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?"

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

Beware the dust puppy!

[Faré]

I have built a router out of a P75 (oc'ed to 90 MHz!), but I recently lost its IBM harddrive. When I opened the case, I it was full of an inches-high structure of dirt. Most probably, the bad ventilation of the case caused the dust to accumulate which in turn prevented heat circulation and contributed to overheat the fragile drive.

The morale of the story is twofold:

• most importantly Always keep up-to-date backups of everything you could hate to lose
• be sure that dust doesn't accumulate inside your case. Think about it before removing fans, and check once in a while that dust didn't invade your computer.

Actually

[Rope_a_Dope]

It becomes increasingly difficult to determine if your processor is too hot, because often times you only get erratic strange behavior. This happens with synchronous chips because the clock cycle tells the controller when to expect results from the chip.
When the chip becomes hot, the data paths on the chip become longer (heat expands things) and the data expected to be coming out of the chip at the end of that clock cycle might not be accurate.
The best way to test the thing is to wait til it gets about as hot as you think it's going to get, and then start feeding it complex math equations (which you presumably would know the correct answer to). If they turn out correct, you can assume its operating within spec.

Re:

[account_deleted]

Comment removed based on user account deletion

Voltage regulator

[cyr]

I bet the heat sink you're talking about is for the CPU voltage regulator, and if it's an old linear regulator it can dissipate *a lot* of heat, in fact if your input voltage is 5V (AT PSU) and the core voltage is 2.8v (Pentium MMX) the regulator will dissipate almost as much heat as the CPU!

I would try mounting the fan so that more air flows across the regulator heatsink, or get another board with a switching regulator.

had router with fli4l

[dunkelfalke]

i had a router i built with the fli4l (www.fli4l.de) linux isdn+dsl router distribution. it was a p133 downclocked to 75 mhz on some asus dual pentium board with eisa (the only motherboard what i had). i actually ripped off all fans, the psu fan, the cpu fan, everything and it worked without any issues. yeah, it was quite warm but not too hot. nothing where you could burn your fingers.

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 [64.186.164.229]. 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 [64.186.164.229] (so no heat inside the case, and still no fan) for $72 (of course there are other neat cases [64.186.164.229]). 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).

Re:Lower the CPU multiplier, not only the FSB

[Atrahasis]

I've recently bought a Dell P166 which has only a pasive heatsink, although the PSU is positioned so that the heatsink is by one of it's intake vents, so its cooled (very slightly) by that.

Re:Lower the CPU multiplier, not only the FSB

[afidel]

I run a pentium 133 underclocked to 120 without even a heatsink, just bare chip. Under load as a firewall/router/nat box I can keep my hand on it all day long, this is just the bare board attached to the wall through the post holes.

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.

you worry too much

[Kafteinn]

I was until recently running a 200mhz downclocked to 150mhz computer with a screwdriver stopping the power supply fan from making any noise and no fan at all on the cpu.

It had 1 pci nic and 2 ISA (I was using it as a hub)
It ran fine for months until I finally found a great 12 port 10 mb/s hub in a dumpster. (Yes, I'm poor =)

LX8382

[linuxator]

LX8382 should be voltage regulator...

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.

Bump cpu fan speed by 2 volts

[SpaceLifeForm]

Rewire the power to the cpu fan to run it at 7 volts.
See http://www.overclockershideout.com/7voltmod.shtml [overclockershideout.com]

www.soekris.com

[darrylo]

For small routers/firewalls (and if you don't mind spending a modest amount of money), check out the small PC-compatibles from Soekris Engineering [soekris.com]. Their (well, his) main product is a small PC-compatible board designed for routers/firewalls: a 133MHz 486 class processor (AMD ElanSC520), 64MB RAM, three (3) LAN ports, a type II compact flash socket, BIOS, and a serial console port. Note that there's NO video, sound, or IDE ports (you boot from LAN or from the compact flash port, which can be used with an IBM microdrive). It's low power (under 20 watts), very quiet (no fans), and pretty small. Cost with metal case and US wallwart power supply is something like $250 plus tax and shipping (bare boards are available, too). In the past, availability has been a bit intermittent ("in stock" maybe once a month), as they seem to sell out their incoming production batches fairly quickly, so be warned.

Also, I believe that they're about to ship a version with PCMCIA slots (but only two LAN ports), basically designed for people to build wireless access points/firewalls.

People have FreeBSD and Linux (I think) currently running on it. I bought one to create a FreeBSD-based home firewall, and it's pretty cool (I haven't yet deployed mine, but I'm getting close). There's also a mailing list (check out the web site).

However, if you need video, sound, or IDE ports, one of the Shuttle boxes might be a better match (although they'll probably use up a lot more power).

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.

p133 runs fine for me

[HTD]

somebody gave me an old compaq presario with a Pentium 133 cpu. It has no fan on the cpu, but some huge metallic radiator. The powersupply was so quiet that i first thought it doesn't work (these old compaqs take a few secs before they display something on screen).
Anyway the box now runs with 3 realtek pci nics and floppyfw w/o any problems.
I think u can remove the fan from your cpu and replace it with some real big metallic cooler like the Mac G4 machines have inside. dunno where to get such things though (from old compaqs, hehe).