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DRAM Packages
Physical DRAM Packages
• Physically, the main memory in a system is a collection of
–Chips or
–Modules containing chips • that are usually plugged into the motherboard.
• These chips or modules vary in their electrical and physical designs and must be compatible with the system into which they are being installed to function properly.
CPU and Chipset
• The CPU and motherboard architecture (chipset) dictates a particular computer’s physical memory
–Capacity,
–Speed and –Data bus width requirements
• that can be installed.
Individual Memory Chips
• Originally, systems had memory installed via individual chips.
• They are often referred to as dual inline package (DIP) chips because of their designs.
• The original IBM XT and AT had 36 sockets on the motherboard
• for these individual chips, and then more of them were installed on the memory cards plugged into the bus slots.
DIP Packages
Apple-I single board computer
Problems of using DIP Memory Chips
• Time-consuming, and Labor-intensive way to deal with memory,
• They crept out of their sockets over time.
Solution
• The alternative to this at the time was to have the memory soldered into either the motherboard or an expansion card.
• Made memory troubleshooting difficult.
Module
• What was necessary was a chip that was both soldered and removable, and that is exactly what was found in the module called a SIMM.
Different types of Module
• For memory storage, most modern systems have adopted the
–SIMM (single inline memory module),
–DIMM (dual inline memory module), or
–RIMM (Rambus Inline Memory Module) • as an alternative to individual memory chips.
Modules
• These small boards plug into special connectors on a motherboard or memory card.
• The individual memory chips are soldered to the module, so removing and replacing them is impossible.
• Instead, you must replace the entire module if any part of it fails.
• The module is treated as though it were one large memory chip.
SIMM (Single In-line Memory Module)
• 30-pin SIMM has 8-bit data bus
• 72-pin SIMM has 32-bit data bus
• May have several chips (ex: 2, 3, 8, 9)
Bank of Memory
• A bank of memory must contain the same amount of bits as the data bus of the CPU/System.
Number of Modules make a Memory Bank
Processor Data bus Bank SizeNo Parity
Bank SizeParity
30-PinSIMMs
72-PinSIMMs
168-PinDIMMs
8088 8-bit 8 bits 9 bits 1 n/a n/a8086 16-bit 16 bits 18 bits 2 n/a n/a286 16-bit 16 bits 18 bits 2 n/a n/a386SX, SL, SLC 16-bit 16 bits 18 bits 2 n/a n/a486SLC, SLC2 16-bit 16 bits 18 bits 2 n/a n/a386DX 32-bit 32 bits 36 bits 4 1 n/a486SX, DX, DX2,DX4,5x86
32-bit 32-bits 36 bits 4 1 n/a
Pentium, K6 series 64-bit 64 bits 72 bits 8 2 1Pentium pro, PII,Celeron, PIII,P4,Athlon/Duron
64-bit 64 bits 72 bits 8 2 1
A typical 30-pin SIMM Dimensions
The one shown here is 9-bit, although the dimensions would be the same for 8-bit.
30-pin and 72-pin SIMM Pictureshttp://www.simmtester.com/page/news/showpubnews.asp?num=44
A typical 72-pin SIMM
A typical 168-pin SDRAM DIMM
A typical 184-pin DDR DIMM
A typical 184-pin RIMM
SDRAM-DIMM vs. DDR-DIMM vs. RIMM
SDRAM-DIMM vs. DDR-DIMM vs. RIMM
Characteristics of 168-pin SDRAM DIMM
• The DIMM uses serial presence detect (SPD).
• It consists of a small EEPROM or Flash memory chip on the DIMM that contains specially formatted data indicating the DIMM’s features.
• This serial data enables the motherboard to autoconfigure to the exact type of DIMM installed.
Characteristics of 168-pin SDRAM DIMM
• DIMMs can come in several varieties, including
– unbuffered or buffered and
– 3.3V or 5V.
• All PC systems use unbuffered DIMMs.
• DIMM designs for PCs are almost universally 3.3V.
• If you install a 5V DIMM in a 3.3V socket, it would be damaged, but fortunately, keying in the socket and on the DIMM prevents that.
168-pin DRAM DIMM notch key definitions
RDRAM bus layout showing a RIMM and one continuity module
The markings on a typical memory chip
Installing SIMM• Align the module (notch and protrusions in the socket).
The notch on this SIMM is shown on the left side. • Insert the SIMM at a 45° angle
• and then tilt it forward until the locking clips snap into place.
Removing SIMM• Pull plastic tabs outward• Push the top at an angle away from the socket• Pull out of the socket
Installing DIMM / RIMM• Align the module (notch and protrusions in the socket)• Insert at a straight angle (90º)
• Push until the ejector tab locks into place in the notch on the side of the DIMM.
Removing DIMM / RIMM• Push out the ejector tabs and the DIMM will pop out.
72-pin SODIMM (Small Outline DIMMs)
72-pin SODIMMs are typically used in the Pentium-II Laptop computer system
144-pin SODIMM (Small Outline DIMMs)
• 144- SODIMMs are typically used in the PC66 and PC100 SDRAM Laptop compatible computers
100-pin SODIMM (Small Outline DIMMs)
• 100- PIN DIMMs are primarily used in printers
144- PIN Micro-DIMMs
• 144- PIN Micro-DIMMs are primarily used in digital assistants, subnotebooks and notebook computers.
200- Pin DDR-SODIMM