Memory
Internal storage areas in the computer The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.
Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.
Memory Manufacturers Corsair, Kingston, Rambus, Crucial, Samsung, PNY, Micron
Memory Terminology
Memory speed - measured in nanoseconds, this is the time to access data that is stored in memory
the lower the nanoseconds the faster the memory (2ns-80ns)
the lower the nanoseconds the faster the memory (2ns-80ns)
Parity - A simple error checking method use in memory correction
ECC-Error correction code use in memory correction for newer computers
Memory Banks - A socket where memory is installed Example 4 banks will have 8MB of memory each for a total of 32MB
There are several different types of memory:
240-pin DIMM----------------------------- DDR3 SDRAM
ROM or Read Only Memory, Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to. It is non-volatile which means once you turn off the computer the information is still there.
PROM, short for programmable read-only memory A PROM is a memory chip on which data can be written only once. Once a program has been written onto a PROM, it remains there forever. Unlike RAM, PROM's retain their contents when the computer is turned off. The difference between a PROM and a ROM (read-only memory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, you need a special device called a PROM programmer or PROM burner. The process of programming a PROM is sometimes called burning the PROM.
EPROM (erasable programmable read-only memory) is a special type of PROM that can be erased by exposing it to ultraviolet light. Once it is erased, it can be reprogrammed. An EEPROM is similar to a PROM, but requires only electricity to be erased.
EEPROM- Acronym for electrically erasable programmable read-only memory. Pronounced double-ee-prom or e-e-prom, an EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not as fast as RAM. EEPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster.
RAM (Random Access Memory) is a temporary (Volatile) storage area utilized by the CPU. Before a program can be ran the program is loaded into the memory which allows the CPU direct access to the program.
2 Types of RAM
SRAM Short for static random access memory, and pronounced ess-ram. SRAM is a type of memory that is faster and more reliable than the more common DRAM (dynamic RAM). The term static is derived from the fact that it doesn't need to be refreshed like dynamic RAM.
SRAM is often used only as a memory cache usually found in the CPU (L1, L2 and L3 Cache)
DRAM stands for dynamic random access memory, a type of memory used in most personal computers.
Types of DRAM Packages and DRAM Memory
LAPTOP MEMORY
(72, 144, 200) SO-DIMMSO-DIMM Short for Small Outline DIMM, a small version of a DIMM used commonly in notebook computers. 72 supports 32bit and 144 and 200 SO-DIMM pins supports a full 64-bit transfer.
(144, 172) Micro-DIMMMicro-DIMM Short for Micro Dual Inline Memory Module, a competing memory used on laptops, mostly supports 144 and 172 pins.
SIMM Acronym for single in-line memory module, a small circuit board that can hold a group of memory chips. Typically, SIMM's holds up 8 (on Macintoshes) or 9 (on PCs) RAM chips. On PCs, the ninth chip is often used for parity error checking. Unlike memory chips, SIMM's is measured in bytes rather than bits. SIMM's is easier to install than individual memory chips. A SIMM is either 30 or 72 pins.
30 pin SIMM (Usually FPM or EDO RAM)
FPM RAM Short for Fast Page Mode RAM, a type of Dynamic RAM (DRAM) that allows faster access to data in the same row or page. Page-mode memory works by eliminating the need for a row address if data is located in the row previously accessed. It is sometimes called page mode memory.
72 pin SIMM (EDO RAM)EDO DRAM Short for Extended Data Output Dynamic Random Access Memory, a type of DRAM that is faster than conventional DRAM. Unlike conventional DRAM which can only access one block of data at a time, EDO RAM can start fetching the next block of memory at the same time that it sends the previous block to the CPU.
DIMM Short for dual in-line memory module, a small circuit board that holds memory chips. A single in-line memory module (SIMM) has a 32-bit path to the memory chips whereas a DIMM has 64-bit path. Because the Pentium processor requires a 64-bit path to memory, you need to install SIMM's two at a time. With DIMM's, you can install memory one DIMM at a time. A DIMM contains 168 pins.
168 pin DIMM (SDRAM)
SDRAM Short for Synchronous DRAM, a new type of DRAM that can run at much higher clock speeds than conventional memory. SDRAM actually synchronizes itself with the CPU's bus and is capable of running at 133 MHz, about three times faster than conventional FPM RAM, and about twice as fast EDO DRAM . SDRAM is replacing EDO DRAM in many newer computers
SDRAM delivers data in high speed burst
SDRAM delivers data in high speed burst
184 pin DIMM (DDR-SDRAM)DDR SDRAM Short for Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle, effectively doubling the memory chip's data throughput. DDR-SDRAM is also called SDRAM II.
240 DIMM (DDR2-SDRAM)
DDR2-SDRAM Short for Double Data Rate Synchronous DRAM 2 is a type of DDR that supports
higher's speeds than it's predecessor DDR SDRAM
higher's speeds than it's predecessor DDR SDRAM
240 DIMM (DDR3-SDRAM)
DDR3-SDRAM Short for Double Data Rate Synchronous DRAM 3 is the newest type of DDR that supports
the fastest speed of all the SDRAM memory
the fastest speed of all the SDRAM memory
184 pin RIMM (RDRAM)RIMM Rambus Inline Memory Module, The memory module used with RDRAM chips. It is similar to a DIMM package but uses different pin settings. Rambus trademarked the term RIMM as an entire word. It is the term used for a module using Rambus technology. It is sometimes incorrectly used as an acronym for Rambus Inline Memory Module. A RIMM contains 184 or 232pins. Note must use all sockets in RIMM installation or use C_RIMM to terminate banks
232 pin RIMM (RDRAM)
RDRAM Short for Rambus DRAM, a type of memory (DRAM) developed by Rambus, Inc.
In 1997, Intel announced that it would license the Rambus technology for use on its future motherboards, thus making it the likely de facto standard for memory architectures.
In 1997, Intel announced that it would license the Rambus technology for use on its future motherboards, thus making it the likely de facto standard for memory architectures.
CLICK HERE for a picture and more information on RIMM Installation
SIMM and DIMM Sockets
SDRAM Chart
168 DIMM (SDRAM)| Module Standard | Module Format | Chip Type | Clock Speed (MHz) | Cycles Per clock | Bus Speed | Bus Width (Bytes) | Transfer Rate (MB/s) |
| PC66 | SDR DIMM | 10ns | 66 | 1 | 66 | 8 | 533 |
| PC100 | SDR DIMM | 8ns | 100 | 1 | 100 | 8 | 800 |
| PC133 | SDR DIMM | 7ns | 133 | 1 | 133 | 8 | 1,066 |
DDR SDRAM Chart
184 DIMM (DDR-SDRAM)| Module Standard | Module Format | Chip Type | Clock Speed (MHz) | Cycles Per clock | Bus Speed | Bus Width (Bytes) | Transfer Rate (MB/s) |
| PC1600 | DDR DIMM | DDR200 | 100 | 2 | 200 | 8 | 1,600 |
| PC2100 | DDR DIMM | DDR266 | 133 | 2 | 266 | 8 | 2.133 |
| PC2700 | DDR DIMM | DDR333 | 166 | 2 | 333 | 8 | 2,667 |
| PC3200 | DDR DIMM | DDR400 | 200 | 2 | 400 | 8 | 3,200 |
| PC4000 | DDR DIMM | DDR500 | 250 | 2 | 500 | 8 | 4,000 |
| PC4300 | DDR DIMM | DDR533 | 266 | 2 | 533 | 8 | 4,266 |
DDR2 SDRAM Chart
240 DIMM (DDR2-SDRAM)| Module Standard | Module Format | Chip Type | Clock Speed (MHz) | Cycles Per clock | Bus Speed | Bus Width (Bytes) | Transfer Rate (MB/s) |
| PC2-3200 | DDR2 DIMM | DDR2-400 | 200 | 2 | 400 | 8 | 3,200 |
| PC2-4300 | DDR2 DIMM | DDR2-533 | 266 | 2 | 533 | 8 | 4,266 |
| PC2-5400 | DDR2 DIMM | DDR2-667 | 333 | 2 | 667 | 8 | 5,333 |
| PC2-6400 | DDR2 DIMM | DDR2-800 | 400 | 2 | 800 | 8 | 6,400 |
240 DIMM (DDR3-SDRAM)| Module Standard | Module Format | Chip Type | Clock Speed (MHz) | Cycles Per clock | Bus Speed | Bus Width (Bytes) | Transfer Rate (MB/s) |
| PC3-6400 | DDR3 DIMM | DDR3-800 | 400 | 2 | 800 | 8 | 6,400 |
| PC3-8500 | DDR3 DIMM | DDR3-1066 | 533 | 2 | 1,066 | 8 | 8,500 |
| PC3-10600 | DDR3 DIMM | DDR3-1333 | 667 | 2 | 1,334 | 8 | 10,670 |
| PC3-12800 | DDR3 DIMM | DDR3-1600 | 800 | 2 | 1,600 | 8 | 12,800 |
RDRAM Chart
232 RIMM (RDRAM)| Module Standard | Module Format | Chip Type | Clock Speed (MHz) | Cycles Per clock | Bus Speed | Bus Width (Bytes) | Transfer Rate (MB/s) |
| RIMM 1200 | RIMM-16 | PC600 | 300 | 2 | 600 | 2 | 1,200 |
| RIMM 1400 | RIMM-16 | PC700 | 350 | 2 | 700 | 2 | 1,400 |
| RIMM 1600 | RIMM-16 | PC800 | 400 | 2 | 800 | 2 | 1,600 |
| RIMM 2100 | RIMM-16 | PC1066 | 533 | 2 | 1,066 | 2 | 2,133 |
| RIMM 2400 | RIMM-16 | PC1200 | 600 | 2 | 1,200 | 2 | 2,400 |
| RIMM 3200 | RIMM-32 | PC800 | 400 | 2 | 800 | 2 | 3,200 |
| RIMM 4200 | RIMM-32 | PC1066 | 533 | 2 | 1,066 | 2 | 4,266 |
| RIMM 4800 | RIMM-32 | PC1200 | 600 | 2 | 1,200 | 2 | 4,800 |
RAM Desktop Installation
Note RAM Memory Sticks come in the following sizes
Note RAM Memory Sticks come in the following sizes
8MB, 16MB, 32MB, 64MB, 128MB, 256MB, 512MB, 1GB, 2GB, 4GB and 8GB
SIMM – Single Inline Memory Module Installation (30 or 72 pin)
1. Place SIMM in a 45 degree angle, push it upright to lock with the corresponding notch on the sides
2. Must be installed in same pairs
3. Must populate first two slots of the SIMM sockets in order for it to work
2. Must be installed in same pairs
3. Must populate first two slots of the SIMM sockets in order for it to work
DIMM – Dual Inline Memory Module Installation (168, 184 or 240 pin)
1. The first thing you do is open the plastic retaining clips on each side of slots you are going to use.
2. Align the cut-out on the module pin connector with the engaging pin on the slot
3. Holding the module upright press down both ends.
4. When the module is correctly seated, retaining clips should lock automatically.
5. DIMM’s can be installed as a single pair (unless it states Dual Channel then you must install it in pairs)
2. Align the cut-out on the module pin connector with the engaging pin on the slot
3. Holding the module upright press down both ends.
4. When the module is correctly seated, retaining clips should lock automatically.
5. DIMM’s can be installed as a single pair (unless it states Dual Channel then you must install it in pairs)
RIMM – Rambus Inline Memory Module Installation (184 or 232 pin)
1. The first thing you do is open the plastic retaining clips on each side of slots you are going to use.
2. Align the cut-out on the module pin connector with the engaging pin on the slot
3. Holding the module upright press down both ends.
4. When the module is correctly seated, retaining clips should lock automatically.
5. Must populate all RIMM slots available
3. If not unpopulated slots must use CRIMM’s (Continuity Rambus Inline Memory Module)
Memory Troubleshooting
MEMORY (when installing use a ground strap because of ESD)
ESD (low and high humidity)
Mixed Memory usually equals fried memory
Parity Errors or ECC Errors (Memory correction errors)
SIMMS must be installed in pairs
RIMMS must be all installed in all slots or CRIMM's must be needed in unvacated RIMM slots
General Protection Fault (memory overwrite)
Not enough memory (computer is slow)
NMI -Non Maskable Interrupt will cause BSOD (Blue Screen of Death)
Multiple beeps when booting up check that memory is properly installed and working
No Video (Reseat memory)
Memory speeds set in BIOS/CMOS Setup
Virtual Memory (Page fault)
Chip Creep - Thermal expansion and contraction
ESD (low and high humidity)
Mixed Memory usually equals fried memory
Parity Errors or ECC Errors (Memory correction errors)
SIMMS must be installed in pairs
RIMMS must be all installed in all slots or CRIMM's must be needed in unvacated RIMM slots
General Protection Fault (memory overwrite)
Not enough memory (computer is slow)
NMI -Non Maskable Interrupt will cause BSOD (Blue Screen of Death)
Multiple beeps when booting up check that memory is properly installed and working
No Video (Reseat memory)
Memory speeds set in BIOS/CMOS Setup
Virtual Memory (Page fault)
Chip Creep - Thermal expansion and contraction
Special Thanks to Rambus, Cosair, PNY, Viking, American Megatrends, Centon, Samsung, Crucial and Micron
RAM vs ROM
RAM (Random Access Memory) and ROM (Read Only Memory) are two very old technologies that were created in the very early days of computing. Despite that, they are still used nowadays even if the technical definitions of the two are not as applicable as before. The main difference between RAM and ROM is their use. ROM is used to store the code for programs that are run in the processor. In comparison, RAM is used to hold the temporary data that is created and used by the program.
RAM was so named because any area of the memory can be quickly accessed without having to go through everything else. This was in contrast to tap drives, where access time is linearly related to the current position of the head to the position of the data. The way ROM was named is also very similar; because old ROMs are made with the data built-in and there is no way to change it. Of course, both of these are no longer applicable. DRAM chips are actually accessed in bursts rather than randomly. ROMs are now made with flash memory that can be easily written to. Still, the old terminologies have been stuck ever since.
RAM is a volatile memory type, which means that it loses its content once power is removed. This is the reason why it cannot replace ROM, which retains its content even when not powered. The downside of ROM is its much slower speed. Using it to replace RAM would make a computer perform very slow.
Nowadays, RAM is seen mainly as the primary memory of computers and other gadgets like smartphones and tablets. In portable gadgets, the internal memory reserved for applications is often referred to as ROM. But in computers, ROMs retains its original meaning. The chip used to hold the BIOS is a ROM as it isn’t routinely written to; but it is sometimes updated. Optical drives are also called ROMS (i.e. CD-ROM and DVD-ROM) as they do read discs that cannot be written to; but most optical drives also have the ability to write to blank discs.
Summary:
ROM is used for storing programs while RAM is used by programs to hold temporary data
RAM is a type of memory that can be accessed non-sequentially while ROM is a type of memory that is only read in typical operation
ROM is non-volatile while RAM is volatile
RAM is considerably faster than ROM
ROM is used for storing programs while RAM is used by programs to hold temporary data
RAM is a type of memory that can be accessed non-sequentially while ROM is a type of memory that is only read in typical operation
ROM is non-volatile while RAM is volatile
RAM is considerably faster than ROM
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