TonyACG51
I studied computers and know a lot about the hardware and bottlenecking issues. Here's a LONG reply that I hope you find informative:
You appear to have some misconceptions about the way computers work. This whole DVD-thing is a non-issue. There is absolutely no direct relationship between your hard drive and DVD drive. They are two different ways of storing data. Your computer reads the DVD and copies the data to the hard drive because the hard drive is faster to access but there's nothing the game needs on that disc once this is done except the verification file used to help prevent piracy (which can be bypassed by a NOCD crack which I don't object to provided you own the game but it's probably technically illegal.)
XBOX:
What you are talking about reminds me of game consoles like the XBox where they did read from a disc which made things really slow. The discs also became scratched and unreadable in many cases.
I'm unsure whether you can fully install all games to modern XBox and PS3 machines. I suspect that the next generation of consoles may use ONLY downloadable games due to piracy. They may have a DVD drive but it's possible this will be for movies only.
Bottlenecks:
There are several bottlenecks in any computer. Here's how it works:
1) Motherboard BIOS:
When you cold start or start from Hibernation, your motherboard will run a series of tests to verify things are working. This usually takes about 20 seconds. There is a quick test and a longer test. The longer test verifies more of your System RAM (i.e. DDR3 RAM) but not all of it. When you recover from Standby your system is already partially on and your RAM still contains Windows so there's no BIOS startup; in Standby you're waiting for your screen so start or your hard drive to spin up but it's a matter of a few seconds.
2) Hard drive/SSD:
Windows initially loads from your hard drive into your System RAM (i.e. your 4GB of DDR3). When you start a program like Microsoft Word, it loads and runs from your System RAM. If you don't have enough RAM, Windows is force to remove programs from RAM so when you use them again it must access the hard drive. The optimal amount is 4GB even for gamers. 8GB is a waste for all but people with specific needs for editing massive media files using programs like Photoshop. It adds heat and probably will slow things down a little (it's best to buy 4GB of DDR3 with lower timings than 8GB of RAM). Very few people need more. With Windows 7, a casual business user could get by nicely with 2GB.
Games intially load from your hard drive and may need to load new levels or areas from the hard drive. A well designed game pre-buffers the next area into your RAM of a map so you aren't suddenly frozen waiting for the next area to load.
3) System RAM (i.e. 4GB DDR3):
RAM is rarely a bottleneck in most systems. There's two potential types of RAM bottlenecks. One is having not enough (then the bottleneck is really your hard drive), and the other is not being FAST enough to keep up with your CPU.
For example, if your CPU is running a game, that game is stored in RAM. It keeps stepping through the program instructions in that RAM. If your RAM was too slow then the CPU can't be used to its full potential because it's waiting (like an assembly line).
System RAM is rarely a bottleneck any more. You typically need a high-end CPU running at close to 100% to have problems (and even then your RAM may be keeping up). Note that if your CPU is running at 100% then your RAM can NOT be the slowing it down because obviously it's sending it the data fast enough. For gaming, I wouldn't expect to see RAM issues unless you had something like an i7-920 overclocked to keep up with your Crossfire HD5870 setup.
4) Graphics card:
Your graphics card is often the slow part in actual game play. An i5-750, i7-860/920 CPU averages about 50% usage for moder games (usually varies between 20 and 60%). Overclocking is difficult without a massive heatsink or water cooling; a 2% increase in a normal card is not really worth the extra instability and decreased lifespan. Anyway, your CPU sends the graphics card information for it to crunch and often the graphics card runs at 100% thus the CPU is waiting to send it data. Usually the only time your graphics card is NOT a bottleneck is if you're using VSYNC. If the game can run at 90FPS (faster than your monitor can display), you should have VSYNC enabled so it runs at your displays typical 60FPS (60Hz). Not only will the graphics card run quieter, you will also avoid screen tearing (Google "tearing vsync" if you don't understand).
Bottleneck summary:
There are several types of bottlenecks which occur at different times. For games, the loading of it initially and for new levels is the hard drive. RAM is rarely a bottleneck. The CPU is typically only a bottneck for older systems with a newer graphics card which the CPU can't keep up with (very common situation). The graphics card is frequently the main bottleck for gamers.
You can easily monitor your CPU using with the Task Manager (CTRL-ALT-DEL)-TM->"Performance". Change "View->Update Speed" to "LOW." Note that if you have Hyperthreading enabled the CPU results will be incorrect (will read too low); this is because Windows treats the Hyperthread as if it were an actual CPU core but in reality the most it could add would be an extra 30% (If all four cores and all four threads showed 100% you'd be processing 30% faster than if only your four cores were enabled with Hyperthreading OFF). In fact, because very few programs can use all your cores, hyperthreading can cause a slow-down when a game or application chooses a thread over a core. Unless you have at least one core maxed out at 100% it's not even worth checking out but if you're stressing your CPU you should benchmark your game or application with and without hyperthreading enabled (enabled via the BIOS). This is why the i5-750 is such a great deal. Very few people ever need hyperthreading but it's $100 less than the i7-860 which is otherwise about the same. I leave it enabled because I used Task Manager to confirm my CPU was never close to 100% for any game I own.
Recommendations:
High-end on a budget: i5-750, 4GB DDR3 1600MHz, HD5850 1GB
Long-run gaming information:
Once the next-generation of the XBox comes out (2012?), PC gaming will take a sharp dip and eventually be phased out for high-end gaming. While you can theoretically always be ahead of a game console by purchasing the latest PC hardware the game consoles are quickly approaching "good enough." There's also a huge cost for the consumer and the developer on the PC. Developing for a single, known hardware setup is significantly cheaper for development and troubleshooting after the fact. Another huge issue is the constant stream of problems with software and hardware which just never ends. (Also game consoles are smaller and quieter than an equivalently performing PC. Look at the new PS3 slim).
I'll never purchase another PC gaming system.
The future of gaming:
1) game consoles
2) streaming (processing is server-side thus minimal hardware setup which will be included in most future HDTV's)
3) PC (high-end machines will disappear in favour of low-cost/efficient machines. The lack of hardware and cost of game development will prevent high-end games though a niche will remain for more casual gaming. Streaming will eventually work fairly well though, allowing high performance games to run on a PC since these are processed by the server.)