1. Chapter 3 Memory

2. Chapter 3 Objectives Define memory Define memory Determine how memory is measured Determine how memory is measured Differentiate between the various types of memory Differentiate between the various types of memory Define RAM Define RAM Define cache memory Define cache memory

3. MemoryMemory What is memory? operating system and other system software that control the usage of the computer equipment application programs that carry out a specific task data being processed by application programs b Three basic items stored in memory b Temporary storage place for data, instructions, and information b Consists of one or more chips on the motherboard or some other circuit board

4. MemoryMemory Bytes are the basic storage unit in memory Bytes are the basic storage unit in memory Each byte is stored at a specific location in memory called an address Each byte is stored at a specific location in memory called an address How are bytes stored? b Each address has a unique identifying number, like the seats on an airplane seat C22seat B22seat A22 b Each address can hold only a single byte b Each address can be full or empty

5. MemoryMemory How is memory measured? Size of memory is measured by the number of bytes available b Kilobyte - 1,024 bytes b Megabyte - about one million bytes

6. Volatile Memory Loses its contents when the computer's power is turned off volatile memoryMemoryMemory What are the two types of memory in the system unit? nonvolatile memory

7. MemoryMemory Memory chips that can be read from and written to by the processor and other devices When the computer starts, operating system files are loaded from a hard disk into RAM What is random access memory (RAM)? As additional programs and data are requested, they also load from storage into RAM Most RAM is volatile

8. Storage (hard disk) RAM Step 3: When you quit Word, RAM may be used to store another program or data. The program is removed from the screen and the operating system’s user interface redisplays. Step 1: When your computer is running, certain operating system files are in RAM. Shown here is the operating system’s user interface. Step 2: When you start a word processing program such as Word, the program loads into RAM from a hard disk. As you create a document, it is in RAM and displays on your screen. Step 4: When you start a spreadsheet program such as Excel, the program loads into RAM from a hard disk. As you create a spreadsheet, it is in RAM and displays on your screen.MemoryMemory How are applications transferred in and out of RAM? Step 5: When you quit Excel, RAM may be used to store another program or data. Excel is removed from your screen and the operating system’s user interface redisplays.

9. MemoryMemory What are the two basic types of RAM chips? Dynamic RAM (DRAM) b Also called main memory b Most common type Static RAM (SRAM) b Used for special applications such as cache b Faster and more reliable b is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM (DRAM), it does not need to be periodically refreshed Synchronous DRAM (SDRAM) Double data rate SDRAM (DDR SDRAM or SDRAM II) Direct Rambus ® DRAM (Direct RDRAM ® ) Variations:

10. MemoryMemory What is a memory module? single inline memory modules (SIMMs) Rambus ® inline memory module (RIMM) b Small circuit board with RAM chips, which are smaller in size than processor chips b Inserts into the motherboard b Three types: SIMMS, DIMMS, and RIMMS dual inline memory modules (DIMMs)

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

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

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

14. DRAM - Dynamic RAM In DRAM a transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. In DRAM a transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. A DRAM chip have data lines: one chip might handle 8-bit-wide data, another 16-bit-wide data. A DRAM chip have data lines: one chip might handle 8-bit-wide data, another 16-bit-wide data. It also has address lines It also has address lines Tech’s describe chips by bits rather than byte (ex x8, x16) Tech’s describe chips by bits rather than byte (ex x8, x16) An individual DRAM chip that holds 1,048,576 rows and 8 columns, for ex., would be a 1 Mx8 chip. An individual DRAM chip that holds 1,048,576 rows and 8 columns, for ex., would be a 1 Mx8 chip.

15. Organizing DRAM The original 8088 processor had an 8-bit frontside bus. All the commands given to an 8088 were in 8-bit chuncks. So a RAM is needed that could store data in 8-bit (1-byte) chunck. The original 8088 processor had an 8-bit frontside bus. All the commands given to an 8088 were in 8-bit chuncks. So a RAM is needed that could store data in 8-bit (1-byte) chunck. Today’s DRAM chips may have widths greater than 1 bit, but back in the old days, all DRAM chips were 1 bit wide. i.e. you only had sizes like 64 Kx1, so eight 1-bit chips are electronically organized with memory controller chip to be eight wide. They look like a single 8-bit-wide DRAM chip to CPU. Today’s DRAM chips may have widths greater than 1 bit, but back in the old days, all DRAM chips were 1 bit wide. i.e. you only had sizes like 64 Kx1, so eight 1-bit chips are electronically organized with memory controller chip to be eight wide. They look like a single 8-bit-wide DRAM chip to CPU.

16. Practical RAM How did 8088 handled 2-byte commands? It took the command 1 byte at a time. it took twice as long to handle the command because the MCC had to go to RAM twice. How did 8088 handled 2-byte commands? It took the command 1 byte at a time. it took twice as long to handle the command because the MCC had to go to RAM twice. 8086 had 16-bit frontside bus. RAM and MCC are changed accordingly. 8086 had 16-bit frontside bus. RAM and MCC are changed accordingly.

17. Bus Review Address Bus Address Bus This addresses the RAM This addresses the RAM Number of lines in address bus determines max RAM (32 lines = 4 GB, 36 lines = 64 GB) Number of lines in address bus determines max RAM (32 lines = 4 GB, 36 lines = 64 GB) External Data Bus External Data Bus This is where data is placed once addressed This is where data is placed once addressed MCC retrieves data from RAM then places on EDB MCC retrieves data from RAM then places on EDB Width of data bus dictates width of RAM Width of data bus dictates width of RAM Frontside Bus Frontside Bus Same as External Data Bus Same as External Data Bus Backside Bus Backside Bus Used to access cache Used to access cache

18. MemoryMemory What is a memory module (memory stick)? dual inline memory module (DIMM) memory chip b RAM chips usually reside on a small circuit board which inserts into motherboard

19. DRAM sticks As CPU data bus sizes increased, so too the need for RAM wide enough to fill the bus. Intel 80386 CPU for ex, had a 32-bit data bus and thus the need for 32- bit wide DRAM. It is waste of space to line up 32 1- bit-wide DRAM chips on a motherboard. As CPU data bus sizes increased, so too the need for RAM wide enough to fill the bus. Intel 80386 CPU for ex, had a 32-bit data bus and thus the need for 32- bit wide DRAM. It is waste of space to line up 32 1- bit-wide DRAM chips on a motherboard. Wider DRAM chips were created, ex: x4, x8, and x16 (modern chips come in x32, x64) and multiples of them were put on a small circuit board called a stick or module. Wider DRAM chips were created, ex: x4, x8, and x16 (modern chips come in x32, x64) and multiples of them were put on a small circuit board called a stick or module. Ex: A 512-MB stick of RAM means that the total capacity of RAM is 512 Mega bytes Ex: A 512-MB stick of RAM means that the total capacity of RAM is 512 Mega bytes Exercise: what is the difference between DRAM width and module width? Exercise: what is the difference between DRAM width and module width?

20. DRAM sticks The fig. shown is an early stick called Single Inline Memory Module (SIMM) with 8 DRAM chips. The fig. shown is an early stick called Single Inline Memory Module (SIMM) with 8 DRAM chips. To add RAM to a modern machine means to get the right stick(s) for the particular motherboard. To add RAM to a modern machine means to get the right stick(s) for the particular motherboard. Exercise: how to know what sort of module you need and how much RAM you can install? Exercise: how to know what sort of module you need and how much RAM you can install? Modern CPUs have commands that are up to 64 bits wide. They also have at least 64-bit front side bus. The modern MCC provides at least 64 bits of data at a time (some MCCs are 128 bits wide) Modern CPUs have commands that are up to 64 bits wide. They also have at least 64-bit front side bus. The modern MCC provides at least 64 bits of data at a time (some MCCs are 128 bits wide)

21. RAM Modules RAM memory chips are sold in modules. RAM memory chips are sold in modules. 5 modern types 5 modern types SIMM DIMM SODIMM RIMM SORIMM

22. SIMMs (Single Inline Memory Module) Inserted into SIMM socket on motherboard Inserted into SIMM socket on motherboard SIMMs come in both 30-pin and 72-pin versions (30 or 72 pin connector) SIMMs come in both 30-pin and 72-pin versions (30 or 72 pin connector) The 30-pin SIMM is an 8-bit chip, with 1 optional parity bit The 30-pin SIMM is an 8-bit chip, with 1 optional parity bit The 72-pin SIMM is a 32-bit chip, with 4 optional parity bits. It is inch longer than 30 pin SIMM The 72-pin SIMM is a 32-bit chip, with 4 optional parity bits. It is inch longer than 30 pin SIMM Notch in the middle of the pins Notch in the middle of the pins

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

24. Calculating the number of memory modules you must install to create one full bank Determine the data bus width of the processor for ex( 64 bits) Determine the data bus width of the processor for ex( 64 bits) Determine the bit width of the memory module for ex (32 bits). Determine the bit width of the memory module for ex (32 bits). Divide the data bus width of the processor by the bit width of the memory module, you will get 2 is the number of memory modules you must install to create one full bank Divide the data bus width of the processor by the bit width of the memory module, you will get 2 is the number of memory modules you must install to create one full bank

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

26. Common Sizes: 72 pin SIMM 1x32 = 4MB 1x32 = 4MB 1x36 = 4MB parity 1x36 = 4MB parity 2x32 = 8MB 2x32 = 8MB 2x36 = 8MB parity 2x36 = 8MB parity 4x32 = 16MB 4x32 = 16MB 4x36 = 16MB parity 4x36 = 16MB parity Ex: 1x32 means 1Mega x 32 bit Ex: 1x32 means 1Mega x 32 bit 8x32 = 32MB 8x36 = 32MB parity 16x32 = 64MB 16x36 = 64MB parity Need two sticks for a bank on Pentium 64 bit bus

27. DIMM DIMM Dual In Line Memory Module Dual In Line Memory Module All DIMMs are 64 bit All DIMMs are 64 bit 168-pin used for DRAM and SDRAM 168-pin used for DRAM and SDRAM 184-pin used for DDR RAM 184-pin used for DDR RAM Capacity of 8MB to 1GB per module Capacity of 8MB to 1GB per module Has a secondary keying notch so they'll only fit into their slots one way. Has a secondary keying notch so they'll only fit into their slots one way.

28. Common Sizes for DIMM 1x64 = 8MB 1x64 = 8MB 2x64 = 16MB 2x64 = 16MB 4x64 = 32MB 4x64 = 32MB 8x64 = 64MB 8x64 = 64MB 16x64 = 128M 16x64 = 128M 32x64= ? (exercise) 32x64= ? (exercise)

29. SO-DIMM Small Outline Dual In Line Memory Module Small Outline Dual In Line Memory Module 72, 144, 200-pin 72, 144, 200-pin Used in laptops Used in laptops Physically smaller than standard DIMMs Physically smaller than standard DIMMs Installing SO-DIMM in laptops. Installing SO-DIMM in laptops.

30. RIMMs: Use Rambus Dynamic RAM (RDRAM) chips i.e. a stick of RDRAM is called a RIMM. Use Rambus Dynamic RAM (RDRAM) chips i.e. a stick of RDRAM is called a RIMM. 64-bit wide but the Rambus MCC alternates between 2 sticks to increase the speed of data retrieval. So it is required to install RIMMs in pairs to use this dual-channel architecture 64-bit wide but the Rambus MCC alternates between 2 sticks to increase the speed of data retrieval. So it is required to install RIMMs in pairs to use this dual-channel architecture RDRAM motherboards require that all RIMM slots be populated. Use CRIMM (Continuity RIMM) for unused pairs of slots. It enables RDRAM system to terminate properly RDRAM motherboards require that all RIMM slots be populated. Use CRIMM (Continuity RIMM) for unused pairs of slots. It enables RDRAM system to terminate properly sizes: 184-pin for desktops and 160-pin SO-RIMM for laptops. sizes: 184-pin for desktops and 160-pin SO-RIMM for laptops. Even so RIMM and DIMM have same basic size, You could not accidentally install a RIMM into a DIMM slot or vice versa. Even so RIMM and DIMM have same basic size, You could not accidentally install a RIMM into a DIMM slot or vice versa.

33. 184-pin DDR DIMM and RIMM

34. Types of RAM technologies Types of RAM technologies FPM RAM obsolete FPM RAM obsolete SDRAM SDRAM RDRAM RDRAM DDR SDRAM DDR SDRAM DDR2 SDRAM DDR2 SDRAM

35. SDRAM SDRAM SDRAM: Synchronous DRAM (DRAM is asynchronous). Tied to the system clock. SDRAM: Synchronous DRAM (DRAM is asynchronous). Tied to the system clock. The RAM speed had to match or exceed system speed or the computer would be ubstable or would not wok at all The RAM speed had to match or exceed system speed or the computer would be ubstable or would not wok at all (66, 75, 83, 100, 133) Mhz are the common SDRAM speeds in the early SDRAM systems. The speeds were prefixed with a “PC”, for ex: PC66, PC133. For a Pentium III computer with 100-MHz frontside bus, you needed to buy SDRAM DIMMs rated to handle it as PC100 or PC133 (66, 75, 83, 100, 133) Mhz are the common SDRAM speeds in the early SDRAM systems. The speeds were prefixed with a “PC”, for ex: PC66, PC133. For a Pentium III computer with 100-MHz frontside bus, you needed to buy SDRAM DIMMs rated to handle it as PC100 or PC133 Made on a DIMM stick in a wide variety of pin sizes. Made on a DIMM stick in a wide variety of pin sizes. Common size on desktops: 168-pin DIMM Common size on desktops: 168-pin DIMM Laptop DIMM: 68-pin,… Laptop DIMM: 68-pin,… Laptop SODIMM: 72-pin,... Laptop SODIMM: 72-pin,...

36. SDRAM When the CPU is ready to access data from memory, it goes to a specified clock point. The CPU knows when operations are going to be completed and when data is going to be available. No wait states means better performance. When the CPU is ready to access data from memory, it goes to a specified clock point. The CPU knows when operations are going to be completed and when data is going to be available. No wait states means better performance.

37. RDRAM: Rambus Dynamic RAM SDRAM could not be fast enough to handle quad- pumped 400-Mhz frontside bus.  RDRAM developed by Rambus Inc. SDRAM could not be fast enough to handle quad- pumped 400-Mhz frontside bus.  RDRAM developed by Rambus Inc. Used for Pentium 4 Used for Pentium 4 RDRAM had a speeding rate 600, 700, 800 and 1066 MHz versions RDRAM had a speeding rate 600, 700, 800 and 1066 MHz versions RDRAM employed dual-channel architecture RDRAM employed dual-channel architecture A stick of RDRAM is called RIMM A stick of RDRAM is called RIMM 184-pin RIMM, 160-pin SO-RIMM for laptops 184-pin RIMM, 160-pin SO-RIMM for laptops

38. RDRAM Became obsolete: Became obsolete: - technology was owned wholly by Rambus. - Expense (it costs more than SDRAM) - RDRAM worked only on Pentium 4 (closed deal with the technology)

39. DDR SDRAM: Double data rate synchronous dynamic RAM DDR RAM was developed from SDRAM technology DDR RAM was developed from SDRAM technology It doubles the throughput of SDRAM by making 2 processes for every clock cycle. It doubles the throughput of SDRAM by making 2 processes for every clock cycle. Runs at 200, 266, 333 …. 600 MHz Runs at 200, 266, 333 …. 600 MHz DDR RAM uses 184-pin DIMMs that are different from SDRAM DIMMs. They will not fit in the same socket. DDR RAM uses 184-pin DIMMs that are different from SDRAM DIMMs. They will not fit in the same socket.

40. DDR SDRAM Example: Example: A Pentium PC has a 64 bit external data bus. 64 bits = 8 bytes. With a 100 Mhz motherboard clock, the DDR chip runs at 200 Mhz. (2 processes/clock cycle)  DDR200 A Pentium PC has a 64 bit external data bus. 64 bits = 8 bytes. With a 100 Mhz motherboard clock, the DDR chip runs at 200 Mhz. (2 processes/clock cycle)  DDR200 The processor can access 200 x 8 (the width of all DDR SDRAM) = 1600 M bytes/second  PC1600 The processor can access 200 x 8 (the width of all DDR SDRAM) = 1600 M bytes/second  PC1600

41. DDR II DDR-II extends DDR with some improvements in its electrical characteristics so as to run faster with less power DDR-II extends DDR with some improvements in its electrical characteristics so as to run faster with less power The speed comes by clock doubling the input/output circuits on the chips. This does not speed up the core RAM that holds data. The speed comes by clock doubling the input/output circuits on the chips. This does not speed up the core RAM that holds data. 240-pin DIMM 240-pin DIMM Ex Ex Core RAM DDR I/O DDR2 speed PC speed Clock speed speed rating rating 100 Mhz 200 Mhz DDR2-400 PC3200 100 Mhz 200 Mhz DDR2-400 PC3200 133 Mhz 266 Mhz DDR2-532 PC4200 133 Mhz 266 Mhz DDR2-532 PC4200 250 Mhz 500 Mhz DDR2-1000 PC8000 250 Mhz 500 Mhz DDR2-1000 PC8000

42. Double sided DIMMs Single sided sticks have chips on one side (bank) of the stick. Single sided sticks have chips on one side (bank) of the stick. Double sided sticks have chips on both sides (two banks). Double sided sticks have chips on both sides (two banks). Some motherboards can’t use Double sided sticks or can only use them in certain ways. Some motherboards can’t use Double sided sticks or can only use them in certain ways.

43. Memory latency The delay in RAM’s response time The delay in RAM’s response time RAM with a lower latency –such as CL2- is faster than RAM with a higher latency –such as CL3- RAM with a lower latency –such as CL2- is faster than RAM with a higher latency –such as CL3- If you speed up the system clock, the stick might take an extra click before it can respond If you speed up the system clock, the stick might take an extra click before it can respond Exercise: how motherboard enable you to adjust RAM timing? Exercise: how motherboard enable you to adjust RAM timing?

44. Parity and ECC It is possible that a RAM chip give bad data to the memory controller ( 1  0 or 0  1) It is possible that a RAM chip give bad data to the memory controller ( 1  0 or 0  1) Parity RAM: first type of error-detecting RAM. It stores an extra bit of data (called parity bit) that the MCC used to verify if the data was correct. Not all errors are detected by parity and no correction occurs Parity RAM: first type of error-detecting RAM. It stores an extra bit of data (called parity bit) that the MCC used to verify if the data was correct. Not all errors are detected by parity and no correction occurs Each time data is placed in RAM parity bit is set Each time data is placed in RAM parity bit is set Each time you access data in RAM, parity bit is checked Each time you access data in RAM, parity bit is checked Parity is usually implemented by adding an extra chip on the memory module that is one bit wide and as deep as all the other chips in the module Parity is usually implemented by adding an extra chip on the memory module that is one bit wide and as deep as all the other chips in the module

45. ECC (Error Correction Code) RAM A special type of RAM A special type of RAM ECC detects a single bit is incorrect. It fixes the error on the fly and correct it ECC detects a single bit is incorrect. It fixes the error on the fly and correct it ECC requires more bits for each byte. ECC requires more bits for each byte. 90% of data errors are single-bit errors, ECC does a very good job. 90% of data errors are single-bit errors, ECC does a very good job. Can detect multiple bit errors but cannot correct them. Can detect multiple bit errors but cannot correct them. ECC costs a lot more, because of the additional number of bits. It is also slower than non-ECC RAM. ECC costs a lot more, because of the additional number of bits. It is also slower than non-ECC RAM. ECC RAMs comes in every DIMM package type ECC RAMs comes in every DIMM package type It needs a motherboard with an MCC designed to use ECC. It needs a motherboard with an MCC designed to use ECC. Only expensive motherboard for high-end systems use ECC. Only expensive motherboard for high-end systems use ECC.

46. b Software package usually indicates how much RAM is requiredMemoryMemory b The more RAM, the more programs and files a computer can work on at once How much RAM is needed?

47. MemoryMemory b Necessary RAM depends on what type of applications you intend to run on your computer

48. Does adding more RAM to your computer make it faster? adding RAM will normally cause your computer to seem faster on certain types of operations. adding RAM will normally cause your computer to seem faster on certain types of operations. When you run a program such as a word processor or an Internet browser, the microprocessor in your computer pulls the executable file (.exe) off the hard disk and loads it into RAM. When you run a program such as a word processor or an Internet browser, the microprocessor in your computer pulls the executable file (.exe) off the hard disk and loads it into RAM.microprocessor Then the microprocessor loads in the data files at which you want to look, which might total several megabytes if you are looking at more than one document or browsing a page with a lot of graphics. Then the microprocessor loads in the data files at which you want to look, which might total several megabytes if you are looking at more than one document or browsing a page with a lot of graphics. Besides all of those applications, the operating system itself is taking up a good bit of space. Besides all of those applications, the operating system itself is taking up a good bit of space.

49. Do You Need RAM? Two symptoms point to needing more RAM Two symptoms point to needing more RAM General system sluggishness Especially as more programs are opened General system sluggishness Especially as more programs are opened Disk thrashing or excessive hard drive accessing Caused by excessive paging Disk thrashing or excessive hard drive accessing Caused by excessive paging Note: Disk thrashing can also be caused by disk fragmentation Note: Disk thrashing can also be caused by disk fragmentation

50. Paging File Data can be moved between physical RAM and Virtual RAM Data can be moved between physical RAM and Virtual RAM Data swapped in 64K page blocks Data swapped in 64K page blocks Too much too often causes disk thrashing Too much too often causes disk thrashing Physical RAM OS Word Browser Email Disk Drive Game

51. MemoryMemory What is memory cache? b Also called cache store or RAM cache b Helps speed the processes of the computer by storing frequently used instructions and data b When the processor needs an instruction or data, it first searches cache. If it cannot locate the item in cache, then it searches RAM.

52. MemoryMemory What are the three types of cache? Not used on older computers Level 3 (L3) Only on newer computers with L2 advanced transfer cache Cache on motherboard External cache Much larger capacity, but slower Level 2 (L2) On older computers High-speed SRAM chips on motherboard On newer computers Advanced transfer cache built directly on the processor chip Primary or internal cache Built directly into the processor chip Small capacity Level 1 (L1)

53. MemoryMemory What is read-only memory (ROM)? BIOS (basic input/output system) Stored on ROM Sequence of instructions the computer follows to load the operating system and other files when you first turn on the computer Nonvolatile — Contents not lost when the computer is turned off b Memory chips that contain data, instructions, or information that is recorded permanently Data can only be read, cannot be modified

54. MemoryMemory What are types of ROM? PROM (programmable read-only memory) Blank ROM on which you can place items permanently Firmware ROM chips manufactured with permanently written data, instructions, or information EEPROM (electrically erasable programmable read- only memory) A type of PROM containing microcode that a programmer can erase

55. MemoryMemory What is flash memory? b Also called flash ROM or flash RAM b Nonvolatile memory that can be erased electronically and reprogrammed b Stores data and programs on many handheld computers and devices b Flash memory cards store flash memory on removable devices instead of chips

56. Quiz Match: Match: SIMM- DIMM-RIMM-CRIMM 1. SDRAM…………… 2. RDRAM…………… 3. DDR SDRAM……….. 4. DDR2 …………..