V2012.13
Agenda
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Old Business
New Business
Week ‘2’ Meeting Review
Week 3 Topics:
– Intro to Memory
– Continue to trouble shoot our PC
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Old Business
• Sub-groups
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Graphics
Web Design
App Development
Other?
Scorer’s table job
Email me with interest!
Fundraising
Remember … participate!
– Read email, polls, requests, etc.
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New Business
• District Tech Department Help
– Install Office 2010
– Repair Computers
• Contact Info
– Request your name/year
• Comments on Twitter
• T-Shirts
– Limited sizes/colors
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Week 2 Meeting Review
• Intro to Computer Repair
– What did you think?
– Any follow-up questions?
• Our non-working PC …
– Did you answer the poll question?
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Intro to Memory
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Intro to Memory
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Common Terms
Common Types
How it works
Resources
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First, Some Common Terms
Term
Definition
Purpose
Volatile
Computer memory that requires
power to maintain the stored
information
RAM
Non-Volatile Computer memory that can
retain the stored information
even when not powered
ROM
DIMM
Difference between SIMMs and DIMMs
is that DIMMs have separate electrical
contacts on each side of the module
Dual in-line memory module
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Common Types of Memory
Type
Definition
Purpose
BIOS
Basic Input/Output System
Boots firmware, POST
ROM
Read-only memory
Used to store firmware
Cache
Smaller, faster memory
Reduce average time to access
main memory (L1, L2, L3)
RAM
Random-access memory
Data accessed quickly in random
order, in same amount of time
DRAM
Dynamic random-access memory
Data fades unless the capacitor
charge is refreshed, very high
densities
SRAM
Static random-access memory
Holds charge, typically faster, less
dense, more expensive
SDRAM/DDR
Synchronous dynamic randomaccess memory
Synchronized with the computer's
system bus (DDR1, DDR2, DDR3)
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DDR (SDRAM) Memory
• Double Data Rate
• Two data transfers
per cycle
• Higher bandwidth
– DDR3 has the ability
to transfer data at
twice the rate of DDR2
• Uses less power
(30%)
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Common Types of Memory
Type
Definition
Purpose
Flash
Non-volatile computer storage
chip that can be erased and
reprogrammed
Used in USB drives, memory cards,
solid-state drives
SGRAM/GDDR
Synchronous graphics randomaccess memory, Graphics Double
Data Rate
Specialized form of SDRAM for
graphics adaptors (GDDR3, GDDR4,
GDDR5)
Solid State/SSD
Solid-state drive, no moving
mechanical components, retains
data without power
Data storage device
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DDR vs GDDR
• GDDR is built for much higher bandwidth, thanks
to a wider memory bus
• GDDR has lower power and heat dispersal
requirements compared to DDR, allowing for
higher performance modules, with simpler
cooling systems
• DDR1, DDR2, and DDR3 have a 64 bit bus (or
128 bit in dual channel). GDDR3, comparatively,
commonly uses between a 256 bit bus and 512
bit bus, or interface (across 4-8 channels)
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DRAM vs SSDs
• DRAM is used to run stuff
• SSDs are where you store stuff
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Memory Hierarchy
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Memory Hierarchy
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Why so many types of memory?
• Different pieces of a computer system have
different requirements for speed, size and cost
• Computer designers have solved the cost
problem by "tiering" memory
• Using expensive memory in small quantities and
then backing it up with larger quantities of less
expensive memory
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So, how does memory work?
• The basics …
• Each memory ‘cell’ is comprised of:
– Transistor
– Capacitor
• Each cell can hold 1 bit of information
• Cell contains a data input line, a data output line,
a Read/Write line and a select line
– The select line activates the cell and Read/Write line
tells it either to output its contents or store what is at
its input
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So, how does memory work?
• Cells are organized in a grid pattern, rows
columns
• Data (‘line’) inputs and outputs for each cell are
connected together to form an ‘array’
• Data is written to a specific row and column of
the array, defined as the ‘binary address’
• CPU can access the data from that specific
address
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So, how does memory work?
• Data lines from multiple memory chips are
grouped to form a ‘data bus’
• Data bus has the following characteristics:
– Bus width refers to the number of bits that can be
sent to the CPU simultaneously
– Bus speed refers to the number of times a group of
bits can be sent each second
– Bus cycle occurs every time data travels from
memory to the CPU
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So, how does memory work?
• Memory Controller
– Manages the flow of data going to and from the main
memory
– Contain logic necessary to read and write to DRAM,
and to "refresh" the DRAM
– It can be a separate chip or integrated into another
chip (like the CPU)
– Part of the ‘Northbridge’
• Located closest to the CPU (or on the CPU) and controls the
fastest components on the motherboard: the CPU, video card
slot and RAM
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When/Why would you install memory?
• To improve performance
– O/S, apps getting larger
• To prevent disk ‘swapping’
– Windows creates ‘virtual RAM’
– In the form of ‘pagefile.sys’ on your hard drive
• But there are other factors that impact
performance …
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Summary
• Different types of memory address different
needs
• Used in almost every phase of a computer
system
• At a high level, memory is comprised of cells,
arrays, data bus
• Operated by a memory controller which
communicates with the CPU
• Generally helps improve performance
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Questions/Comments?
Scott Seighman
scotts@ahstechcrew.org
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Troubleshooting
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Our Non-Working PC …
• Dell 2400
• No output to screen
• Blinking amber light (power)
• Fans are not spinning
• What would you do next?
• Ideas …?
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