RAM is the computer's temporary memory that is erased when the power is turned off. There are two main types of RAM - static RAM (SRAM) which is fast but expensive, and dynamic RAM (DRAM) which is slower but cheaper. DRAM needs to be regularly refreshed to prevent data loss. RAM modules like SIMMs, DIMMs, and RIMMs directly plug into the motherboard and come in different widths and data transfer speeds. Factors like RAM type, amount installed, and latency specifications determine overall memory performance.

1. RAM

2. RAM on the Motherboard
 Loses all data when PC is turned off
(except data stored on CMOS chip)
 Two categories
– Static RAM (SRAM)
 Fast
 Used as a memory cache
– Dynamic RAM (DRAM)
 Slower; requires constant refreshing

3. DRAM

4. SRAM

5. Memory Technologies

6. How SRAM Is Used in
Different Memory Caches

7. How Memory Caching
Works

8. Dynamic RAM
Technologies
 Stored on DIMM, RIMM, or SIMM
modules (plug directly into
motherboard)
 Differences among these modules:
– Width of data path that each type
accommodates
– The way data moves from system bus to
module

9. Examples of Memory
Modules

10. DRAM Technologies

11. DRAM Technologies
(continued)

12. DRAM
 SIMM technologies
– Can use either EDO or FPM technology
 DIMM technologies
– Can use either BEDO (burst EDO) or
synchronous RAM (SDRAM)
 RIMM technologies
– Each socket must be filled to maintain
continuity

13. Identifying the DIMM
Module

14. RIMM Technologies

15. Error Checking and Parity
 Parity
– Error-checking procedure in which every byte
has an even number of ones or an odd
number of ones
– Older method of testing integrity of bits
 Stored in RAM or secondary medium
 Sent over a communications device
 Error-correcting code (ECC)
– Current method of error checking that can
detect and correct an error in a single bit

16. Parity

17. Other Memory Features
 CAS (column access strobe) latency
 RAS (row access strobe) latency
 Both CAS and RAS refer to the number
of clock cycles it takes to write or read
a column or row of data

18. Memory Speeds: Factors
to Consider
 Speed of memory in ns, MHz, or PC rating
 How much memory is installed
 Memory technology used
 CL (CAS Latency) rating
CL- the number of clock cycles between the time a read command is
sent and the data is available
 ECC/parity or non-ECC/nonparity

19. Factors That Contribute
to Memory Speed

20. Upgrading Memory
 What to look for when buying memory
chips and modules
 How much and what kind of memory
to buy
 Reading ads about memory modules
 Installing memory

21. What to Look for When
Buying Memory Chips and
Modules
 Use type, size, density, and fastest
speed supported by the motherboard
 Match tin leads to tin connectors and
gold leads to gold connectors
 Beware of remanufactured and re-marked
memory chips

22. How Much and What Kind
of Memory to Buy
 Determine how much memory you
have and need
 Identify the number, type, and size of
memory modules supported by your
motherboard
 Determine how much memory can you
afford

23. Using Motherboard
Documentation to Select
Memory

24. Using Motherboard
Documentation to Select
Memory (continued)

25. RDRAM Memory
Configuration

26. Installing Memory
 Protect chips against static electricity
 Usually modules pop into place easily
and are secured by spring catches on
both ends

27. Installing a SIMM Module

28. Installing a DIMM Module

29. Installing a DIMM Module
(continued)

30. Installing a RIMM Module

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 Latency
 RAM with a lower latency such as CL2
is faster than RAM with a higher
latency such as CL3 because it
responds more quickly