Steam game download/installing issue

[Man]

So I don't have the best hard drive, but I have good 1 Gbit internet speed, and my problem is that Steam is downloading the games at 90-100 MB/s, but because it's installing it while it's downloading it, I start downloading the game for like 5 seconds at a high rate, then it goes to zero. Then rinse and repeat. I want to know if there is a way to have the download and installation process separate, meaning Steam first downloads the game and then installs it, because it would be a lot faster than the current process.

[Cathulhu]

Sounds like your PC can download fast, but fails to process the data in a timely manner.
Which is usually down to either the CPU or the harddrive not being up to the task, or some software interfering with processing the data.

[Man]

Right, I'm pretty sure it's my hard drive, but is there no way to set up Steam so that it does it in 2 separate processes instead of one?