What is a wait state in computing?
The time spent waiting for an operation to take place. Wait states are often idle computer cycles, because a computer’s CPU is much faster than main memory.
How long is a wait state?
A wait state is nothing more than an extra clock cycle to give some device time to complete an operation. For example, a 50 MHz 80486 system has a 20 ns clock period. This implies that you need 20 ns memory.
Why wait state is needed?
Wait states can be used to reduce the energy consumption of a processor, by allowing the main processor clock to either slow down or temporarily pause during the wait state if the CPU has no other work to do.
What type of high-speed RAM does the CPU use to reduce wait states?
static RAM (SRAM)
Can CPU read assembly?
A CPU doesn’t actually understand assembly language. Assembly language is the human-readable expression of machine language, which is just patterns of bits (binary digits). A CPU can deal only with machine language.
How many caches do modern CPUs usually have?
Most modern CPUs have at least three independent caches: an instruction cache to speed up executable instruction fetch, a data cache to speed up data fetch and store, and a Translation Lookaside Buffer (TLB) used to speed up virtual-to-physical address translation for both executable instructions and data.
Is 12mb cache good?
12mb L2 cache is misleading because each physical processor can only see 4mb of it each. i7/i5 is more efficient because even though there is only 256k L2 dedicated per core, there is 8mb shared L3 cache between all the cores so when cores are inactive, the ones being used can make use of 8mb of cache.
Why is L1 cache faster than L2?
Intel uses an L1 cache with a latency of 3 cycles. The L2 cache is shared between one or more L1 caches and is often much, much larger. Whereas the L1 cache is designed to maximize the hit rate, the L2 cache is designed to minimize the miss penalty (the delay incurred when an L1 miss happens).
Is L1 faster than L2?
CPUs often have a data cache, an instruction cache (for code), and a unified cache (for anything). Accessing these caches are much faster than accessing the RAM: Typically, the L1 cache is about 100 times faster than the RAM for data access, and the L2 cache is 25 times faster than RAM for data access.
What is the purpose of L2 cache?
The level 2 cache serves as the bridge for the process and memory performance gap. Its main goal is to provide the necessary stored information to the processor without any interruptions or any delays or wait-states.
Is more L1 cache better?
L1 hit-rate is still very important, so L1 caches are not as small / simple / fast as they could be, because that would reduce hit rates. Achieving the same overall performance would thus require higher levels of cache to be faster.
Why is L1 cache so small?
L1 caches are small for a reason. It takes less time to decode the index and control signals to the cache. It takes less time to search the cache tags to figure out whether there is a cache hit. It takes less time to multiplex the result of the right cells out towards the output and to the ALU’s that use them.
Why is L1 cache expensive?
L1 is closer to the processor, and is accessed on every memory access so its accesses are very frequent. Thus, it needs to return the data really fast (usually within on clock cycle). It also needs lots of read/write ports and high access bandwidth. Building a large cache with these properties is impossible.