Speed limits

Whenever I buy a new computer, I'm using benchmark programs like Futuremark's 3DMark03 to measure how much faster the new computer is than the old one. While benchmarks aren't 100% reliable to compare two nearly equal graphics cards, they are reliable enough to compare two very different computers. Because I usually buy a new desktop every two years, and Moore's law applies, my benchmarks usually tell me that the new computer is twice as fast as the last one. But that is only one very specific speed measured, in other respects the new computer is as slow as the old one. For example the time to boot up my computer from cold to ready to go hasn't improved at all in the last couple of years. So where are a computers speed limits?

Most people first look at the clock speed of the CPU. That is a bad old habit, which stopped being useful some years ago. When clock speeds were still measured in MHz, it told you something about the computers speed. Since we are in the GHz area, the clock speed is rarely the limiting factor. Also clockspeed has hit a ceiling just under 4 GHz, and isn't going up any more. So even for CPU speed the GHz aren't the important thing any more, two 3.4 GHz CPU's can have vastly different speeds, depending on other features like cache size, hyperthreading, or dual core technology. I usually buy CPU's which are several notches below the best, because you can usually get a CPU which is just 10% slower for half the price, and you'll never even notice the difference. For my new computer I went for a Intel Pentium 640 with 3.2 GHz and hyperthreading.

Far more important for gamers is the speed of the graphics card. Unfortunately that one is the most confusing, as there isn't any good unit to measure it. You have to rely on benchmarks, and then you get into the endless discussion on whether some graphics card producer tweaked his drivers to specifically perform well with a certain benchmark. One helpful thing is that recently there was a switch in technology from AGP bus graphics cards to PCI express ones. That change had a big impact on all possible benchmark values. So when buying a computer now, getting one with a PCI express card is a good way to guarantee a certain minimum performance. Beyond that, the speed of the card is best measured in dollars, the more expensive the card, the faster it is. Unfortunately not a linear scale, the top end cards are all overpriced. I usually take a card a notch or two below the top, but this time I indulged myself and got a Nvidia Geforce 7800 GTX with 256 MB of memory. That is currently the fastest card around, until inevitably ATI produces an even faster Radeon card. For twice the price you can now have two graphics cards working in tandem, but while this SLI technology is faster than just one card, it isn't twice as fast.

The longer you actually use a computer, the more evident it becomes that one major speed limit in your computer is neither the CPU nor the graphics card, but the memory. There are different speeds of memory, but even more important is the total amount of memory you have. There are still computers being sold with just 256 MB of RAM, and these are often horribly slow in many applications. Because as soon as the memory is full, Windows uses "virtual memory" on the hard disk, which is much, much slower. If you are doing something which shouldn't access any files, and the hard disk drive LED is flickering constantly, you got a speed problem there. 512 MB is an absolute minimum nowadays. World of Warcraft now uses so much memory, that with 512 MB you have some speed problems, and 1 GB is preferable. As the memory use has been going up fast in the last couple of years, I went for 2 GB of DDR2 667 RAM, the fastest RAM available. You can get computers with even more, but 2 GB should cover all possible games for the next couple of years, and only people working on graphics applications need more.

So will my new computer be lightning fast with these specs? Well, in the benchmarks certainly, and I will be able to run games at high resolution, anti-aliasing, best graphics settings and still get a very good framerate. But when I boot the machine up, it will still take a minute or so. Getting all the parts of a computer started up seems to take an awful long time, especially network components. And the hard disk is to blame for some of that delay. If you just look at the specs, hard disks are getting faster. But at the same time they are getting much bigger, and files are getting bigger too, so finding a file on the hard disk and loading it still takes some time.

Another big speed limit is the internet connection. I have a 3 Mbit ADSL connection, and surfing the internet is often still slow. First of all 3 Mbit is only the speed limit on my side, if you use an utility like DUmeter you can see that most data arrive at a much lower speed. If the server you are getting the data from isn't delivering at 3 Mbit (and few are), your 3 Mbit ADSL doesn't help you much, except for downloading several files in parallel. 3 Mbit is about 300 kByte per second, or about 1 GByte per hour, so really large files, like game demos or beta clients, still take some time even in the best of cases.

But while surfing or playing online games the speed limit is a different one. Every click needs to travel to the computer on the other side of the line, be processed there, and the response sent back. That takes at least the time described as "ping", usually around 50 ms if the server is on the same continent as you are, a couple of hundred milliseconds if the server is on a different continent. Sometimes your data get into an internet traffic jam, and take much longer.

So while playing World of Warcraft for example, any lag you observe can come from many different sources. You often have lag when arriving in an area with many other players, because lots of players with lots of equipment means lots of data. Your graphics card might be too slow to process them at a good frame rate, your memory might run over and start swapping on the slow hard disk, the server might have problems delivering data at this speed, the data might get slowed down on the way, or your modem might be slow in receiving them. Using older computers I observed some lag which didn't happen on a newer computer, so I'm hopeful that the new computer will pretty much solve all client side lag problems. But the server side lag, and internet lag problems will remain, and there is nothing I could possibly do about them. As everybody's computers are getting faster with the years, this speed limit will remain. If you got half a second of internet lag, it gets pretty noticeable in a twitchy game situation. This is one of the reasons for the "semi turn-based" style of typical MMORPG combat. I wonder if that will stay with us much longer, of if somebody will come up with a better solution to handle the possibility of lag.
- posted by Tobold @ 8:12 AM Permanent Link