Transcript Memory

Memory
RAM and CACHE
RAM
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Stands for Random Access Memory
It is volatile in nature
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Loses its contents if the power is turned off
Holds data and programs the CPU is using
Main memory for the computer
Scan be shared with other devices, such
as video
Amount of RAM
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Measured in MegaBytes (MB)
The general rule of thumb is to install as
much RAM as you can afford
Upgrading RAM can speed up a slow
system
Minimum Amounts of RAM
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DOS 6.2 – 640 KB
Windows 3.x – 1 MB
Windows 95 – 8 MB
Windows 98 – 16 MB
Windows 2000 – 64 MB
Windows XP – 64 MB
Types of RAM
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SRAM
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Static Random Access Memory
Uses transistors
Large and expensive, but fast
DRAM
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Dynamic Random Access Memory
Uses capacitors
Small and affordable, but slower than SRAM
Drawbacks of DRAM
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The small capacitors need constant power
to keep them from fading
This process of charging is called Refresh
Most DRAM needs to be refreshed every 2
ms
DRAM Types
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Started with DIP (Dual Inline Pin)
socket types
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Small amount of memory (>1MB)
Next advancement was SIPP
(Single Inline Pin Package
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Extinct because the pins were easy
to bend and break
DRAM Types
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Changed styles to a SIMM (Single Inline
Memory Module)
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Small amounts of DIP chips on a single board
Used with 80286 – 80486 CPU’s
Two different styles – 30 pin and 72 pin
30 Pin SIMM
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Has contacts on both sides of the
module
Only contacts one side
Used in later 80286 and 80386 CPU’s
72 Pin SIMM
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Has contacts on both sides of the module
Only contacts one side
Notch in the middle of the chip
Used in later 80386 and 80486 CPU’s
Two Types Of 72 Pin SIMM’s
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FPM (Fast Page Mode)
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Arranges memory in
rows and columns
Older style of DRAM
Used in few
motherboards
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EDO (Extended Data
Output)
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Allows access while an
output is occurring
Standardized DRAM
Used in many
motherboards
168 Pin DIMM
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Next DRAM was the DIMM (Dual Inline
Memory Module)
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168 pins long (84 contacts per side)
Also called SDRAM (Synchronous DRAM)
Runs at the same speed as the processor
Newer Types of SDRAM
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Next DRAM was the DDR-SDRAM
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Double Data Rate Synchronous DRAM
Twice as fast as SDRAM
Current industry standard
Will not interchange with SDRAM
Newest SDRAM
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Rambus
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Also called DRDRAM
and RIMM
Runs at 400 Mhz, fastest
of all RAM
All memory slots on the
motherboard must be filled
Unused slots must have continuity
modules installed
Installation of DRAM
Type of DRAM
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30 pin SIMM’s
72 pin SIMM’s
168 pin DIMM’s
DDR-SDRAM
Rambus
Amount Required
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4 to a set
2 to a set
Single modules
Single modules
All slots filled
Installation of DRAM
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Install DRAM starting from socket 0 or 1
Some motherboards have a combination
of socket types
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Some of these sockets are shared, see the
documentation
Use the same type of DRAM in the sets
Seat firmly until they snap into place
Installation of DRAM
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After installation, enter the CMOS and
check for the installed memory
Watch the memory count and compare
with the amount you installed
Bus Width of SDRAM
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(2) Parity 72 pin
SIMM
(2) non-parity 72 pin
SIMM
Parity 168 pin DIMM
Non-parity 168 pin
DIMM
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72 bit
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64 bit
72 bit
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64 bit
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Other Memory
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VRAM (Video RAM)
WRAM (Windows RAM)
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Both designed for video applications
Are double ported, meaning that 2 chips can
access them at the same time
RAMDAC (RAM Digital to Analog
Converter)
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Used to convert digital signals to the monitor
(for each color – red, green, and blue)
CACHE memory
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Two types of Cache
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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)
L1 Cache
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The fastest memory
Used to store frequently used information
that the CPU needs
Part of the CPU chip
Uses SRAM technology
Standard L1 Cache Sizes
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80486
80486DX4
Pentium
Pentium MMX
Pentium Pro
Pentium 2
Celeron
Pentium 3
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8KB
16KB
16KB
32KB
16KB
32KB
32KB
32KB
L2 Cache
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Next fastest memory
Used to store frequently used information
that cannot be held in L1 cache
On the CPU board (Pentium Pro and
Pentium 2)
On the motherboard
Uses SRAM technology
Standard L2 Cache Sizes
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80486
80486DX4
Pentium
Pentium MMX
Pentium Pro
Pentium 2
Celeron
Pentium 3
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0KB
0KB
0KB
0KB
256KB
512KB
0KB
512KB
COAST Modules
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Some Pentium motherboards used L2
cache boards called COAST modules
Looked like a DIMM except they are
shorter and taller
Used Pipeline-Burst mode