ROM vs. RAM

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 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)

ECC-Error correction code use in memory correction for newer computers
Buffer vs. Unbuffer
Registered vs. Un Registered

Memory Banks - A socket where memory is installed Example 4 banks will have 8MB of memory each for a total of 32MB

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

SO-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-DIMM

Micro-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.

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.

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.

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

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.

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

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

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

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.

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

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

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

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

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

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

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)

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 (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

Special Thanks to Rambus, Cosair, PNY, Viking, American Megatrends, Centon, Samsung, Crucial and Micron