What Are L1 and L2 Cache and Bus Speeds?


There are still more PC parts that will make a real difference in how responsive your computer feels.

Luckily, since you are buying – not building – a PC, you don’t need to know much about them.

This is Part 4 in the How To Buy A New Computer Series

There is a special type of computer memory known as “cache.” Bits and pieces of frequently used data are cached for speedy recall. When you dig into a new PC’s specs, you may see something like:

Intel® Core™ 2 Quad Q9550 (2.83GHz, 12M L2Cache, 1333FSB)

We know what Core2 Quad means; Q9550 is the processor model number. 2.83 GHz is processor speed. But what are L1 and L2 cache and 1333FSB?

L1 cache is usually integrated into the CPU – it is a way for the CPU to grab stored data very quickly. L2 cache is usually a special chip on the motherboard. Again, it is specialized memory that data can be sent to and retrieved from with extreme speed. All you, as a PC buyer, need to know is a larger number means faster performance.

FSB is the abbreviation for Front Side Bus. It is the highway that data travels along as it moves from CPU to RAM and other parts of your PC. Again – you need only know that higher numbers are faster.

When you shop for a PC from a major manufacturer, it is unlikely that you will be able to independently choose cache or bus speeds.

But here’s the thing worth knowing: cheaper computers will have slower L2 cache and FSB speeds. Since these are arcane parts, most consumers will never hear about them. But they are a major reason why two seemingly similar PCs can be priced so differently.

A 2.83 GHz processor may be set into a motherboard with older cheaper L2 cache and the data transfer may be strangled by an inadequate bus. Although the advertisement for the computer will prominently feature the processor speed – and the low, low price – you will not get an adequate picture of the computer’s real speed. When you plug it in and start working, your brand new computer may feel sluggish.


When two computers have similar CPU and RAM, but very different prices, compare the specs more closely before plunking down your money. This may not be a case of the “generic” brand costing less. It’s more likely to be a Rolls Royce grill slapped on a Volkswagen.