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For example, a system with an external clock of 100 MHz and a 36x clock multiplier will have an internal CPU clock of 3.6 GHz. The external address and data buses of the CPU (often collectively termed front side bus (FSB) in PC contexts) also use the external clock as a fundamental timing base; however, they could also employ a (small) multiple ...
Address and control signals are still sent to the DRAM once per clock cycle (to be precise, on the rising edge of the clock), and timing parameters such as CAS latency are specified in clock cycles. Some less common DRAM interfaces, notably LPDDR2 , GDDR5 and XDR DRAM , send commands and addresses using double data rate.
Without knowing the clock frequency it is impossible to state if one set of timings is "faster" than another. For example, DDR3-2000 memory has a 1000 MHz clock frequency, which yields a 1 ns clock cycle. With this 1 ns clock, a CAS latency of 7 gives an absolute CAS latency of 7 ns. Faster DDR3-2666 memory (with a 1333 MHz clock, or 0.75 ns ...
Further, a "cumulative clock rate" measure is sometimes assumed by taking the total cores and multiplying by the total clock rate (e.g. a dual-core 2.8 GHz processor running at a cumulative 5.6 GHz). There are many other factors to consider when comparing the performance of CPUs, like the width of the CPU's data bus , the latency of the memory ...
In digital electronic design a clock domain crossing (CDC), or simply clock crossing, is the traversal of a signal in a synchronous digital circuit from one clock domain into another. If a signal does not assert long enough and is not registered, it may appear asynchronous on the incoming clock boundary.
This type of clock gating is race-condition-free and is preferred for FPGA designs. For FPGAs, every D-type flip-flop has an additional CE input signal. Clock gating works by taking the enable conditions attached to registers, and uses them to gate the clocks. A design must contain these enable conditions in order to use and benefit from clock ...
The Time Stamp Counter was once a high-resolution, low-overhead way for a program to get CPU timing information. With the advent of multi-core/hyper-threaded CPUs, systems with multiple CPUs, and hibernating operating systems, the TSC cannot be relied upon to provide accurate results — unless great care is taken to correct the possible flaws: rate of tick and whether all cores (processors ...
When a program wants to time its own operation, it can use a function like the POSIX clock() function, which returns the CPU time used by the program. POSIX allows this clock to start at an arbitrary value, so to measure elapsed time, a program calls clock(), does some work, then calls clock() again. [1] The difference is the time needed to do ...