[SPARCbook] Q: Heat build-up in SPARCbook3 GX "left on 24x7"

[Ian Spray]

On 23-Oct-00 Ken Hansen wrote:
> 
> The laptop sits on a hardwood table, with the rear portion "propped up"
> on those clever little "legs." I am starting to assemble my "lab," and as
> such will be moving the machine to some wire shelving in my basement (a
> relatively cool environment - I am thinking of placing a small 12 V. fan
> or two (from an AT&T UnixPC) under the SPARCbook to improve air-flow, has
> anyone else done such a thing?
> 
You might also like to try a small fan blowing into the PCMCIA sockets -
that will try to get air moving around the CPU itself.  Blowing under the
machine is a good alternative, as the CPU heatsink is thermally bonded to
the middle of the bottom of the case.  Placing the unit on a wire mesh rack
might also help (dunno the make, but similar to the stuff on ER), as the
large gaps let air move, and keeping the base in contact with the metal
allows the shelf to become a larger heatsink.

> Also, the laptop has remained open for he last two or three months, and
> while the display turns off after a period of time (great!), I know I
> can't close the case, as the keyboard seems to "vent" heat from the
> system - what are folks doing about this? Do they just leave them open?
> Didn't someone set some of these up as kiosks? How are you handling heat
> dissipation?
>
There is indeed heat vented from the top of the case.  I would imagine that
the kiosk problem is solved by not running SETI at home/dnetc or any other
process which keeps the CPU 100% active.  I have used a plain S3 (50MHz
CPU) as a firewall/NAT/router at home, and this summer it was running 24x7
in an ambient of up to 33C, with the temperature inside the PCMCIA socket
reaching 44.1C at the worst point.  This was allowing the kernel to clock
stop to keep the core temperature down, and it was also on a much slower
machine so the heat generated was much lower too.

I did have two unexplained crashes, but the rest of the time it just worked
- there were no external fans but I did leave the screen up to help move
the heat.  I would not recommend running a machine like this, especially
not with a PCMCIA modem card in it - pulling that out really was like
holding a hot potato.  I did make sure that the hard drive was spun down
after a fairly short time, but that was only because a firewall doesn't
need much disc access.

> One final question - by leaving my SPARCbook on 24x7, am I damaging the
> battery? The battery is installed, and the LCD shows battery life varying
> between 99% and 100% remaining... Is this drawing power through the
> battery or working independently? For long-term storage (I have a
> spare!), should I leave the laptop plugged in and turned off, or should
> I remove the battery and put it away? I am concerned an internal clock
> battery will give up the ghost and bring the SPARCbook down, with a
> broken clock battery...
>
The cycling is due to the charging being cut once the microcontroller
senses the end of charge signal from the battery pack.  After this, the
cells will start to loose energy as all rechargeable systems do, and once
it gets below the top threshold, the micro will turn the charging circuit
back on again.  You're just watching the hysteresis at the end of charge.

I'm not convinced that the main battery has anything to do with the clock
backup - they're supposed to be independant and self powered.  I do have to
add that I haven't read the schematics for the SPARCbook machines, so I
can't be sure.  I would be very surprised if a dying clock battery were to
crash the machine though :)


-- 
Ian Spray          :  Software Engineer     :  Tadpole-RDI
iws at tadpole.co.uk  :  +44 (0) 1223 428 224  :  http://www.tadpole.com/