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2024年8月29日发(作者：仪平彤)

内存频率（Memory frequency）

Memory frequency tangled, memory frequency why chaos

(computer reported D 2008 Thirteenth Edition) the teacher will

say why frequency tangled? The main reason is that people often

use memory frequency, particle frequency, and equivalent

frequency in conversation. How can the new computer friends

hear the frequency of so many versions? Today the teacher and

classmates Kiki to understand these frequencies.

Lay the foundation for understanding first

1. what is the memory frequency?

Our usual DDR2 800, DDR2 667, followed by 800, and 667, is the

memory frequency value. The memory frequency is usually

measured in MHz (megahertz), and the memory frequency

determines the actual memory performance to a certain extent.

The higher the memory frequency, the faster the memory is under

normal operation. For example, DDR2 800 means that the memory

bar has a frequency of 800MHz, which is better than the other

DDR2 667 (frequency 667MHz) in the case of other parameters.

Tip: we introduced the meaning of delay in the previous period.

As long as the memory delay values are very small, such as 5

and 6, they have very little effect on memory performance. On

the other hand, if the memory delay value is too large, then

the performance impact on memory can not be ignored. In general,

memory latency increases as memory frequency increases.

Therefore, compared with DDR 400 memory, although the DDR2 533

frequency is higher, but some DDR memory has a lower delay

parameter, so its performance is not different from that of the

ordinary DDR2 533.

2. the origin of memory frequency

Remember when we learned how the CPU clocked at CPU? The same

batch of CPU, before the standard model, they are "a milk mother

N cell embryo", in addition to different frequency, other

parameters are the same. For example, when the same batch of

Intel Core 2 Duo E4000 series production is good, manufacturers

will test these products. If the frequency of this CPU is steady

enough to reach a certain frequency, and this frequency is

exactly the level of the existing model CPU, then its model is

"armour"". If it reaches another frequency and is exactly the

level of the current model CPU B, the manufacturer is named "B"".

And so on, so all the CPU in this batch have been ordered.

So is the memory, when memory before the same batch without mark,

everyone is "N births", then like Samsung, modern production

plant will be the memory memory test, if the particles can be

stable to DDR2 800 level, then it will be named DDR2 800. The

same is true for DDR2 667 and DDR2 533.

Tip: during memory particle vendor testing, you will definitely

test memory particles that can run stably at a higher frequency

than DDR2 800. Because of its good performance, then the memory

manufacturers will by the high price of sold like Kingston,

Apacer and other memory module manufacturers. After the module

manufacturers buy these particles will also pick some good

quality electronic components and collocation, such a good

memory overclocking performance appeared in the market, the

price is much higher than ordinary memory.

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2008-4-7 15:21

Overclocking memory set, the price is not low

Which frequencies are often used indiscriminately?

Introduced the origin of memory frequency, below we begin to

learn the relation of a few kinds of memory frequency. At

present, there are three kinds of memory frequency, memory

frequency and kernel frequency.

1. particle core frequency

Students from the core frequency of these four words will know,

this is the basis of memory frequency, what the equivalent

frequency, frequency is based on it. We must remember the

following core frequency, DDR 266/DDR2 533/DDR3 1066 core

frequency is 133MHz, DDR 333/DDR2 667/DDR3 1333 core frequency

is 166MHz, DDR 400/DDR2 800/DDR3 1600 core frequency is 200MHz.

Tip: unconventional memory

This method is just for students to remember, and now for DDR,

DDR2, DDR3 apply. The three generation of memory, as long as

the values they follow are multiples, then the frequencies of

their particles are equal, and the frequencies in their

particles are equal to half of the values behind DDR. For

example, DDR 400, DDR2 800, and DDR3 1600, the values 400, 800

and 1600 behind them become multiples, and the frequency of

their particles is half the value of 400 in DDR 400, or 200.

2. working frequency

The core frequency that everyone remembers will be used

immediately in learning the memory operating frequency. The

memory operating frequency is two times the core frequency of

the particles. For example, the core frequency of DDR 400, DDR2

800, and DDR3 1600 is 200MHz, then the working frequency of the

three memory particles is 400MHz (the value is exactly 400 of

DDR 400). Why is it two times? In fact, it is related to the

principle of data transmission in DDR memory.

As shown in figure T, there is a working cycle of memory. Before

the memory of one cycle only in AB (rising edge) at the

transmission of data, then DDR memory is improved, not only in

the AB section of transmission data, still CD (falling edge)

period of data transmission, which is equivalent to a cycle of

two data transmission, DDR frequency doubled. Later DDR2, DDR3

memory have adopted this transmission principle, so appeared

DDR 400, DDR2 800, DDR3 1600 work frequency equal situation.

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2008-4-7 15:21

3. equivalent frequency

Finally, let's talk about the equivalent frequency, which is

actually the formal name of 800MHz in DDR2 800. To be exact,

it is related to the pre read of memory.

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2008-4-7 15:21

The frequency on the memory label is the equivalent frequency

The same is not difficult to understand pre reading, for example,

to see a person running fast or fast, depends on two aspects,

one is the pace, such as running two steps per second; the other

is the pace of the distance, such as every step run 1 meters.

The first person (DDR) per second more than two steps, each step

is 1 meters,

So it is the speed of 2 m / S; and second (DDR2) per second to

run two step (because DDR2 and DDR memory work frequency), each

is two meters, so the speed is 4 m / s. Second people are two

times as fast as the first.

So is the memory, DDR, DDR2, DDR3 memory frequency, so the speed

depends on the pace of DDR (pre reading), DDR pre read is 2bit,

which is the data transmission bandwidth (step distance). While

DDR2 4bit is pre read (DDR3 8bit), DDR2 "each distance is two

times of DDR, so as long as the memory work frequency, DDR2

equivalent frequency is 2 times the DDR equivalent frequency

is DDR, 4 times DDR3.

summary

Having said so much, Ms. Qi finally summed up several memory

frequency relationships in the following table. We can through

the table content that we usually say the equivalent frequency

is the frequency, such as the DDR2 800 equivalent frequency is

800MHz; while DDR 266, DDR2 533, DDR3 1066 equivalent frequency

is different, but because of DDR, DDR2, DDR3 in the pre reading

is different, so the frequency of DDR 266 and DDR2 533 particles,

the same as DDR3 1066 266MHz; memory core frequency is half the

frequency of memory.

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