MemoryMemory

RAM and CACHERAM and CACHE

RAMRAM

Stands for Random Access MemoryStands for Random Access Memory It is volatile in natureIt is volatile in nature

Loses its contents if the power is turned offLoses its contents if the power is turned off Holds data and programs the CPU is Holds data and programs the CPU is

usingusing Main memory for the computerMain memory for the computer Scan be shared with other devices, such Scan be shared with other devices, such

as videoas video

Amount of RAMAmount of RAM

Measured in MegaBytes (MB)Measured in MegaBytes (MB) The general rule of thumb is to install The general rule of thumb is to install

as much RAM as you can affordas much RAM as you can afford Upgrading RAM can speed up a slow Upgrading RAM can speed up a slow

systemsystem

Minimum Amounts of RAMMinimum Amounts of RAM

DOS 6.2 – 640 KBDOS 6.2 – 640 KB Windows 3.x – 1 MBWindows 3.x – 1 MB Windows 95 – 8 MBWindows 95 – 8 MB Windows 98 – 16 MBWindows 98 – 16 MB Windows 2000 – 64 MBWindows 2000 – 64 MB Windows XP – 64 MBWindows XP – 64 MB

Types of RAMTypes of RAM

SRAMSRAM Static Random Access MemoryStatic Random Access Memory Uses transistorsUses transistors Large and expensive, but fastLarge and expensive, but fast

DRAMDRAM Dynamic Random Access MemoryDynamic Random Access Memory Uses capacitorsUses capacitors Small and affordable, but slower than Small and affordable, but slower than

SRAMSRAM

Drawbacks of DRAMDrawbacks of DRAM

The small capacitors need constant The small capacitors need constant power to keep them from fadingpower to keep them from fading

This process of charging is called This process of charging is called RefreshRefresh

Most DRAM needs to be refreshed Most DRAM needs to be refreshed every 2 msevery 2 ms

DRAM TypesDRAM Types

Started with DIP (Dual Inline Started with DIP (Dual Inline Pin) socket typesPin) socket types Small amount of memory Small amount of memory

(>1MB)(>1MB) Next advancement was SIPP Next advancement was SIPP

(Single Inline Pin Package(Single Inline Pin Package Extinct because the pins were Extinct because the pins were

easy to bend and breakeasy to bend and break

DRAM TypesDRAM Types

Changed styles to a SIMM (Single Changed styles to a SIMM (Single Inline Memory Module)Inline Memory Module) Small amounts of DIP chips on a single Small amounts of DIP chips on a single

boardboard Used with 80286 – 80486 CPU’sUsed with 80286 – 80486 CPU’s Two different styles – 30 pin and 72 pinTwo different styles – 30 pin and 72 pin

30 Pin SIMM30 Pin SIMM

Has contacts on both sides of the Has contacts on both sides of the modulemodule

Only contacts one sideOnly contacts one side Used in later 80286 and 80386 Used in later 80286 and 80386

CPU’sCPU’s

72 Pin SIMM72 Pin SIMM

Has contacts on both sides of the Has contacts on both sides of the modulemodule

Only contacts one sideOnly contacts one side Notch in the middle of the chipNotch in the middle of the chip Used in later 80386 and 80486 Used in later 80386 and 80486

CPU’sCPU’s

Two Types Of 72 Pin SIMM’sTwo Types Of 72 Pin SIMM’s

FPM (Fast Page FPM (Fast Page Mode)Mode) Arranges memory Arranges memory

in rows and in rows and columnscolumns

Older style of DRAMOlder style of DRAM Used in few Used in few

motherboardsmotherboards

EDO (Extended EDO (Extended Data Output)Data Output) Allows access while Allows access while

an output is an output is occurringoccurring

Standardized DRAMStandardized DRAM Used in many Used in many

motherboardsmotherboards

168 Pin DIMM168 Pin DIMM

Next DRAM was the DIMM (Dual Next DRAM was the DIMM (Dual Inline Memory Module)Inline Memory Module) 168 pins long (84 contacts per side)168 pins long (84 contacts per side) Also called SDRAM (Synchronous Also called SDRAM (Synchronous

DRAM)DRAM) Runs at the same speed as the Runs at the same speed as the

processorprocessor

Newer Types of SDRAMNewer Types of SDRAM

Next DRAM was the DDR-SDRAMNext DRAM was the DDR-SDRAM Double Data Rate Synchronous DRAMDouble Data Rate Synchronous DRAM Twice as fast as SDRAMTwice as fast as SDRAM Current industry standardCurrent industry standard Will not interchange with SDRAMWill not interchange with SDRAM

Newest SDRAMNewest SDRAM

RambusRambus Also called DRDRAM Also called DRDRAM

and RIMMand RIMM Runs at 400 Mhz, fastest Runs at 400 Mhz, fastest

of all RAM of all RAM All memory slots on the All memory slots on the

motherboard must be filledmotherboard must be filled Unused slots must have Unused slots must have

continuity modules installedcontinuity modules installed

Installation of DRAMInstallation of DRAM

Type of DRAMType of DRAM 30 pin SIMM’s 30 pin SIMM’s 72 pin SIMM’s72 pin SIMM’s 168 pin DIMM’s168 pin DIMM’s DDR-SDRAMDDR-SDRAM RambusRambus

Amount Amount RequiredRequired

4 to a set4 to a set 2 to a set2 to a set Single modulesSingle modules Single modulesSingle modules All slots filledAll slots filled

Installation of DRAMInstallation of DRAM

Install DRAM starting from socket 0 or 1Install DRAM starting from socket 0 or 1 Some motherboards have a Some motherboards have a

combination of socket typescombination of socket types Some of these sockets are shared, see the Some of these sockets are shared, see the

documentationdocumentation Use the same type of DRAM in the setsUse the same type of DRAM in the sets Seat firmly until they snap into placeSeat firmly until they snap into place

Installation of DRAMInstallation of DRAM

After installation, enter the CMOS After installation, enter the CMOS and check for the installed memoryand check for the installed memory

Watch the memory count and Watch the memory count and compare with the amount you compare with the amount you installedinstalled

Bus Width of SDRAMBus Width of SDRAM

(2) Parity 72 pin (2) Parity 72 pin SIMMSIMM

(2) non-parity 72 (2) non-parity 72 pin SIMMpin SIMM

Parity 168 pin Parity 168 pin DIMMDIMM

Non-parity 168 pin Non-parity 168 pin DIMMDIMM

72 bit72 bit

64 bit64 bit 72 bit72 bit

64 bit64 bit

Other MemoryOther Memory VRAM (Video RAM)VRAM (Video RAM) WRAM (Windows RAM)WRAM (Windows RAM)

Both designed for video applicationsBoth designed for video applications Are double ported, meaning that 2 chips Are double ported, meaning that 2 chips

can access them at the same timecan access them at the same time RAMDAC (RAM Digital to Analog RAMDAC (RAM Digital to Analog

Converter)Converter) Used to convert digital signals to the Used to convert digital signals to the

monitor (for each color – red, green, and monitor (for each color – red, green, and blue)blue)

CACHE memoryCACHE memory

Two types of CacheTwo types of Cache L1 (Level 1) which is mounted on the L1 (Level 1) which is mounted on the

CPU chipCPU chip L2 (Level 2) which is mounted on the L2 (Level 2) which is mounted on the

motherboard (or on the die with some motherboard (or on the die with some CPU’s)CPU’s)

L1 CacheL1 Cache

The fastest memoryThe fastest memory Used to store frequently used Used to store frequently used

information that the CPU needsinformation that the CPU needs Part of the CPU chipPart of the CPU chip Uses SRAM technologyUses SRAM technology

Standard L1 Cache SizesStandard L1 Cache Sizes

8048680486 80486DX480486DX4 PentiumPentium Pentium MMXPentium MMX Pentium ProPentium Pro Pentium 2Pentium 2 CeleronCeleron Pentium 3Pentium 3

8KB8KB 16KB16KB 16KB16KB 32KB32KB 16KB16KB 32KB32KB 32KB32KB 32KB32KB

L2 CacheL2 Cache

Next fastest memoryNext fastest memory Used to store frequently used Used to store frequently used

information that cannot be held in L1 information that cannot be held in L1 cachecache

On the CPU board (Pentium Pro and On the CPU board (Pentium Pro and Pentium 2)Pentium 2)

On the motherboardOn the motherboard Uses SRAM technologyUses SRAM technology

Standard L2 Cache SizesStandard L2 Cache Sizes

8048680486 80486DX480486DX4 PentiumPentium Pentium MMXPentium MMX Pentium ProPentium Pro Pentium 2Pentium 2 CeleronCeleron Pentium 3Pentium 3

0KB0KB 0KB0KB 0KB0KB 0KB0KB 256KB256KB 512KB512KB 0KB0KB 512KB512KB

COAST ModulesCOAST Modules

Some Pentium motherboards used L2 Some Pentium motherboards used L2 cache boards called COAST modulescache boards called COAST modules

Looked like a DIMM except they are Looked like a DIMM except they are shorter and tallershorter and taller

Used Pipeline-Burst modeUsed Pipeline-Burst mode