Building Linux Appliances - Dealing with Heat Issues?

wyrfel asks: "I'm going to build a router & switch based on LRP on the software side and on a FIC PA-2005 with Pentium 200 on the hardware side. Having read some discussions and wanting to make the system as quiet as possible I've remove everything except the floppy (which will be removed once the system is up an running), CPU and RAM from the board, lowered the boards speed from 66MHz to 50MHz which brought down CPU speed to 150MHz, did cut of the power supplys fan and lowered voltage of the CPU fan to 5V instead of 12V. So far everything seems to work fine. The power supply gets a bit warm on the top but it seems to be ok. I didn't add any PCI / ISA cards yet, so I wonder if doing so would bring problems through higher power consumption. What I really worry about is the heatsink that is placed directly beneath the CPU heatsink and that gets a bit hot when running the CPU fan with 5V. With 12V it's fine because of the extra airflow that comes from the fan located near that heatsink. BTW it is attached to some tiny piece labelled 'LINFINITY LX8382A'. Can someone tell me if I have to worry about it becoming too hot and if so what means 'too hot'? Any hints or further suggestions?"

Comments

If it's a Pentium, I wouldn't worry about heat

[ObviousGuy]

Heat wasn't the issue with the original Pentiums. Bad math was.

Unless you're clustering a bunch of these in a small space, it should be fine.

Re:If it's a Pentium, I wouldn't worry about heat

[Yarn]

with the original ones (P60, P66) it was a MAJOR issue. I mean, they had to fit fans on them.

At the time, this was seen as a sign of poor chip design ;)

Re:If it's a Pentium, I wouldn't worry about heat

[unitron]

But if you had one of those original Socket 4 Pentiums with a big heat sink and no fan it made an excellent waffle iron.

If you can still touch it for 5 seconds w.o pain

[Yarn]

It's not too hot.

I mean, it's not fair to ask your CPU/etc to go through something you wouldn't do yourself.

Be careful though, I once got a blister on my right index finger from a P3 heatsink with a failed fan, couldn't write for days

Oh lordy, I'm high as hell

[TimMD909]

Anyhoo, enough about me... you need to Google more often. Several helpful links:

Hot Spot - How Modern Processors Cope With Heat Emergencies - Goes over different bad things that can happen. It seems newer CPUs are designed to know when it gets too hot and will hang themselves to protect the hardware.

The Heat Sink Guide: Maximum CPU temperatures - Gives ya the maximum temperature before your CPU's inards are like melted butter. But it seems 60 degrees celcius is ok (140 degress fahrenheit).

Seriously man, whip out your Google when you don't know what to do
... or do you run Windoze? j/k :)

Ditch the old hardware

[shoppa]

I fully appreciate your desire to use older hardware rather than throw it away, but you've got to decide whether use old hardware is your goal or if build a small quiet appliance is your goal.

There are a large number of recent motherboards with NIC's on-board and low-heat CPU's (like the Via C3) widely available right now for really little $ if you want a PC-clone (e.g. ATX) form factor solution.

If you want even more reliability and efficiency, along with very much improved configurability, ditch the ATX stuff completely and go to PC/104.

Or - best of all - ditch the heat-hogging Intel-compatibles and go with a true low-power embedded CPU. See the usenet newgroup "comp.arch.embedded" and get up to speed :-)

Re:Ditch the old hardware

[Brownian Motion]

I'm doing the same thing right now, and the junk PC I'm using is loud, at least next to my other machines that I've spent the time/$ quieting.

When I get everything configured, I plan to replace the hardware. Via just released the EPIA 5000 and 800 boards. The Epia 5000 has on board LAN, sound, and video. The CPU is not speedy, it's about the speed of a P233, but requires no active cooling. The total is $98. You can't upgrade anything (CPU is surface mounted) and you only get one PCI Slot. But, depending on what you're doing, it can fit the bill. If you need more speed, $10 more gets you the Epia 800 (though it needs a small fan). If you need more power/PCI slots, you can upgrade to using a Micro-ATX board and use a VIA C3 (also needs minimal cooling)

You can get a Mini-ITX case w/ the power supply external (so no heat inside the case, and still no fan) for $72 (of course there are other neat cases). Toss in some memory, a network card, and some disk and you're done. I'm just going to put in a normal HD, it shouldn't be used much. If it makes too much noise I'll replace it with a laptop drive or a baracuda.

I'm going to add a USB-Ethernet adaptor ($5) so I can segment off my wireless base station. It should be more than fast enough to keep up (I'll know next week). I'm still looking for a working OS X VPN solution. I want to firewall off the wireless and use a VPN to get though the firewall. I might have to wait for Jaguar for that. Then I could use IPSec (hopefully the Epia 5000 is fast enough to handle IPSec over wireless.).

While this costs more than what you've got lying around, it's more than fast enough for a router and it'll be totally silent.

Lower the CPU multiplier, not only the FSB

[Papineau]

On those old CPU's, it was the motherboard only which was saying what was the multiplier to the CPU. By decreasing it (probably jumpers, might be dipswitches) to 1.5-2, you still have enough juice to do the routing/firewalling/NATing, but the power consumption will be quite lower (power is directly proportional to frequency for the same core). Or get a more massive passive heatsink: there were some Pentium 166 shipped with only a passive heatsink (HP I think, could be Compaq or Dell or any combination of the above).

Quiet fan.

[walt-sjc]

Um, just use a very quiet fan.Don't go really small as they seem to make more noise. Search for one with the lowest dB number. It will probably have a lower RPM and less severe pitch angle on the blades (which means thinner too.) A squirlcage style fan can be very quiet.

I'm also confused about the "heatsink under the heatsink" comment. Do you have stacked heatsinks????? WTF?

On some old (Micron) pentiums, they were using Massive heatsinks instead of fans. You would want to make sure that the fins are oriented vertically. Have vent holes in the bottom and top of the case (heat rises ya know..) If you are using a really small case, you may need a fan just due to the density inside the box. The samller cases had problems with heat buildup.

Want to catch the house on fire?

[zulux]

Unless you *really* know what your doing - leave the cooling alone. The last thing you want is a cheapo power supply overheating and catching the case on fire. If you have to have a quiet power-supply, Antec makes a line of AT and ATX power-supplies that have a fan that adjusts it's speed to the required cooling load. With your underclocked system, I doubt it reach past 20db.

VIA's Eden x86 Platform

[Jagasian]

VIA makes a motherboard + CPU + couns + gfx + ethernet platform that sells for about $80. The CPU is like a Crusoe in that it runs x86 apps, but is based around ultra low power consumption. The board is called Eden and it is tiny! You can buy a little tiny chasis to go with it. The chasis should adhere to the new mini-itx standard which is about as small as 7 CD jewel cases stacked ontop of eachother. Anyway, most of the chasis come with fanless DC powersupplies. So you can easily build a fanless x86 linux box with a gig of RAM, a 566mhz eden CPU, sound, graphics, and networking (TV-outs too) for a few hundred. If you really wanted a complete solid state machine you should stick a flash disk IDE harddrive in it.