1. RAM
Chapter 1 part 4

2. Overview In this chapter, you will learn how to
Identify the different types of RAM packaging
Explain the varieties of DRAM
Install RAM properly
Perform basic RAM troubleshooting
Instructor Tip
When gaining attention and establishing common ground, ask questions such as, “What is RAM?” or “Who here has ever installed RAM?”
For a positive statement, tell the class, “In this lesson, we are going to learn how to recognize various forms of RAM, how RAM works, and how to install it properly.”

3. DRAM

4. DRAM
DRAM (dynamic random access memory) is the most popular type of electronic memory
Special type of semiconductor that stores ones and zeroes using microscopic capacitors and transistors
Single chip can hold millions of these capacitor/transistor combinations
Note: We tend to interchange the terms RAM and DRAM. Just be aware that DRAM is really a type of RAM. Most PCs use DRAM, so when we refer to the RAM we are usually talking about DRAM. When we refer to DRAM, we are talking about RAM.

5. Program Execution
Program code is copied from your hard disk into RAM before it is executed

6. Organizing DRAM DRAM is considered the standard
Low cost, high speed, and able to store data in a relatively small package
Many varieties of DRAM
DRAM stores programs and data in 8-bit (1-byte) chunks of memory
Chips have historically been referenced with respect to their depth and width
1 MB x 4
256 K x 1

7. Organizing DRAM The depth and width are measured in units of bits
Not easy to determine based on what’s written on chips
The physical size and the internal organization of the chip are not directly related

8. Review: Memory Controller Chip
The memory controller chip (MCC) device facilitates the flow of data from the RAM to the CPU
Data is placed on the external data bus
Width of data bus related to width or DRAM
MCC

9. Practical DRAM 8086 used 16-bit data bus
Much more expensive at the time
At $12,000 per PC, would not have fueled the PC revolution
Original 8088 chip used 8-bit data bus
Market was ready for this
Adapted to some commands needing 16 bits

10. Bus Review Address bus External data bus Frontside bus Backside bus
This addresses the RAM
Number of lines in address bus determines max RAM (32 lines = 4 GB, 36 lines = 64 GB)
External data bus
This is where data is placed once addressed
MCC retrieves data from RAM on places on EDB
Width of data bus dictates width of RAM
Frontside bus
Same as external data bus
Backside bus
Used to access cache
For many students, “buses” tend to run together. Expect the question: “What’s the difference between the address bus, the external data bus, and the frontside bus? If you’re unable to coax the question out of them, look for an opportunity to provide the clarification.
Address bus This is what addresses memory. Like a house has an address, memory has an address. We can store bytes of data in different addresses. The more address lines we have on the address bus, the more bytes of data we can store.
External data bus This is where the data is passed back and forth between CPU and memory (via the MCC).
Frontside bus With the advent of cache onboard the chip and accessed directly from the CPU (also known as the backside bus), the external data bus is now known as the frontside bus.

11. DRAM Sticks

12. 72-pin SIMMs A better solution was needed 72-pin SIMMs
Modern CPUs have 64-bit external data buses
72-pin SIMMs have a notch in the middle
Each 72-pin SIMM is 32 bits wide (two required)

13. Banking
Combining the widths of DRAM to match the width of the external data bus is called banking
The number of sticks that make up a bank depends on the chipset, which in turn depends on the CPU’s external data bus size
EDB of 64 bits = 2 SIMMS 32 bits wide
EDB of 64 bits = 1 DIMM 64 bits wide

14. Consumer RAM RAM has widths larger than bytes
8 bits wide = byte
16 bits wide = word
32 bits wide = double word
However, still referred to in bytes
256 MB, 512 MB, 1 GB sticks

15. Essentials: Types of RAM
CompTIA A+ Essentials
Essentials: Types of RAM

16. DIMM (Dual Inline Memory Module)
The 168-pin DIMM is the most popular DRAM package in use today
Extra pins to handle functions such as buffering and ECC
144-pin SO-DIMMs (small outline) are used in laptops

17. SDRAM SDRAM (synchronous dynamic RAM) are tied to the system clocks
Synchronized with system clock
SDRAM is always a DIMM, but a DIMM isn’t always SDRAM
Wide number of pins
Small-outline DIMM (SO-DIIMM) used on laptops
Faster than DRAMs
What makes SDRAM faster?
Before SDRAM, the system had to send the signal to DRAM, wait a certain number of clicks (this number was rounded up just to be sure the data would be ready), and then access the RAM for the data. Using the system clock, the chipset now knows exactly when the data is ready, speeding up the process

18. RDRAM RDRAM (Rambus DRAM) is a new type of RAM Speeds of up to 800 MHz
Comes on sticks called RIMMs
184-pin for desktops and 160-pin SO-RIMM for laptops
All slots must be populated: unused slots must have a CRIMM (continuity RIMM)
Terminology
RDRAM, or Rambus DRAM, is also called RIMM sticks.
RDRAM speeds start with “PC” followed by the speed, so 800 MHz RDRAM is known as PC800 and 1066 MHz RDRAM is known as PC1066.

19. DDR SDRAM Double Data Rate
DDR SDRAM doubles the throughput of SDRAM
184-pin DIMM packages (desktops)
172-, 200-pin DIMM packages (laptops)
Wide range of speeds
Considered a standard today
Dual slots are blue, third slot is black

20. DDR Speeds PC Speed Rating = Clock Speed DDR Speed Rating
100 MHz
DDR200
PC1600
133 MHz
DDR266
PC2100
166 MHz
DDR333
PC2700
200 MHz
DDR400
PC3200
217 MHz
DDR433
PC3500
233 MHz
DDR466
PC3700
250 MHz
DDR500
PC4000
275 MHz
DDR550
PC4400
300 MHz
DDR600
PC4800
PC Speed Rating =
Clock speed × 2 × 8

21. Dual-Channel Architecture
Dual-channel architectures use two sticks of RAM together to increase throughput
Similar to RAMBUS
Works only if two sticks
Dual slots often blue
Third one often black
DUAL DDR has a few quirks such as this one:
Motherboards that use NVIDIA’s nForce2 chipset have three DDR SDRAM slots, but dual channel only works if you populate the two blue dual slots and leave the third black slot empty
While every PC uses DRAM in one of its many variations for their RAM, other forms of RAM are found in PCs with names like VRAM and SGRAM.

22. DDR2 SDRAM DDR SDRAM doubles the throughput of SDRAM
Doubled the clock, increasing buffering
Does not speed up core RAM, but just the I/O
240-pin DIMM (not compatible with DDR)

23. DDR2 Speeds PC Speed Rating = Clock Speed DDR I/O Speed
DDR Speed Rating
PC Speed Rating
100 MHz
200 MHz
DDR2-400
PC2-3200
133 MHz
266 MHz
DDR2-533
PC2-4200
166 MHz
333 MHz
DDR2-667
PC2-5300
400 MHz
DDR2-800
PC2-6400
250 MHz
500 MHz
DDR2-1000
PC2-8000
PC Speed Rating =
Clock speed × 2 × 2 × 8

24. Double-Sided DIMMS
Almost all sticks come as single-sided or double- sided
Beware of double-sided sticks
Some are thicker, which prevents populating all slots in some motherboards
You motherboard may or may not be able to accept them.

25. Latency Latency Measure of how slow RAM may be.
CL2 refers to low latency. Faster. It takes two clock cycles to get data.
CL3 refers to high latency. Slower. It takes three clock cycles to get data.
Often listed as CAS (column address strobe).

26. Parity and ECC
Parity is a rudimentary method of checking the data to see if errors exist
No error correction, just detection
ECC (error correction code) is a special type of RAM used by high-end systems
Major advance in error checking on DRAM
Can also correct many errors
RAM sticks of any size can use the ECC DRAM, but it is most common as 168-pin DIMMs
A motherboard must be designed to use ECC to take advantage of the ECC RAM
Tech Tip
Registered DRAM
Most servers and many high-end workstations sport a DRAM variant called registered DRAM that facilitates high-volume data flow in and out of RAM. Registered DRAM has logic circuits—quite logically named registers—that buffer control signals to synchronize with the system clock. This sort of RAM helps these systems keep track of the hugely complex data transfers and manage multiple sticks of RAM. Typical home and office PCs, in contrast, use unbuffered (meaning without registers) DRAM, optimizing for speed rather than perfect data transfers.

27. Buffered/Registered DRAM
Most motherboards support only four sticks of RAM
More sticks present unique challenges
To overcome output problems, sticks add a buffering chip
Acts as intermediary between RAM and MCC

28. Working with RAM
What’s wrong with this picture?

29. Working with RAM Avoid ESD damage
Don’t touch pins or connectors directly
RAM is highly susceptible to ESD damage.

30. Do You Need RAM? Two symptoms point to needing more RAM
General system sluggishness, especially as more programs are opened
Disk thrashing or excessive hard drive accessing, caused by excessive paging
Note: Disk thrashing can also be caused by disk fragmentation.
How do know if your disk is thrashing?
Observe the LED at work
Use FreeMeter (

31. Page File Data can be moved between physical RAM and virtual RAM
Data swapped in 64-K page blocks
Too much too often causes disk thrashing
Physical RAM
Disk drive
Game OS
Note that this is a simplistic representation. Entire programs aren’t swapped back and forth between memory and the hard drive. Instead, 64-K pages are swapped based on what the system predicts won’t be needed soon. The name page file is derived from the 64-K “pages.”
Word
Browser

32. System RAM Recommendations
Operating System
Reasonable Minimum
Solid Performance
Power User
Windows 2000
128 MB
256 MB
512 MB
Windows XP
1 GB
Windows Vista
2 GB
Actual minimum requirements are much lower
Usually leads to slower computer and unhappy user

33. Determining Current RAM
My Computer Properties
Windows key- Pause/Break key
Task Manager
Ctrl-Shift-Esc

34. Getting the Right RAM Identify capacity Identify empty slots
What can the motherboard handle (look at the manual)
Identify empty slots
If all slots filled, you’ll have to pull some out
For example, pull out 256-MB sticks to add 512-MB sticks
CPU-Z is a great tool to determine what you have
Also shows latency

35. Mixing and Matching
Mixing DRAM speeds can cause the system to lock up, leading to data corruption
You can use faster DRAM than the motherboard recommends, but you won’t see an increase in performance
You can put different speeds of DRAM in different banks as long as they are both faster than the speed specified
Discussion Point
RAM speeds
In general, it is not a good idea to mix speeds on your RAM sticks. While this practice may sometimes work on some motherboards, it is far from predictable or consistent. The results may vary from working fine to intermittent crashes. Sometimes you can use one speed in one bank and another speed in another bank, but it is best not to mix speeds in the same bank.
Although your system can use faster RAM than your motherboard needs (i.e., PC133 on a 100-MHz motherboard), you will not see any improvements over normal operations.

36. Installing DIMMs Swing the side tabs away from upright.
Push the DIMM down somewhat hard. The two tabs should move back into place

37. Memory Details Signal presence detect (SPD) The RAM count
Reports the size, speed, data width, and voltage of the installed RAM to the BIOS
Can be read from BIOS
CPU-Z shows SPD data
The RAM count
Part of Power On Self Test
Counts addressable RAM and reports it
Remember the subtle differences between counting in binary and decimal 512 MB does not equal 512 million exactly.

38. Installing SO-DIMMs in Laptops
Make sure the system is off
No AC connection
Remove all batteries
Remove the panel or lift the keyboard
Slide the pins into position and then snap the SO-DIMM down into the retaining clips
Exercise
RAM installation
Have the students install various RAM sticks in various systems. Again, and as always, reinforce proper ESD protection.
You can install the RAM improperly, such as by mismatching the RAM or ignoring banking rules, and ask the students to diagnose the problem.

39. IT Technician
CompTIA A+ Technician
Troubleshooting RAM

40. Memory Errors Appear as Real memory errors Phantom errors
Parity errors, ECC error messages, system lockups, page faults, and BSoD
Real memory errors
“Parity error at xxxxx”
If xxxxx is consistently the same, you have a bad RAM stick
Phantom errors
Random memory addresses
Due to power issues, dust, heat

41. Check the RAM
A halt before the RAM check could indicate improperly installed RAM

43. Testing RAM
Hardware RAM testing devices can be used to troubleshoot errors
An economical option is to replace the existing sticks with new ones
Memtest32 is a freeware tool that can be used to test RAM

44. Beyond A+
To get the graphics response needed, games need powerful video cards and video RAM
Watch video cards to see where RAM is headed