Here is a short guide on tweaks that have helped improve A2's performance. I read up on other's tweaks and also ran resource monitors on my own rig and found some interesting and highly effective methods to increase A2 performance.
Hard Drive Performance:
Hard drive storage is perhaps the most major performance hit with A2.
If using a standard hard drive rather than a solid-state drive, you should migrate your entire A2 folder to the outer edges of your platters. You can do this with "Ultimate Defrag", a free download. Download from CNET
. Go into the options and add your Arma2 folder (the entire thing) to the high performance list. Run a "Consolidate" defrag and check the option for "Respect High Performance". Since A2 loads only bits of data from many of it's pbo files, a simple windows defrag can have your hard drive seeking half-- or even full sweeps as it reads one pbo or another that is placed randomly around the drive.
If you have a solid-state drive, defrag will do little to nothing other than use up your drive faster.
Another trick to make things simpler is using multiple drives and partitioning. If you have two drives, load your OS on one and A2 on the other. Put your swap file on both, windows will stripe your swap across the drives automagically and increase performance that much more.
If you want to use partitioning for very simple high performance/low performance seperation, you can split the target drive 50/50. The first partition will be the high performance drive, the second will be the low performance drive. Remember, the outer edges of the platters are faster. If you have a 1TB drive, and split it into 2x500GB, you can fit A2 on the first partition and store all of your movies/music/documents/etc on the second.
By loading A2 into the outermost edge of the platter I was able to virtually eliminate FPS drop from hard drive activity. 1.04 still has a lag bug in cities, mind you, though that was fixed in beta a while ago and the game is quite fluid on my system now. Doing this also eliminates alot of visible texture loading on buildings when moving at high speeds.
I didn't use an FPS counter for testing, however the change after running Ultimate Defrag was immediately noticeable. I couldn't say for sure the difference, however I was frequently running up against texture pops and stuttering while moving at high speeds through the map.
I recently upgraded my memory from 2GB to 4GB (3.25GB addressable with 32-bit). There was a very noticeable change in performance with this upgrade after playing for more than an hour or so, moving about the map. If you only have 2GB, go ahead and upgrade it to 4GB. you won't be able to address it all, and A2 (according to specs and IIRC) won't address more than 2GB at a time, but you will get A) Dual channel performance increase and B) Full use of the allotted memory.
Also, when purchasing memory keep in mind that tighter timings will net better performance than "faster OMG mhz" memory with loose timings. I now run DDR800 with 4-4-4-12 timings, and the performance difference from my old memory is very considerable. The price difference is just about completely ridiculous, as my new high grade memory cost exactly $10 more than the equivalent "budget" memory that sports much looser memory timings. Having a good motherboard that supports manually changing memory timing is a MUST to make full use of this type of memory.
If your budget doesn't allow for an enthusiast motherboard right away, still get the better performance memory. You can always upgrade the motherboard later.
Done in moderation, overclocking your hardware can net some good performance gains without sacrificing hardware lifespan. When overclocking CPU, memory, etc. I use CPU Burn-in to stress the system. Start as many copies of this as you have processor cores, and run without error checking. If the system crashes, back off your overclock settings until it is rock solid for at least an hour at full steam. You MUST monitor your CPU temperature when attempting this. Failure to do so may result in a dead system! Be sure to check your idle CPU temperature in your BIOS before booting.
For overclocking video, I use furmark in "extreme burning mode". It will show what appears to be a static image, but really it renders the same image from scratch over and over. If you are pushing your overclock too hard, you will start to see graphical distortion, tearing, or areas of black rather like TV "snow". You can also monitor GPU temperature during the test and determine if your cooling solution is good enough. Moderately increasing your video card's clocks will definitely pay off with A2. Again, test for a good hour to ensure that you have a completely stable system.
If you choose this route, take it slow and easy. Change one setting or group of related settings at a time, and test, Test, TEST! Keep notes on the changes you make and revert to your last stable settings in case of a problem.
Ensure your system has adequate cooling. A2 is very demanding on all of your hardware. If you have any area inside your case that you can install a fan in and you do not have a fan there, install one. Thermally active and adjustable fans are preferable, as you can increase their airflow at need and decrease to reduce noise when you aren't stressing your system.
This is perhaps the most basic, but do ensure that your cooling surfaces and fans are clear of dust and debris. Do not neglect your video card.
Cooling and cleaning is often overlooked. Any intel CPU since the P4 will slow itself down when its core temperature rises. AMD CPUs do not have this feature. Inadequate cooling surfaces or fans that cannot move enough air will degrade performance and hardware life expectancy.
BIOS tweaks that may or may not help:
At this level, most tweaks will result in very little performance increase, though some options may reduce intermittent "stutter" or FPS drops. Disabling power saving features such as AMD Cool 'n Quiet, or Intel SpeedStep, may reduce intermittent lag when the CPU isn't used as much then suddenly has a load. A2 and A1 both have CPU usage profiles that fit this mark, and I would disable the power saving feature and test if it is causing the problem.
Enabling fast IRQ polling on XP:
WARNING - SEVERELY DANGEROUS.
I will not detail this procedure here, but only mention it. You may google the procedure at your own risk. With some registry editing, you can have XP poll IRQs faster than the kernel normally would. This increases responsiveness especially to controls, and even more especially if you use a huge pile of USB devices. Incorrectly editing this feature can damage your operating system beyond repair.
Alternative to fast IRQ polling on any windows OS:
If your USB controls aren't as responsive as you would like, ensure that you install your controls (usually keyboard/mouse) directly into the computer. Do not use a USB hub for them. USB is a shared pipe, so the more USB devices you have on each controller set, the slower the connection. High end controls won't help if it must work with 1/2 or 1/3 or even 1/4 of the bus speed. The speed is affected even if the other connected devices are not in use.
On most motherboards, the controllers are setup on each pair. So if you have a keyboard and mouse, use both ports for these. If you have the space, only plug one USB device in each set of two. Since USB2.0 came out, the problem is lessened, but it can still increase latency and cause you to wreck or shoot high/low or anything else that matters.
USB hubs are best purposed for mostly unused devices where the speed doesn't matter as much, like card readers, ipods, etc.