Thread: Intel's L1 & L2 &L3 Cache

I know that Cpu cache is very useful, Its the first thing that cpu search's before ram, and runs much faster than ram, and closer to the cpu to keep away from latency.

What i want to know is what do they mean by L1 Cache L2 Cache and L3 Cache, and what’s the differentiation between them.

Also, what’s the cause of making smaller CPU's every 2 or 3 years, for example, Pentium Dual-Core used a 65nm, core i7 uses 45nm, what’s the difference between them other than one is smaller than the other, and what benefits do they get?

Thanks in advance.

L1 cache is the smallest and fastest. L2 is slower and larger; L3 is yet slower and larger. Also, in current designs, each core gets its own dedicated L1 and L2, but L3 is shared between all the cores.

As for the size? The CPUs aren't shrinking. In many cases, they're growing. The size you refer to is the size of an individual transistor within the CPU. The smaller each transistor is, the more of them will fit in your CPU, allowing for faster CPUs with more stuff crammed in. Smaller transistors also switch faster, allowing higher clock speeds, and use less power.

Thanks for reply
It means;

L1 Cache is the fastest Cache, each core has its own L1 cache it’s the smallest but it’s the fastest and the first one to accesses by the Core.

L2 Cache is slower than L1; L2 cache is the 2nd cache that the core search's for its data, and bigger than L1.

L3 Cache is shard between all of the cores, in the core i7 for example, is shared between all 4 cores, and bigger than both L1 and L2.

so basically what your saying is, Cpu first search's L1 cache, if a miss happens, then it goes to the bigger cache which is L2, if it don't find the data that is looking for there, then it goes to the bigger Cache which is L3 Which is Shared between all 4 cores.

So is L1 Cache faster because its smaller than l2 and l3 or is it faster because its the first cache the cpu looks into?


So 65 and 45 is inside of the CPU chip? i thought it was something else.

So the smaller it gets the better clock speed we get and the less power, ok i got that one.

Please correct me if my info isn’t right.

L1 faster because it is smaller and because of its proximity to the CPU core. The design of the cache is also different. L3 is also on a separate power and clock plane to the CPU cores - L1 and L2 run at the CPU clock speed, but L3 runs at a slower clock.

As for the 65 and 45, yes, those are the size of the elements inside of the chip itself. Here's a good way to show it:

The Pentium 4 "Northwood" chip had a die size of around 145 mm^2 (the physical size of the chip) with 55 million transistors at 130 nm.

The current i7 "Bloomfield" chip has a die size of 263 mm^2. It also contains 731 million transistors at 45nm. This means that a Bloomfield i7 is around 1.8 times larger than a Northwood Pentium 4, but contains 13.3 times the number of transistors. This is what the smaller number means - Bloomfield can pack 13.3 times the number of transistors into just 1.8 times the area with around double the power consumption. This allows for a far more complex and high performance chip without too much of an increase in power or size.