Atomic I/O letters column #42
Originally published in Atomic: Maximum Power Computing Reprinted here February 2005. Last modified 16-Jan-2015.
Performance anxiety
The new reduced monster closet Doom 3 expansion will be out soon, so I'm finally going to get the game. I'm forced to evaluate my PC's performance and determine what, if anything, needs upgrading.
I'm running an Athlon 64 system on an MSI K8T Neo motherboard, so that seems fine. My video card is a 128Mb Radeon 9800 Pro, which also seems fine. Unfortunately, my RAM is a 2 x 256Mb kit of Kingston ValueRAM. CAS 3.0, slow everything. So it seems I have two upgrade paths, since I'm budgeted to as close to $AU200 as possible.
Path 1 - grab a 512Mb stick of ValueRAM, bringing my total RAM to 1024Mb. Two problems; firstly, will this be compatible with my current setup and finally, is the slow response time going to become a problem in the next generation of games?
Path 2 - grab 512Mb of sexy RAM. Obviously I'll have to remove my current RAM, so I'll be stuck on 512Mb, but it will be fast. Two problems again; is this enough RAM? And which RAM to choose at the $AU200 mark?
Joshua
Answer:
People always ask this kind of question just before some hotly anticipated
new game comes out, and I always give the same basic answer:
Get the game. Play the game. See if your PC actually does suck. If it does, upgrade. If it doesn't, save your money. Don't upgrade first.
Someone with a PC which doesn't make it even to the minimum requirements for running Doom 3 (GeForce3/Radeon 8500, any old P4 or Athlon XP, 384Mb RAM, $AU2.20 worth of spare hard disk space) has a case for upgrading before buying. You, however, should be fine on all counts; as you say, you're only a bit short of RAM, if anything.
The timing of your RAM can make a difference to game performance, but it's not likely to make enough of a one that you'll be able to perceive it. Video card, CPU, and quantity of RAM matter, and the clock speed of the RAM can have a significant impact, but the RAM timings are much less important.
The RAM that takes a real pounding when you're playing a game is the video memory on the graphics card. Even if you've got a PCIe system with an x16 graphics card that gives you "AGP 16X" video bus speed, you'll still lose a ton of frame rate if the video card runs out of RAM.
Doom 3 certainly can be a monstrous video memory hog if you use uncompressed textures, but upgrading your system RAM won't help a great deal with that. You'd have to get a whole new 256Mb video card, which wouldn't be a cheap proposition even if you took leave of your senses and only upgraded to a mere 256Mb Radeon 9800.
There's a further kink, here. If you're running DDR400 (PC-3200) DDR memory at the moment, your three-slot motherboard will choke you back to DDR333 (PC-2700) speed if you fill its memory slots with most combinations of three memory modules. Only three single-sided modules, or two singles and one double, are meant to work at DDR400 speed.
Thankfully, this is explained in the manual (page 2-11 of the one I just downloaded), but the manual won't tell you how many "sides" your current modules have, and you can't tell just by looking. Your current modules are probably double-sided, though.
So, to repeat: Get the game, play the game, and make your upgrade decision then. Don't join the ranks of the few, the proud, the unnecessary early adopters, with a drawer full of curled up and yellow Half-Life 2 vouchers.
Chip chilling
After receiving my big paycheque the other day, I've decided to spend it on cooling my XP 2500+. While searching for HSF alternatives, I found these neato cooling plates called Peltier TECs that claim to make one side go sub zero and the other over boiling point, making my CPU very cold, but requiring some excessive cooling power on the opposite side.
The big question is, should I use an expensive HSF (Gigabyte 3D Cooler Pro or Thermalright SLK) to cool the TEC, or use a full water cooling system to keep the XP 2500 running in the safe zone?
Nick
Answer: Actually, few Peltiers can manage to be freezing on one side and boiling on the other. You can have one or the other, but not both, because the maximum temperature difference they can manage from one side to the other is well under a hundred degrees Celsius. You can stack Peltiers to get bigger differentials, but that severely reduces their total thermal transfer capability; it's not a workable solution for reasonably hot loads like most PC CPUs.
The only way you're going to be able to get a Peltier on your processor to work reasonably well is with water cooling, because your Athlon XP can be counted on to pump out something like 60 watts when it's working hard. A really big and/or really loud air cooler can deal with the hundred-watts-plus that'll result from Peltier-pumping that much heat, but it probably won't be able to keep the hot side of the Peltier cool enough to make the whole job worth doing. So water it'd have to be.
With a single really beefy Peltier - maximum power transfer well over 100 watts - you could make it happen; those Pelts are pretty easy to find these days. Unfortunately, I think they all want to run from 24 volts to give you full power, which rules out running one from your PC PSU. The alternative is two or more parallel 12 volt Peltiers sandwiched between copper cold plates, but that's hard to mount to a CPU, and the aggregate current draw is probably going to require another PSU, anyway.
And then there's waterproofing to deal with condensation, and doing something to stop your computer from burning its CPU socket off if the Peltier or the water cooling fails.
I wrote a couple of pieces about Peltiers a few years ago. Some of the numbers are a bit bigger these days, but the basic deal is the same.
Interior decorating
When I was applying thermal paste to my CPU, I accidentally trod on the thermal paste sachet and it squirted on my carpet. It's now been there for about a month because I've been too busy to clean it. It's not pushed into the carpet, and looks damn hard to get out - any ideas on how I would remove it? Are there any solvents that will help clean up thermal paste?
Tate
Answer: Oh, there are plenty. Alcohol, naptha (lighter fluid), and various others. Just squirting solvent on the stuff will only cause it to soak into the carpet, of course, and vacuuming up the liquid with a wet-and-dry vac is a very bad idea in the case of flammable solvents (The Do It Yourself Indoor Flamethrower!). Only if your vacuum cleaner is explicitly made for such tasks should you attempt it.
Rather than try non-flammable but probably still very evil solvents (1,1,1 trichloroethane, Liquid Paper thinner, would do it, but probably also dissolve synthetic carpet, and require a whole lot of room ventilation to avoid poisoning you), you could try cleaning the area with a sponge moistened with alcohol, then using carpet cleaning powder to get the rest. Simple salt or cornflour or something might work for this, but I'm not about to try the experiment myself to find out.
Is black better?
Recently, as part of our electronics course, we learned about the properties of heat sinks. The course notes (and exam mark schemes) claim that to make a heat sink more efficient it should be painted matte black.
I understand that this would make it more efficient, but my friend and I wondered why CPU heat sinks are not painted matte black? Most other heat sinks (attached to amplifiers etc) seem to be painted in this fashion, so why not CPU heat sinks?
Peter
Answer: Your course notes are right, and they're wrong.
A black object will, all things being equal, radiate heat better than one of any other colour. However, painting a shiny heat sink black may do nothing, or less than nothing, for its thermal performance, because the layer of paint acts as an insulator. The black colour must be an integral quality of the heat sink material, or a very thin, thermally-conductive layer on the outside; black-anodised aluminium is a perfect example of a good black heat sink material. It's possible to put a useful thermal black patina on copper by putting it in a hot sodium hydroxide and sodium chloride solution bath (also useful for disposing of corpses!), but that's neither a quick nor an easy process, so people usually only bother doing it for copper that's being used as a thermal absorber, as in solar water heaters, not on heat sinks.
This is because the colour of the heat sink matters less and less the more air you move over it. If the sink's hanging in vacuum (like the heat radiators on spacecraft that stop their own waste heat from boiling them) then it must be matte black; if it's sitting on earth being cooled by convection then it should be matte black; if it's got a bunch of forced-air cooling from an attached fan then it doesn't matter a great deal what colour it is.
Again, all things being equal, a shiny aluminium heat sink with a fan on it won't work quite as well as a black one - but the difference will be small enough that the extra marketability of the shiny heat sink is likely to be the deciding factor.
A shiny fan-cooled copper heat sink, which can't easily be made black without pointless insulative paint, will work better than an aluminium one with the same dimensions, thanks to copper's rather higher thermal conductivity.
