Ming’s Wisdom

The comparative speed of different components in a computer system is often a source of confusion. For example, a programmer could attempt to optimize their program by reducing the number of processor cycles needed to get something done, in exchange for needing one extra hard drive access, thinking that reducing their loop to one-tenth of its original size would surely provide more speed benefit than the hard drive access takes away.

To put things in perspective, I’ve assigned a number to each process available in a computer, to show their relative speed. (If something has a number of 13, that means in the time it can be performed once, something else with number 1 can be performed 13 times).

• 1                                                             processor instruction (1/3 billionth of a second)
• 2                                                             cache access
• 30                                                           memory access
• 75,000                                                   solid state drive          (1/40,000th of a second (1) )
• 36,000,000                                           hard drive access      (1/100th of a second)
• 480,000,000                                         dvd drive access
• 50,000,000 to 1,500,000,000            internet access          (1/3rd of a second (2) )

This should really put things into perspective. A billion instructions worth of program can be executed before the first communication can be established with another computer on the internet across the globe. Of course, these are just rough numbers representing times to first access, but it should give you an idea how vast these differences are.

What this means for non-programmers is several things (these astounding numbers are the reason behind these common suggestions):

1. if you backup all your pictures and documents to a hard drive or solid state drive, you’ll be able to access it much faster than if you make DVDs or use a backup website.
2. copying commonly used items from cd onto a hard drive will make them open much faster
3. if your computer feels like it’s slow, and you hear lots of hard drive access noises, buy more memory so that programs don’t need to resort to saving overflow from memory to hard disk.
4. if you often work with games or Photoshop, or other programs that might need to access lots of files often, then a solid state drive could make your life a lot easier.

What this means for programmers is that, in the vast majority of programs, being even a little smart about not accessing drive storage or the internet can have more speed benefit than even the most clever hacks to speed up other program code. For example, instead of asking for the same information twice from the internet, save it to memory to re-use later, it will speed up a small portion of your program by at least one hundred million percent .

Notes:

1) solid state drives are much faster at getting to files than hard drives, but sustained copying speed is similar.

2) internet access speeds vary depending on distance to the remote computer, and the quality of the link between the two computers. in general, you never know how long it will take.

This entry was posted on Sunday, August 16th, 2009 at 20:04 and is filed under Technology. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.