Memory RAM and CACHE

RAM Stands for Random Access Memory Stands for Random Access Memory It is volatile in nature It is volatile in nature Loses its contents if the power is turned off Loses its contents if the power is turned off Holds data and programs the CPU is using Holds data and programs the CPU is using Main memory for the computer Main memory for the computer Scan be shared with other devices, such as video Scan be shared with other devices, such as video

Amount of RAM Measured in MegaBytes (MB) Measured in MegaBytes (MB) The general rule of thumb is to install as much RAM as you can afford The general rule of thumb is to install as much RAM as you can afford Upgrading RAM can speed up a slow system Upgrading RAM can speed up a slow system

Minimum Amounts of RAM DOS 6.2 – 640 KB DOS 6.2 – 640 KB Windows 3.x – 1 MB Windows 3.x – 1 MB Windows 95 – 8 MB Windows 95 – 8 MB Windows 98 – 16 MB Windows 98 – 16 MB Windows 2000 – 64 MB Windows 2000 – 64 MB Windows XP – 64 MB Windows XP – 64 MB

Types of RAM SRAM SRAM Static Random Access Memory Static Random Access Memory Uses transistors Uses transistors Large and expensive, but fast Large and expensive, but fast DRAM DRAM Dynamic Random Access Memory Dynamic Random Access Memory Uses capacitors Uses capacitors Small and affordable, but slower than SRAM Small and affordable, but slower than SRAM

Drawbacks of DRAM The small capacitors need constant power to keep them from fading The small capacitors need constant power to keep them from fading This process of charging is called Refresh This process of charging is called Refresh Most DRAM needs to be refreshed every 2 ms Most DRAM needs to be refreshed every 2 ms

DRAM Types Started with DIP (Dual Inline Pin) socket types Started with DIP (Dual Inline Pin) socket types Small amount of memory (>1MB) Small amount of memory (>1MB) Next advancement was SIPP (Single Inline Pin Package Next advancement was SIPP (Single Inline Pin Package Extinct because the pins were easy to bend and break Extinct because the pins were easy to bend and break

DRAM Types Changed styles to a SIMM (Single Inline Memory Module) Changed styles to a SIMM (Single Inline Memory Module) Small amounts of DIP chips on a single board Small amounts of DIP chips on a single board Used with – CPU’s Used with – CPU’s Two different styles – 30 pin and 72 pin Two different styles – 30 pin and 72 pin

30 Pin SIMM Has contacts on both sides of the module Has contacts on both sides of the module Only contacts one side Only contacts one side Used in later and CPU’s Used in later and CPU’s

72 Pin SIMM Has contacts on both sides of the module Has contacts on both sides of the module Only contacts one side Only contacts one side Notch in the middle of the chip Notch in the middle of the chip Used in later and CPU’s Used in later and CPU’s

Two Types Of 72 Pin SIMM’s FPM (Fast Page Mode) FPM (Fast Page Mode) Arranges memory in rows and columns Arranges memory in rows and columns Older style of DRAM Older style of DRAM Used in few motherboards Used in few motherboards EDO (Extended Data Output) EDO (Extended Data Output) Allows access while an output is occurring Standardized DRAM Used in many motherboards

168 Pin DIMM Next DRAM was the DIMM (Dual Inline Memory Module) Next DRAM was the DIMM (Dual Inline Memory Module) 168 pins long (84 contacts per side) 168 pins long (84 contacts per side) Also called SDRAM (Synchronous DRAM) Also called SDRAM (Synchronous DRAM) Runs at the same speed as the processor Runs at the same speed as the processor

Newer Types of SDRAM Next DRAM was the DDR-SDRAM Next DRAM was the DDR-SDRAM Double Data Rate Synchronous DRAM Double Data Rate Synchronous DRAM Twice as fast as SDRAM Twice as fast as SDRAM Current industry standard Current industry standard Will not interchange with SDRAM Will not interchange with SDRAM

Newest SDRAM Rambus Rambus Also called DRDRAM and RIMM Also called DRDRAM and RIMM Runs at 400 Mhz, fastest of all RAM Runs at 400 Mhz, fastest of all RAM All memory slots on the motherboard must be filled All memory slots on the motherboard must be filled Unused slots must have continuity modules installed Unused slots must have continuity modules installed

Installation of DRAM Type of DRAM 30 pin SIMM’s 30 pin SIMM’s 72 pin SIMM’s 72 pin SIMM’s 168 pin DIMM’s 168 pin DIMM’s DDR-SDRAM DDR-SDRAM Rambus Rambus Amount Required 4 to a set 4 to a set 2 to a set 2 to a set Single modules Single modules All slots filled All slots filled

Installation of DRAM Install DRAM starting from socket 0 or 1 Install DRAM starting from socket 0 or 1 Some motherboards have a combination of socket types Some motherboards have a combination of socket types Some of these sockets are shared, see the documentation Some of these sockets are shared, see the documentation Use the same type of DRAM in the sets Use the same type of DRAM in the sets Seat firmly until they snap into place Seat firmly until they snap into place

Installation of DRAM After installation, enter the CMOS and check for the installed memory After installation, enter the CMOS and check for the installed memory Watch the memory count and compare with the amount you installed Watch the memory count and compare with the amount you installed

Bus Width of SDRAM (2) Parity 72 pin SIMM (2) Parity 72 pin SIMM (2) non-parity 72 pin SIMM (2) non-parity 72 pin SIMM Parity 168 pin DIMM Parity 168 pin DIMM Non-parity 168 pin DIMM Non-parity 168 pin DIMM 72 bit 72 bit 64 bit 64 bit 72 bit 72 bit 64 bit 64 bit

Other Memory VRAM (Video RAM) VRAM (Video RAM) WRAM (Windows RAM) WRAM (Windows RAM) Both designed for video applications Both designed for video applications Are double ported, meaning that 2 chips can access them at the same time Are double ported, meaning that 2 chips can access them at the same time RAMDAC (RAM Digital to Analog Converter) RAMDAC (RAM Digital to Analog Converter) Used to convert digital signals to the monitor (for each color – red, green, and blue) Used to convert digital signals to the monitor (for each color – red, green, and blue)

CACHE memory Two types of Cache Two types of Cache L1 (Level 1) which is mounted on the CPU chip L1 (Level 1) which is mounted on the CPU chip L2 (Level 2) which is mounted on the motherboard (or on the die with some CPU’s) L2 (Level 2) which is mounted on the motherboard (or on the die with some CPU’s)

L1 Cache The fastest memory The fastest memory Used to store frequently used information that the CPU needs Used to store frequently used information that the CPU needs Part of the CPU chip Part of the CPU chip Uses SRAM technology Uses SRAM technology

Standard L1 Cache Sizes DX DX4 Pentium Pentium Pentium MMX Pentium MMX Pentium Pro Pentium Pro Pentium 2 Pentium 2 Celeron Celeron Pentium 3 Pentium 3 8KB 8KB 16KB 16KB 32KB 32KB 16KB 16KB 32KB 32KB

L2 Cache Next fastest memory Next fastest memory Used to store frequently used information that cannot be held in L1 cache Used to store frequently used information that cannot be held in L1 cache On the CPU board (Pentium Pro and Pentium 2) On the CPU board (Pentium Pro and Pentium 2) On the motherboard On the motherboard Uses SRAM technology Uses SRAM technology

Standard L2 Cache Sizes DX DX4 Pentium Pentium Pentium MMX Pentium MMX Pentium Pro Pentium Pro Pentium 2 Pentium 2 Celeron Celeron Pentium 3 Pentium 3 0KB 0KB 256KB 256KB 512KB 512KB 0KB 0KB 512KB 512KB

COAST Modules Some Pentium motherboards used L2 cache boards called COAST modules Some Pentium motherboards used L2 cache boards called COAST modules Looked like a DIMM except they are shorter and taller Looked like a DIMM except they are shorter and taller Used Pipeline-Burst mode Used Pipeline-Burst mode