Choose 533 or 667? Detailed description of the relationship between CPU and memory

Choose 533 or 667? Detailed description of the relationship between CPU and memory
 

I recently read some questions from some netizens about CPU, such as the gap between front-end bus 533 and 667, and how about the memory of ddrii667 on t2050 (Front-End bus 533 MHz ?...... I want to write thisArticleSo that more friends can understand this layer-by-layer relationship and know how to choose CPU and memory!

We know that computers have many accessories, and the speed varies with accessories. In 286, 386, and early 486 computers, the CPU speed is not too high, and the memory speed is the same. Later, as the CPU speed increases rapidly, the memory cannot be increased as high as the CPU speed due to the electrical structure (even if the current memory reaches 400, 533, but compared with the speed of several G of the CPU, it is not a level at all), resulting in a speed difference between the memory and the CPU, in this case, the concept of CPU clock speed, frequency doubling, and external frequency is proposed. The external frequency is the external frequency of the CPU, that is, the memory frequency. The CPU uses this frequency to contact the memory. The CPU clock speed is the actual operation speed inside the CPU. The clock speed must be a factor higher than the external frequency, which is a multiplier. For example, you have picked up an Intel 486 CPU from the computer garbage collection, with 486 dx/2 66 printed on it. The 486 CPU clock speed is 66 MHz, and dx/2 represents a 2-frequency doubling. Therefore, the outbound CPU frequency is 33mz, that is, the memory operating frequency, this is also the frequency of the front-end bus FSB. Because the CPU is connected to the memory through the front-end bus, the memory operating frequency (or the external frequency is also good) is the front-end bus frequency. The front-end bus frequency is 33mz for the 486 CPU in the garbage dump just now. Such a front-end bus structure continues until 486 after the Pentium (as the saying goes, 586), Pentium 2, Pentium 3, such as a 3 133 MHz CPU, external frequency, that is to say, its front-end bus is 133 MHz, and the memory operating frequency is also 133.

in the 4 s of Pentium, the working modes of memory and CPU have changed, and the concept of Front-End bus has become somewhat complicated. The Pentium 4 CPU uses quad pumped (4 times of concurrency) technology, which enables the system bus to transmit four times of data in a clock cycle, that is, the transmission efficiency is four times the original, it is equivalent to using four original front-end buses to connect to the memory. When the external frequency is still 133 MHz, the speed of the front-end bus is increased by 4 times to 533x4 = 200 MHz. When the external frequency is increased to 800 MHz, the front-end bus is changed to MHz, so you will see p4 of the 533 Front-End bus and P4 Of the 800 Front-End bus. Their actual external frequency is only 133 and 200, but because people keep the old concept that the Front-End bus is the external frequency, they are used to the so-called 533 external frequency P4 and 800 external frequency P4. In fact, it is more appropriate to call the 533 Front-End bus or the 533 FSB P4.

What about the memory? If the outer frequency is not completely equal to the front-end bus, is the outer frequency equal to the memory frequency? The memory has evolved to DDR. Compared with the original one, the data in a clock cycle can be transferred twice as much as the original one. DDR stands for double data rate, meaning double data transmission rate. The DDR transmission speed is 266 at the 133mhz external frequency. When the external frequency is increased to 400 MHz, the DDR transmission speed is. This means ddr266 memory and ddr400 memory.

Let's take a look at the relationship between the current external frequency, memory frequency, and CPU Front-End bus. In the past P3, the external frequency of 133, the memory frequency is 133, and the front-end bus of the CPU is also 133. The three are the same thing. At present, the P4 CPU reaches 133 MHz with a 533 outbound frequency, and the memory frequency is 266 (ddr266 ). When the problem arises, the front-end bus is a bridge between the CPU and the memory. At this time, the front-end bus reaches 533, while the memory is only 266 faster, and the memory is half slower than the front-end bus of the CPU, theoretically, the CPU has to wait for the memory to transmit data before processing the data. This means that the memory is dragging the CPU down. This is indeed the case. This is true for 845 and 848 boards. Therefore, the concept of a dual-channel memory is proposed. The two memory uses two channels to work together to provide data, which doubles the speed again. The two ddr266 have a speed of 266x2 = 533, it's exactly the front-end bus speed of the P4 CPU. When the external frequency is increased to 200, the CPU Front-End bus is changed to 800. Two ddr400 memories constitute a dual channel, and the memory transmission speed is also 800. Therefore, to make good use of P4, you must use dual-channel memory (of course, this is the case before the emergence of ddrii), more than 865 of the motherboard provides this function. However, the 845 and 848 boards do not have a dual-channel memory function.

What I just talked about is Intel P4's FSB concept. Its rival AMD's CPU is different.

The old 462-pin amd cpu adopts the ev6 Front-End bus, which is twice the outer frequency. That is, when the 133 outer frequency is used, the fsb of the amd 462-pin CPU is 266, it's just right to use ddr266 memory with him. If two ddr266 is used as a dual-channel, although the memory has a transmission speed of 533, it has little effect on 266 FSB, therefore, the dual-channel memory does not significantly help the CPU.

The new AMD 754/939 64-bit CPU is integrated with the Memory Manager (previously the memory manager is in the motherboard). Therefore, the FSB frequency of the amd 64-bit CPU Front-End bus is consistent with the actual CPU frequency.

That is, the frontend bus means that 800 of the u is used on the 533 board, and the U is reduced to 533. ddr400 is only the speed of ddr266.
The front-end bus (FSB) frequency (that is, the bus frequency) directly affects the direct data exchange speed between the CPU and memory.
CPU clock speed = bus frequency * Multiplier

The difference between the external frequency and the FSB frequency: the speed of the front-end bus refers to the speed of data transmission, and the external frequency is the speed of synchronous operation between the CPU and the motherboard.

Therefore, FSB is the 533 main version!

FSB is speed. Depends on the bus frequency.

FSB (Front-End bus) Front side bus
Within a PC, one device and the other transmit digital signals through the system bus. The CPU can communicate with memory, video card, and other devices through the front-end bus (FSB. The faster the FSB frequency, the more data the processor obtains per unit of time, and the higher the processor utilization.
The front-end bus frequency directly affects the speed of direct data exchange between the CPU and memory. Because of its special technology, it exists in the CPU and memory (the CPU exchanges data with the memory through the North Bridge Memory Manager) the bus can complete two or even four transmission times in a clock cycle, which is equivalent to several times more than the frequency. (That is, the number of times the external CPU frequency .)

Intel and AMD use different technologies on FSB.
Intel FSB frequency = CPU external frequency * 4
For example, 2.4c external frequency 200 MHz, FSB frequency 800 MHz
Amd fsb frequency = CPU external frequency * 2
For example, the athlon XP 2500 + (Barton) External frequency is 166 MHz, and the FSB frequency is 333 MHz.

FSB bandwidth indicates the data transmission speed of FSB, in MB/s or GB/s.
FSB bandwidth = FSB frequency * FSB Bit Width/8. Currently, the FSB bit width is 64 bits.
For example, P4 2.0a: FSB bandwidth = 400 MHz * 64bit/8 = 3.2 Gb/s.

I believe you should have understood these concepts through a large string of text descriptions above. ^_^ I will take my notebook as an example to give you a more vivid and clear explanation. My current version is HP v3172tu, the CPU is core t2050 (Front-End bus 533), and the memory is hy ddrii667. If my memory is ddrii533, It is synchronized with the front-end bus of the CPU, the memory transmission speed has just reached its limit. While my memory is ddrii667, but because the t2050 CPU Front-End bus is 533, the actual memory can only work at a 266mhz frequency, less than 333mhz frequency, therefore, the memory performance is not fully realized. If I replace the t2500 CPU and the front-end bus reaches 667 MHz, the memory of this ddrii667 will be able to run at full speed at MHz to maximize its performance. In this case, my friends should have fully understood it. ^_^

 

We can see that the actual working frequency of my ddrii 667 memory is 266 MHz, that is, the standard frequency of ddrii 533.

What's the gap between 533 and 667? According to the test, the difference between ddrii 533 and 667 with the same CPU usage is between 5% and 10%. This gap is very large, because the performance improvement brought about by the dual-channel is about 5%.

I hope these things will help you! Pai_^

 

 

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