pm
Posts: 11
I also have an XP 1800 with a MCX462. It is on a soyo dragon plus motherboard with pretty much default bios settings. I have it in a mid tower aluminum (coolermaster) case: 1 panaflo in, 1 panaflo out, 1 panaflo out of the blowhole. The 462 has a panaflo. All panaflos are 80mm, 2000 rpms.
Also a seagate iv 80gb, a generic cd-rw, geforce 3, seasonic 300w powersupply. Removed motherboard fan and replaced w/heatsink.

cpu temp (motherboard monitor) runs at 48C idle here in sunny southern california.

It's not the quietest system but it is stable.


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 Post subject:
PostPosted: Fri Jan 17, 2003 1:10 pm 
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Joined: Sun Aug 11, 2002 3:26 pm
Posts: 86
Location: Falun, Sweden
Quote:
Is there anything I can do to improve my temperatures?


How about running a program like VCool? I don't know if they work for your motherboard, but they work for any VIA KTxxx board at least. My temperature drops around 20°C when idle and the northbridge is shut down.


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