Registers, which are very important memory cells in integrated circuits, usually consist of flip-flops. In integrated circuit design, registers can be divided into two types: registers used internally by the circuit and registers that serve as internal and external interfaces. The internal registers cannot be accessed by external circuits or software, but only store the function for the internal circuit or meet the timing requirements of the circuit. The interface registers can be accessed by internal circuits and external circuits or software at the same time. The registers in the CPU are one of them. As an interface between software and hardware, they are well-known to a wide range of general-purpose programming users.
Register features:1 register located in the CPU, very few, only 14
The data that 2 registers can store is not necessarily 8bit, some registers can store 16bit data, can store 32bit data to some registers in 386/486 processor
3 Each internal register has a name and no memory-like address number.
Data Register - Used to store integer numbers (refer to floating point registers below). In some simple/old CPUs, special data registers are accumulators used as mathematical calculations.
Address register - holds the memory address and is used to access the memory. In some simple/old CPUs, the special address register is an index register (one or more may occur).
General Purpose Registers (GPRs) - Both data or address can be saved, which means they are combined with data/address registers.
Floating Point Registers (FPRs) - Used to store floating point numbers.
Constant register - used to hold read-only values ​​(eg 0, 1, pi, etc.).
Vector register - used to store the data obtained by the vector processor running the SIMD (SingleInstrucTIon, MulTipleData) instruction.
Special Purpose Register - Stores data inside the CPU, such as the program counter (or instruction pointer), stack register, and status register (or microprocessor status word group).
Instruction register (instrucTIonregister) - store instructions that are now being run
Index register - is used to change the address of an operand when the program is run.
Under certain architectures, the mode indicating register (also referred to as "machine indicating register") stores and sets data related to the processor itself. Because their intention is to attach to the design of a particular processor, they are not expected to be the standard retained between microprocessor generations.
Registers and CPUs for extracting information from random access memory (stored register sets on different chips)
Memory buffer register (Memorybufferregister)
Memory data register (Memorydataregister)
Memory address register (Memoryaddressregister)
Memory Type Range Registers (MemoryTypeRangeRegisters)
The function of the register is very important, when the CPU deals with the data in the memory, often take the data to the internal register first, and then process again. The external register is a register for temporarily storing data in other parts of the computer. It exchanges data with the CPU through the "port". The external register has the dual characteristics of the register and the internal memory. Sometimes we often refer to external registers as "ports". This is not a strict statement, but it is often said.
Although external registers are also used to store data, the data it holds has special uses. The 0, 1 state of each bit in some registers reflects the working state or mode of the external device; there are also some bits in the register that can control the external device; there are also some ports as the path for the CPU to exchange data with the external device. So, the port is the bridge between the CPU and the peripherals. The CPU's access to the port is also based on the "number" (address) of the port, which is the same as accessing the memory. However, taking into account the number of peripherals connected to the machine is not much, so only 1024 port addresses are arranged in the design of the machine, the port address range is 0--3FFH.
Second, the memory profileMemory is one of the important components in the computer and it is a bridge to communicate with the CPU. All programs in the computer are run in memory, so the memory performance has a great impact on the computer. Memory is also referred to as internal memory. It is used to temporarily store computation data in the CPU and data exchanged with external memory such as a hard disk. As long as the computer is running, the CPU will transfer the data that needs to be calculated to the memory for calculation. When the operation is completed, the CPU will send the result out again, and the operation of the memory will also determine the stable operation of the computer. Memory is composed of memory chips, circuit boards, and gold fingers.
Memory capacity is the same as hard disk, floppy disk, and other memory capacity units. Their basic units are bytes (B), and:
1024B=1KB=1024 bytes=2^10 bytes (^ stands for power)
1024KB=1MB=1048576 bytes=2^20 bytes 1024MB=1GB=1073741824 bytes=2^30 bytes
1024GB=1TB=1099511627776 bytes=2^40 bytes
1024TB=1PB=1125899906842624 bytes=2^50 bytes
1024PB=1EB=1152921504606846976 bytes=2^60 bytes
1024EB=1ZB=1180591620717411303424 bytes=2^70 bytes
1024ZB=1YB=1208925819614629174706176 bytes=2^80 bytes
memory size:The type of memory and frequency of operation have a certain impact on performance, but in contrast, the impact of capacity is even greater. The larger the memory under the same configuration, the higher the machine performance. The price of memory went down slightly. Before and after 2011, the configuration of computer memory became larger and larger. Generally, it was above 1G, and there were computers with 2G, 4G, and 6G memory.
Memory is one of the important accessories in the computer. The size of the memory capacity can directly affect the performance of the entire system. Therefore, the memory capacity has been increasingly concerned by consumers. Especially in the current WIN7 operating system has begun to replace XP, for the latest WIN7 operating system, most consumers think that large-capacity memory score can be improved.
How memory works. From a functional perspective, we can think of memory as a bridge between a memory controller and a CPU, and memory is equivalent to a "warehouse." Obviously, the memory capacity determines the size of the "warehouse," and the speed of the memory determines the width of the "bridge." Both are indispensable. This is what we often call "memory capacity" and "memory speed."
The calculation method of memory bandwidth is not complicated. Everyone can follow the following formula: Bandwidth = bus width & TImes; bus frequency × number of packets exchanged in one clock cycle. Obviously, each of these multiplier factors will have a great impact on the final memory bandwidth. In the PCMarkVantage test, you can see that the 2GB and 4GB DDR3-1600 memory performance is relatively close, of which 2GB memory is only relatively backward when starting some office software, after all, less half the capacity so it is more difficult to run. In the 3DMarkVantage game performance test, we can see that in the Win7 system, the performance difference between 2GB and 4GB memory is not very big, the performance is very close. At the same time, in the WIN7 environment, the difference between 2GB memory and 4GB memory is very small, and there are even no differences in some cases. At this time, if you want to improve the memory performance, it is not significant to think about upgrading the capacity.
Workmanship is excellent
For the choice of memory, the most important is stability and performance, and the memory level of work directly affects performance, stability, and overclocking.
The quality of memory particles directly affects the performance of memory, and it can be said that it is also the most important core element of memory. Therefore, when buying, try to choose the memory chips produced by the big manufacturers. The common memory particle manufacturers are Samsung, Hyundai, Magnesium, South Asia, and Maoye, all of which have undergone a complete production process and are therefore of higher quality. Guaranteed. The memory quality performance of these top manufacturers' memory chips will inevitably be much higher than that of other brands of memory chips.
The role of the memory PCB circuit board is to connect the memory chip pins with the motherboard signal lines, so its work quality is directly related to system stability. At present, the mainstream memory PCB circuit board layer is generally 6 layers, this kind of circuit board has good electrical performance, can effectively shield signal interference. And better high-definition memory is often equipped with an 8-layer PCB circuit board for better performance.
SPD hidden information
SPD information can be said to be very important. It can directly reflect the memory performance and system. It stores information such as indicators for stable operation of the memory, as well as information on the production, manufacturers, etc. of the product. However, because each manufacturer can modify the SPD at will, many no-name memory manufacturers will modify the SPD parameters or directly COPY brand-name products SPD, but once the software is detected on the machine will be exposed.
Therefore, after purchasing the memory, everyone can go back and use common Everest, CPU-Z and other software to check it out. However, it should be noted that the SPD parameter is very important for large brand memory, but for no-name memory, the SPD information is not worth fully convincing.
Counterfeit Rework Products
At present, some memories often use different brands and models of memory particles, and everyone can see the difference at a glance. At the same time, some pervasive JS will also use the spurious method of grinding memory particles, and then add a new number parameter. However, if you look closely, you will find that the polished chips are bleak and have a feeling of fluffing, and the writing on the stamps is not clear. These are generally fake memory products that require attention.
In addition, we must also observe whether the PCB circuit board is clean, with no glitches, etc., whether the gold finger has obvious traces left after insertion and removal, and if so, it is very likely that the memory product will be returned (and certainly not excluded). The factory was tested before leaving the factory, but it was quite a few). What needs to be reminded is that no matter how cheap the returned and counterfeit memory is, it is not worth buying, because its security risks are very serious.
Distance is not the main factor, but it is best to understand, so put it first. Memory is far from the CPU, so it takes longer to read.
Taking a 3GHz CPU as an example, the current can oscillate 3 billion times per second, each time about 0.33 nanoseconds. Light can travel 30 centimeters in 1 nanosecond. That is, light can travel 10 centimeters within one clock cycle of the CPU. Therefore, if the memory is more than 5 centimeters from the CPU, it is impossible to complete the reading of the data within one clock cycle. This has not considered the hardware limitations and the current does not actually reach the speed of light. In contrast, registers are internal to the CPU and of course read faster.
Distance has a great impact on desktop computers and has a much smaller impact on mobile phones. The clock frequency of the mobile phone CPU is relatively slow (1.3GHz for the iPhone5s), and the memory of the mobile phone is close to the CPU.
Reason two: different hardware designsApple’s new iPhone 5s, CPU A7, registers more than 6000 bits (31 64-bit registers plus 32 128-bit registers). The memory of the iPhone 5s is 1GB, which is about 8 billion bits. This means that high-performance, high-cost, power-hungry designs can be used on registers, but there are only more than 6,000 bits and cannot be used in memory. Because the cost and energy consumption of each bit only increase a little, it will be amplified by 8 billion times.
In fact, this is indeed the case. The design of the memory is relatively simple. Each bit is a capacitor and a transistor, and the design of the register is completely different, with several more electronic components. After the power is turned on, the transistor of the register is always charged, and the transistor of the memory is used only when it is used, and no electricity is used when it is not used, which is advantageous for power saving. These design factors determine that registers are faster than memory reads.
Reason 3: Different ways of workingRegisters work in a simple way, with only two steps: (1) finding the relevant bits, and (2) reading these bits.
The way memory works is much more complicated:
(1) find the data pointer. (The pointer may be stored in a register, so this step already includes all the work of the register.)
(2) The pointer is sent to a memory management unit (MMU), which translates the virtual memory address into an actual physical address.
(3) The physical address is sent to a memory controller, and the memory controller finds out which memory bank the address is in.
(4) Determine which memory chunk the data is on and read the data from the chunk.
(5) The data is sent back to the memory controller, back to the CPU, and then used.
The memory workflow is many more steps than the register. Each step creates a delay, which accumulates to make the memory much slower than the register.
In order to ease the huge speed difference between registers and memory, hardware designers have made many efforts, including setting the cache inside the CPU, optimizing the working mode of the CPU, reading all the data needed for the instructions from the memory as much as possible, and so on.
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