Motherboard/Processor/Memory There are different slots and sockets for CPUs, and it is necessary for a motherboard to have the appropriate slot or socket for the CPU. Most sockets are square. Several precautions are taken to ensure that both the socket and the processor are indicated to ensure proper orientation. The processor is usually marked with a dot or a notch in the corner that is intended to go into the marked corner of the socket. Sockets and slots on the motherboard are as plentiful and varied as processors. The three most popular are the Socket 5 and Socket 7, and the Single Edge Contact Card (SECC). Socket 5 and Socket 7 CPU sockets are basically flat and have several rows of holes arranged in a square. The SECC connectors are of two types: slot 1 & slot 2. Design No of Pins Pin Rows Voltage Mobo Class Processor's supported Socket 1 169 3 5 Volts 486 80486SX, 80486DX, 80486DX2, 80486DX4 Socket 2 238 4 5 Volts 486 80486SX, 80486DX, 80486DX2, 80486DX4 Socket 3 237 4 5 / 3.3 Volts 486 80486SX, 80486DX, 80486DX2, 80486DX4 Socket 4 273 4 5 Volts 1st Generation Pentium Pentium 60-66, Pentium OverDrive Socket 5 320 5 3.3 Volts Pentium Pentium 75-133 MHz, Pentium OverDrive Socket 6 235 4 3.3 Volts 486 486DX4, Pentium OverDrive Design No of Pins Pin Rows Voltage Mobo Class Processor's supported Socket 7 321 5 2.5 / 3.3Volts Pentium 75-200 MHz, OverDrive, Pentium MMX Socket 8 387 5 (dual pattern) 3.1 / 3.3Volts Pentium Pro Pentium Pro OverDrive, Pentium II OverDrive Intel Slot 1 242 N/a 2.8 / 3.3Volts Pentium Pro / Pentium II Pentium II, Pentium Pro, Celeron. Intel Slot 2 330 N/a 2.8/ 3.3Volts Intel Xeon Pentium II 400,450, Pentium Xeon Socket 370 370 N/a 2.0 Volts Celeron Celeron, Pentium IIIs Socket 423 423 N/a 1.0/1.85 Volts Pentium IV Celeron, Pentium Iv Socket 479 479 - - Pentium M Pentium M AMD ATHLON PROCESSORS Slot A - Original AMD Athlon processors Socket 462 - Newer AMD Athlon, Athlon XP, Sempron, and Duron processors Socket 754 - Lower end AMD Athlon 64 and Sempron processors with single-channel memory support Socket 939 - AMD Athlon 64 and AMD Athlon FX processors with dual-channel memory support Socket 940 - AMD Opteron and early AMD Athlon FX processors Different kinds of SLOTS y Slot 1 - Celeron, Pentium II, Pentium III y Slot 2 - Pentium II Xeon, Pentium III Xeon y Slot A - Early Athlons y Slot B - DEC Alpha Different kinds of SOCKETS y Socket 1 - 486 y Socket 2 - 486 y Socket 3 - 486 y Socket 4 - Early Pentiums (60-66) y Socket 5 - Pentium, IDT Winchip C6, Winchip 2 y Socket 463 - (also known as Socket NexGen) - NexGen Nx586 y Socket 6 - Intel 80486 y Socket 7 - Pentium y Super Socket 7 - Faster Bus Speed - AMD K6-2, K6-III, Rise mP6 y Socket 8 - Pentium Pro y Socket 370 - Celeron, Pentium III, Cyrix III y Socket 423 - Pentium 4 but short lived y Socket 478 - Intel Celeron, Pentium 4 y Socket 479 - Mobile Pentium y Socket 775 - (also known as LGA 775 or Socket T) - Intel Pentium 4 VRM (Voltage Regulator Module) is used for supplying proper voltage to the processor for its operation. A VRM (Voltage Regulator Module) is installed in Header 8 on the motherboard. Most VRMs have VID (Voltage ID). VID allows the processor to program the correct voltage during power-on. If the motherboard has Header 8, then a VRM must be installed in the header to power the processor. High-performance computers use multiple microprocessors to satisfy the computing speeds. The applications use one VRM for each microprocessor to take advantage of the modularity and economy offered by the VRM. These multiple VRMS are designed to share the total current demand of the processors. MEMORY RAM - Random Access Memory is a collection of memory chips, which function as the computer's primary workspace. In today's computer, 64MB (64 megabytes) of SDRAM is a minimum for a desktop computer. y Masked ROMs: The very first ROMs were hardwired devices the contents of which had to be specified before chip production. They are now called masked ROMs to distinguish them from other types of ROM. y PROM: One step up from the masked ROM is the PROM (programmable ROM. A Device programmer is used for writing the data to the PROM; it writes data one word at a time by applying an electrical charge to the input pins of the chip. Once programmed the PROM's contents can never be changed. y EPROM (erasable-and-programmable ROM): is programmed in the same manner as a PROM. The advantage EPROM has over PROM is that it can be erased and reprogrammed repeatedly. Data on an EPROM is erased by exposing it to a strong source of ultraviolet light which resets EPROM to its initial un-programmed state. Hybrid memories are developed that can be read and written as desired just like RAM, but maintain their contents without electrical power, just like ROM. EEPROM and flash are descendants of ROM devices. These are typically used to store code. The third hybrid, NVRAM, is a modified version of SRAM. NVRAM holds persistent data. y EEPROM: Electrically-erasable-and-programmable. In EEPROMs the erase operation is accomplished electrically, rather than exposure to ultraviolet light. Flash memory devices are high density, low cost, nonvolatile, fast (to read, but not to write), and electrically reprogrammable. The technologies for flash and EEPROM are similar. The major difference is that flash devices can only erase sector by sector but not byte by byte. Typical sector sizes are in the range 256 bytes to 16KB. Despite this disadvantage, flash is much more popular than EEPROM due to its advantages. y NVRAM: Non-volatile RAM is the third member of Hybrid memory class. NVRAM has similar characteristics as hybrid memories discussed previously but it is physically different. An NVRAM is usually just an SRAM with a battery backup. When the power is turned on, the NVRAM operates just like any other SRAM. When the power is turned off, the NVRAM draws just enough power from the battery to retain its data. NVRAM application is limited due to its high cost. There are two types of RAM: 1. Static RAM (SRAM) retains its contents as long as electrical power is applied to the chip. If the power even if lost temporarily, its contents will be lost forever. They are faster than DRAM but are expensive. SRAM is used only where access speed is extremely important. 2. Dynamic RAM (DRAM) has an extremely short data lifetime-typically about four milliseconds. They are effective whenever large amounts of RAM are required. Apart from SRAM and DRAM, there are EDO RAM, VRAM (Designed for graphics), SDRAM (next level of DRAM), DDR RAM (Next level of SDRAM) and RDRAM. History of Memory with: Speed Number of Pins Year Introduced Technology Speed Limit Form Factor 1987 FPM 50ns 30- or 72-pin SIMM 1995 EDO 50ns 72-pin or 168-pin DIMM 1996 PC66 SDRAM 66MHz 168-pin DIMM 1998 PC100 SDRAM 100MHz 168-pin DIMM 1999 RDRAM 800MHz 184-Pin RIMM 1999/2000 PC133 SDRAM 133MHz 168-pin DIMM 2000 DDR SDRAM 266MHz 184-pin DIMM 3. EDO (Extended Data Out) RAM: y Increases performance up to 15 percent over DRAM by eliminating memory wait states, this means eliminating few steps to access memory. y Extends the availability of data in the memory as the read time does not expire until an additional signal is sent to the chip. Hence it is called an Extended Data Out RAM. In comparison a DRAM discharges its contents after read and must be refreshed before another read can occur. y Is more expensive than DRAM, but less expensive than SDRAM. EDO RAM comes in 72-pin SIMMs and sometimes even on 168-pin DIMMs (dual inline memory modules). 4. DRAM (Dynamic random access memory): y Is an enhancement over SRAM. DRAM has a different approach towards storing the 1s and 0s. DRAM stores information as charges in very small capacitors, instead of transistors. y Stores each bit of data in a separate capacitor. If a charge exists in a capacitor, it's interpreted as a 1. The absence of a charge will be interpreted as a 0. y Uses capacitors instead of switches. As the capacitor leaks electrons, the information gets lost eventually, unless the charge is refreshed periodically, therefore it uses a constant refresh signal to keep the information in memory. Because it must be refreshed periodically, it is called dynamic memory. y Needs more power than SRAM to refresh signals, therefore, is mostly found in desktop computers. y Uses several memory units called cells. These cells are packed with very high density. Hence, these chips can hold large amounts of data. y Also known as FPM (fast page mode) DRAM, it comes in 80, 70 or 60 nanosecond (ns) speeds.A Takes two processor wait-states each time a read or write takes place. The advantage is that, it's compatible with just about everything. Disadvantage is that it's the slowest of the memory types currently available and because it isn't in demand, it's now more expensive than faster memory alternatives such as EDO and SDRAM. y Is available on industry standard 30- or 72-pin Single Inline Memory Modules (SIMMs). DRAM is also available in DIMMs (Dual Inline Memory Modules). y 5.