2. RAM on the MotherboardRAM on the Motherboard
Loses all data when PC is turned offLoses all data when PC is turned off
(except data stored on CMOS chip)(except data stored on CMOS chip)
Two categoriesTwo categories
– Static RAM (SRAM)Static RAM (SRAM)
FastFast
Used as a memory cacheUsed as a memory cache
– Dynamic RAM (DRAM)Dynamic RAM (DRAM)
Slower; requires constant refreshingSlower; requires constant refreshing
8. Dynamic RAMDynamic RAM
TechnologiesTechnologies
Stored on DIMM, RIMM, or SIMMStored on DIMM, RIMM, or SIMM
modules (plug directly intomodules (plug directly into
motherboard)motherboard)
Differences among these modules:Differences among these modules:
– Width of data path that each typeWidth of data path that each type
accommodatesaccommodates
– The way data moves from system bus toThe way data moves from system bus to
module
12. DRAMDRAM
SIMM technologiesSIMM technologies
– Can use either EDO or FPM technologyCan use either EDO or FPM technology
DIMM technologiesDIMM technologies
– Can use either BEDO (burst EDO) orCan use either BEDO (burst EDO) or
synchronous RAM (SDRAM)synchronous RAM (SDRAM)
RIMM technologiesRIMM technologies
– Each socket must be filled to maintainEach socket must be filled to maintain
continuitycontinuity
15. Error Checking andError Checking and
ParityParity
ParityParity
– Error-checking procedure in which every byteError-checking procedure in which every byte
has an even number of ones or an oddhas an even number of ones or an odd
number of onesnumber of ones
– Older method of testing integrity of bitsOlder method of testing integrity of bits
Stored in RAM or secondary mediumStored in RAM or secondary medium
Sent over a communications deviceSent over a communications device
Error-correcting code (ECC)Error-correcting code (ECC)
– Current method of error checking that canCurrent method of error checking that can
detect and correct an error in a single bitdetect and correct an error in a single bit
17. Other Memory FeaturesOther Memory Features
CAS (column access strobe) latencyCAS (column access strobe) latency
RAS (row access strobe) latencyRAS (row access strobe) latency
Both CAS and RAS refer to theBoth CAS and RAS refer to the
number of clock cycles it takes to writenumber of clock cycles it takes to write
or read a column or row of dataor read a column or row of data
18. Memory Speeds: FactorsMemory Speeds: Factors
to Considerto Consider
Speed of memory in ns, MHz, or PC ratingSpeed of memory in ns, MHz, or PC rating
How much memory is installedHow much memory is installed
Memory technology usedMemory technology used
CL (CAS Latency) ratingCL (CAS Latency) rating
ECC/parity or non-ECC/nonparityECC/parity or non-ECC/nonparity
CL- the number of clock cycles between the time a read command is
sent and the data is available
20. Upgrading MemoryUpgrading Memory
What to look for when buying memoryWhat to look for when buying memory
chips and moduleschips and modules
How much and what kind of memoryHow much and what kind of memory
to buyto buy
Reading ads about memory modulesReading ads about memory modules
Installing memoryInstalling memory
21. What to Look for WhenWhat to Look for When
Buying Memory ChipsBuying Memory Chips
and Modulesand Modules
Use type, size, density, and fastestUse type, size, density, and fastest
speed supported by the motherboardspeed supported by the motherboard
Match tin leads to tin connectors andMatch tin leads to tin connectors and
gold leads to gold connectorsgold leads to gold connectors
Beware of remanufactured and re-Beware of remanufactured and re-
marked memory chipsmarked memory chips
22. How Much and WhatHow Much and What
Kind of Memory to BuyKind of Memory to Buy
Determine how much memory youDetermine how much memory you
have and needhave and need
Identify the number, type, and size ofIdentify the number, type, and size of
memory modules supported by yourmemory modules supported by your
motherboardmotherboard
Determine how much memory can youDetermine how much memory can you
affordafford
26. Installing MemoryInstalling Memory
Protect chips against static electricityProtect chips against static electricity
Usually modules pop into place easilyUsually modules pop into place easily
and are secured by spring catches onand are secured by spring catches on
both endsboth ends
31. Types of RAM
SDRAM
– Systems use some form of synchronous
DRAM (SDRAM)
Still DRAM, but it is synchronous
– SDRAM DIMMs came in a wide variety of
pin sizes
Desktops were the 168-pin variety.
Laptop DIMMs came in 68-pin, 144-pin
32. RDRAM
Replace SDRAM with a very fast, new
type of RAM developed byRambus,
Inc. called Rambus DRAM, or simply
RDRAM
Came in two sizes:
– A 184-pin for desktops
– A 160-pin SO-RIMM for laptops
33. DDR SDRAM
Double Data Rate SDRAM (DDR
SDRAM)
DDR SDRAM for desktops comes in 184-
pin DIMMs
DDR SDRAM for laptopscomes in either
200-pin SO-DIMMs or 172-pin micro-
DIMMs
34. DDR2
Run at a blistering PC4800.
4.8 gigabytes per second (GBps) of
data throughput
DDR2 uses a 240-pin DIMM that’s not
compatible with DDR
35. Latency
A delay in RAM’s response time is
called its LatencyLatency
RAM with a lower latency such as CL2
is faster than RAM with a higher
latency such as CL3 because it
responds more quickly
