What is CPU Cache?

When you think of memory in your computer you might think of DDR modules, VRAM on your graphics card or more likely the hard drives and the SSD’s.  Actually there is another type of memory that is incredibly fast and essential to the speed we got accustomed to modern computers. I’m talking about your CPU cache memory.

It’s a specialized type of memory built into your CPU, but why the heck would the processor need its own memory? Well your RAM is heck lot faster than your hard drive but your CPU actually needs few data even faster than your RAM can even provide it. On top of that our CPU’s have got faster over the year and continue to outstrip typical RAM module by wider margins. Meaning without cache memory your CPU would be sitting and doing nothing like an unproductive employee and your RAM becomes a bottleneck. It is where cache comes in. Unlike your RAM which is actually DRAM (Dynamic RAM) your CPU cache is SRAM (Static RAM) which is more expensive but it’s much faster than DRAM because it need not be completely refreshed in order to hold data which the DRAM has to do. An average CPU would have few megabytes of cache but it makes tremendous use of this small amount of memory.

You see when a CPU accesses something from your main system RAM it generally stores in its cache, then uses complex algorithm to guess as to what other instruction and data it might need next and it fetches that from your system RAM as well. Since these guesses aren’t perfect CPU suffers from something called “Cache Misses” where it searches its own cache and cannot find what it needs and has to search system memory directly instead, which slows things down. Fortunately modern processors have gotten pretty good in deciding what to put inside caches as they typically have cache hit rate better than 80 percent meaning that most of the time CPU is only processing what it finds in cache and doesn’t has to bother talking to your slow system memory. As you guess more cache is advantageous so do check you CPU’s spec sheet before buying new CPU. Okay, now the question comes that will more cache give me better fps in games or tremendous speed in other stuff? Well this can depend on the specific application but you can’t see performance increase overall on CPU’s with larger caches. Fortunately though if you are buying a higher end processor as you need more cores or better over clocking potential then it will probably come with more cache as well. Off course if you really want that high end silicon cache then make sure that how much you are paying in cash.

Also check out Difference between DDR, DDR2, DDR3 and DDR4 RAM.

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