EDO is the abbreviation of extended data output. It cancels the time interval between two storage cycles of motherboard and memory, and transmits data every two clock cycles, which greatly shortens the access time and improves the access speed by 30% to 60ns. EDO memory is mainly used for 72-wire SIMM memory chips and PCI graphics cards with EDO memory chips. This kind of memory is very popular in 486 and early Pentium computer systems. Divided into 72 lines and 168 lines. Its working voltage is 5V and its bandwidth is 32 bits. Two or four rows must be used in pairs. It can be used on the motherboard of Intel 430FX/430VX or even 430TX chipset. At present, it has also been eliminated and can only be seen on some old machines.
SDRAM is the abbreviation of synchronous dynamic random access memory, and it is a widely used memory form in previous years. SDRAM uses a working voltage of 3.3v and a bandwidth of 64 bits. SDRAM locks CPU and RAM together through the same clock, so that RAM and CPU can enjoy a clock cycle and work synchronously at the same speed, which can be 50% faster than EDO memory. SDRAM is based on dual bank structure, which includes two staggered memory arrays. When the CPU accesses data from one memory bank or array, the other is ready to read and write data. By tightly switching these two memory arrays, the reading efficiency can be doubled. SDRAM is not only used as main memory, but also widely used in video memory on graphics cards. SDRAM used to be the mainstream memory for a long time, and it was supported from 430TX chipset to 845 chipset. But with the popularization of DDR SDRAM, SDRAM is gradually withdrawing from the mainstream market.
DDR SDRAM is the abbreviation of double data rate synchronous dynamic random access memory, which is a memory standard proposed by VIA and other companies to compete with RDRAM. DDR SDRAM is an updated product of SDRAM, which uses a working voltage of 2.5v It allows data transmission at the rising and falling edges of clock pulses, so that the speed of SDRAM can be doubled without increasing the clock frequency, and the transmission rate and memory bandwidth are twice that of SDRAM. For example, compared with PC 133 SDRAM, the working frequency is also 133MHz, but memory bandwidth reaches 2. 12 GB/s, which is twice as high as PC 133 SDRAM. At present, mainstream chipsets support DDR SDRAM, which is the most commonly used memory type.
DDR2 (Double Data Rate 2) SDRAM is a new generation of memory technology standard developed by JEDEC (Joint Committee on Electronic Equipment Engineering). The biggest difference between DDR2 and the previous generation memory technology standard is that although the basic mode of data transmission is adopted while the clock rises/falls, the pre-reading ability of DDR 2 memory is twice that of the previous generation DDR memory (that is, 4-4bit data reading and prefetching). In other words, DDR2 memory can read/write data at 4 times the speed of external bus and run at 4 times the speed of internal control bus.
In addition, because DDR2 standard stipulates that DDR2 memories are all packaged in FBGA, FBGA packaging can provide better electrical performance and heat dissipation, which provides a solid foundation for the stable operation and future frequency development of DDR2 memories, which is different from TSOP/TSOP-II packaging widely used at present. Looking back on the development of DDR, from the first generation of DDR200 applied to personal computers through DDR266 and DDR333 to today's dual-channel DDR400 technology, the development of the first generation of DDR has reached the technical limit, and it is difficult to improve the working speed of memory by conventional methods. With the development of Intel's latest processor technology, the front-end bus has higher and higher requirements for memory bandwidth, and it will be the general trend to have DDR2 memory with higher and more stable working frequency.
RDRAM is the abbreviation of Rambus dynamic random access memory, which is a memory with system bandwidth and inter-chip interface design developed by Rambus company. It can transmit data through a simple bus in a very high frequency range, and at the same time use low-voltage signals to transmit data at two edges of high-speed synchronous clock pulses. At first, the Intel 820 chipset supported RDRAM, and then there were 840,850 chipsets and so on. RDRAM was initially strongly supported by Intel, but due to its high price and patent licensing restrictions of Rambus, it has not been able to become the mainstream of the market, and its position was quickly replaced by DDR SDRAM, which is relatively cheap and has the same excellent performance, with a small market share.