When was l3 cache introduced

What on Earth does way set associative even mean? But of course, there's much more we can learn about cache Let's begin with an imaginary, magical storage system: it's infinitely fast, can handle an infinite number of data transactions at once, and always keeps data safe and secure.

Not that anything even remotely to this exists, but if it did, processor design would be much simpler. CPUs would only need to have logic units for adding, multiplying, etc. This is because our theoretical storage system can instantly send and receive all the numbers required; none of the logic units would be held up waiting for a data transaction.

But, as we all know, there isn't any magic storage technology. Instead, we have hard or solid state drives, and even the best of these aren't even remotely capable of handling all the data transfers required for a typical CPU.

The reason why is that modern CPUs are incredibly fast -- they take just one clock cycle to add two 64 bit integer values together, and for a CPU running at 4 GHz, this would be just 0.

Meanwhile, spinning hard drives take thousands of nanoseconds just to find data on the discs inside, let alone transfer it, and solid state drives still take tens or hundreds of nanoseconds. Such drives obviously can't be built into processors, so that means there will be a physical separation between the two.

This just adds more time onto the moving of data, making things even worse. So what we need is another data storage system, that sits in between the processor and the main storage. It needs to be faster than a drive, be able to handle lots of data transfers simultaneously, and be a lot closer to the processor. Well, we already do have such a thing, and it's called RAM , and every computer system has some for this very purpose.

Almost of all this kind of storage is DRAM dynamic random access memory and it's capable of passing data around much faster than any drive. So although we've improved the speed of our data network, additional systems -- hardware and software -- will be required in order to work out what data should be kept in the limited amount of DRAM, ready for the CPU.

CPUs are pretty small, though, so you can't stick that much into them. The vast majority of DRAM is located right next to the processor, plugged into the motherboard, and it's always the closest component to the CPU, in a computer system. And yet, it's still not fast enough DRAM still takes around nanoseconds to find data, but at least it can transfer billions of bits every second. Looks like we'll need another stage of memory, to go in-between the processor's units and the DRAM.

Enter stage left: SRAM static random access memory. Where DRAM uses microscopic capacitors to store data in the form of electrical charge, SRAM uses transistors to do the same thing and these can work almost as fast as the logic units in a processor roughly 10 times faster than DRAM.

But since it's made through same process as creating a CPU, SRAM can be built right inside the processor, as close to the logic units as possible.

With each extra stage, we've increased the speed of moving data about, to the cost of how much we can store. We could carry on adding in more sections, with each one being quicker but smaller.

And so we arrive at a more technical definition of what cache is: It's multiple blocks of SRAM, all located inside the processor; they're used to ensure that the logic units are kept as busy as possible, by sending and storing data at super fast speeds. Happy with that? Good -- because it's going to get a lot more complicated from here on! As we discussed, cache is needed because there isn't a magical storage system that can keep up with the data demands of the logic units in a processor.

Modern CPUs and graphics processors contain a number of SRAM blocks, that are internally organized into a hierarchy -- a sequence of caches that are ordered as follows:.

In the above image, the CPU is represented by the black dashed rectangle. The ALUs arithmetic logic units are at the far left; these are the structures that power the processor, handling the math the chip does. While its technically not cache, the nearest level of memory to the ALUs are the registers they're grouped together into a register file. Each one of these holds a single number, such as a bit integer; the value itself might be a piece of data about something, a code for a specific instruction, or the memory address of some other data.

The register file in a desktop CPU is quite small -- for example, in Intel's Core iK , there are two banks of them in each core, and the one for integers contains just bit registers.

The other register file, for vectors small arrays of numbers , has bit entries. So the total register file for each core is a little under 7 kB. But they're not designed to hold very much data just a single piece of it , which is why there's always some larger blocks of memory nearby: this is the Level 1 cache.

What happens now in the program is the CPU needs to find out what this variable [tomweapon] actually means. As before with [tomweapon], at this point the CPU now needs to know what this variable [tomweapondamage] stands for, so it takes the long trip over to the Spectrums memory and finds [tomweapondamage] and the value of [5].

And in most cases this was fine. CPUs were dog-slow, and with memory which was also dog-slow, it was a good match. But CPU speeds started to improve quickly while memory speeds improved much more slowly. Of course there was a simple solution. If those trips out to memory are taking too long, then we need to shorten the trip. Here we can see a die shot with the memory cache, which looks like 4 blocks of 2KB of cache, for a total of 8KB of cache memory.

Well the thing about this new memory cache on the CPU was that even though it was a lot smaller , it was much, much faster than system RAM. So the trick was to ensure only the most frequently used data was stored on the cache.

Remember that on line 70 we had to take a trip out to memory to find the value stored in [tomweapondamage], only to have to do it again on line With a CPU cache, the first time any data is accessed from the main memory a copy of it is stored in the cache.

So all these variables. Now the next time the CPU needs the information in [tomweapondamage] which in our case is the very next line of code , it looks in the CPU cache first, finds it and completes the line of code in a fraction of the time it would have taken had it needed to go all the way out to system memory again. And every subsequent time the computer needed that information, it was usually right nearby in the cache. Computer software is actually quite predictable — even games.

So the benefits of having fast memory on the CPU was clear, and cache sizes began to increase as more and more of the CPU area was given over to it. But increasing the size of the L1 cache also increased the average latency — as it had to go through more and more memory to find the desired data — so it soon became a tradeoff between size and speed.

The answer to this growing problem was to add a second level of cache — L2 cache. The instruction cache holds the most frequently used programming instructions while the data cache holds the most frequently used data.

The L2 cache was allowed to grow a bit larger, which again meant it was slower than L1 — however still much, much faster than going out to the main memory. L2 caches hold both instructions and data and are often inclusive of L1 — that is all the blocks held in L1 are also held in L2.

CPU caches are actually divided into blocks where each instruction or piece of data is stored. Now imagine over the course of the game, the L1 cache starts to fill up with the most frequently used data.

Our main character Bob maybe found some armour which reduces all the damage he takes and perhaps he also learned how to cast spells so he now has [bobmanapoints] as well as [bobhitpoints]. This is all very important data which will be frequently used by the program.

As before, when the program first tries to use this data, a read request is sent to the memory controller which first of all looks in the L1, then the L2 caches before finding it in main memory.

And whenever the data is read from the L2, a copy is placed in L1, which will mean that something else will have to be evicted from the L1 cache by the exact same mechanism described above. Just as L2 is larger and slower than L1, the L3 is larger and slower than L2, but still quite a bit faster than system memory. It was actually a re-purposed server CPU as Intel had to go to unprecedented lengths in order to remain somewhat competitive. Soon we had quad cores and L3 caches became larger and larger over time, as chip architects tried to push the trip to system memory further and further away.

Looking at an individual CCX, we see 4 cores, with a large shared 8MB L3 cache in the middle with two cores either side. Remember this is one core complex and Zen has two of these per chip so in total the chip would have 16MB of L3 cache. Just to the right of the core in this example is KB of L2 cache, again as part of the core.

Gorilla Glass is an alkali-aluminosilicate glass developed by Corning that's primarily used as cover glass for mobile devices. Because it's resilient, durable and remarkably thin, it has been made to safeguard displays and touch screens without compromising the screen or adding bulkiness to the View Full Term. By clicking sign up, you agree to receive emails from Techopedia and agree to our Terms of Use and Privacy Policy. A Level 3 L3 cache is a specialized cache that that is used by the CPU and is usually built onto the motherboard and, in certain special processors, within the CPU module itself.

It works together with the L1 and L2 cache to improve computer performance by preventing bottlenecks due to the fetch and execute cycle taking too long. The L3 cache feeds information to the L2 cache, which then forwards information to the L1 cache.

Typically, its memory performance is slower compared to L2 cache, but is still faster than the main memory RAM. The L3 cache is usually built onto the motherboard between the main memory RAM and the L1 and L2 caches of the processor module. This serves as another bridge to park information like processor commands and frequently used data in order to prevent bottlenecks resulting from the fetching of these data from the main memory.