Memory Modules OverviewSpring, 2004
Bill GervasiSenior Technologist, Netlist
Chairman, JEDEC Small Modules& DRAM Packaging Committees
Many Applications,
Many Configurations
Module Configurations
• DDR1– Unbuffered DIMM– Registered DIMM– SO-DIMM– Micro-DIMM
• New:– 32b-DIMM
• In development:– 4 Rank RDIMM
• DDR2– Unbuffered DIMM– Registered DIMM– SO-DIMM– Micro-DIMM
• In development:– Mini-RDIMM– 4 Rank RDIMM– 4 Rank SO-DIMM– 4 Rank Micro-DIMM– Fully Buffered DIMM– DDR3 modules
All JEDEC modules include Serial Presence Detect (SPD) EEPROM for boot time detection of capabilities
DDR2 Speed GradingCommittee approved standard speed grades:
400 MT/s 200 MHz DDR2-400 PC2-3200
533 MT/s 266 MHz DDR2-533 PC2-4200
667 MT/s 333 MHz DDR2-667 PC2-5300
800 MT/s 400 MHz DDR2-800 PC2-6400
Data Rate
X64/x72 bit data bus * chip speed
Clock Speed Chip Bin Module Bin
DDR2 Unbuffered DIMM
• Same physical size as DDR1: 133 mm (5.25”)• New socket
– More pins… 184 240 pins– Tighter pin pitch… 1.27 1.0 mm
• “Same plane referencing” pinout• Target markets unchanged
– Workstations– Desktop PC
• Status: APPROVED– 1 Rank x8, 2 Ranks x8, 1 Rank x16
DDR2 Registered DIMM
• Target markets unchanged– Servers– High-end Workstations
• New feature: Address Parity– Checks integrity of every
address and commandsent
• Status: APPROVED– 1 Rank x8, 2 Rank x8, 1 Rank x4, 2 Rank x4– With or without address parity
DDR2 SO-DIMM
• Same width, shorter than DDR1: 67.6 x 30 mm• Same 200 pin socket as DDR1
– Uses 1.8V key position• No longer supports x72 (ECC) or registered• Target markets change from DDR1 to DDR2:
– DDR1: Mobile, blade server– DDR2: Does not support blade server
• Status: APPROVED– 2 Rank x16, 1 Rank x8, 1 Rank x16, 2 Rank x8
DDR2 Micro-DIMM
• Larger module, same footprint as DDR1: 52 x 30 mm• New connector
– High pin count mezzanine connector– Two part: half on motherboard, half on module– 0.4 mm pitch
• Status: APPROVED– 1 Rank x16, 2 Rank x16
DDR1 32b-DIMM
• New to DDR1… noDDR2 version yet
• X32 only, 90.18 mm wide• Ultra low cost• New connector
– 100 pins, 1.27 mm pin pitch
• Target market: peripherals, e.g. printers• Status: APPROVED
– 1 Rank x16, 2 Rank x8, 1 Rank x8, 2 Rank x16
What is On the Horizon?
• DDR2 Mini-RDIMM
• 4 Rank DDR1 RDIMM
• 4 Rank DDR2 RDIMM, SO-DIMM, & Micro-DIMM
• Fully Buffered DIMM
• DDR3 modules
DDR2 Mini-RDIMM• New to DDR2… no DDR1
equivalent• Supports x72 (ECC) and
registered• Larger than SO-DIMM: 82 mm• New socket required
– 244 pins, 0.6 mm pin pitch
• Target market: blade server
4 Rank DDR1 RDIMM
• Doubles per-slot memory capacity to 4GB!• Takes advantage of existing chip selects• Requires additional signals routed on motherboard
• PC-3200 with a single slot
CS3#
CS0#CS1#CS2#
MemoryController
MemoryController
CS3#
CS0#CS1#CS2#
4 Rank DDR2 RDIMM
• Similar to DDR1 4 Rank• Supports address parity• Requires additional signals routed on motherboard
• PC2-4200 with a single slot… headroom to PC2-5300? PC2-6400?
CS3#
CS0#CS1#CS2#
MemoryController
MemoryController
CS3#
CS0#CS1#CS2#
Ad. Parity Ad. Parity
4 Rank DDR2 SO-DIMM, Micro-DIMM
• Highest capacity modules with 4 ranks of x8– 1GB using 256Mb (32 DRAMs)– 2GB using 512Mb– 4GB using 1Gb
• Lowest power modules with 4 ranks of x16– 512MB using 256Mb (16 DRAMs)– 1GB using 512Mb– 2GB using 1Gb– Estimated 20-25% reduction in power over x8
• Higher performance– Twice as many open pages possible
• Cost protection during density crossovers(like 512Mb1Gb)
Fully Buffered DIMM
Processor
DIMM
Problem - Stub Bus
DIMM
DIMM
DIMM
Each single sided DDR2-800 DIMM capable of 6.4 GB/s Four DIMMs capable of over 25 GB/s Bus Topology can not deliver the bandwidth to the application Stub bus only able to deliver the bandwidth of one DIMM Need headroom to support DDR3
FB-DIMM High Speed Channel
DDR3 Modules• Active development has begun• Performance to 1.6Gbps per pin• Point to point, point to 2 points• Fly-by buses with controller de-skew
Address, Command,
Clocks
Data,
Strobes
Controller
DR
AM
DR
AM
Keeping Them Straight
New label: 1GB 2Rx8 PC2-5300U-444 11-A1
1GB = Total module capacity
2Rx8 = Number of ranks of memory & chip width
PC2-5300 = Speed grade in MB/s across DIMM
U = Module type (unbuffered, registered, etc.)
444 = CAS latency–tRCD–tRP performance grade
11 = SPD revision (encoding + additions)
A1 = Standard board layout and revision
2004 Modules Summary
• DDR1 development continues– PC-3200 speed bumps, 32b DIMM, 4 Rank RDIMM
• DDR2 modules ready to roll out– UDIMM, RDIMM, SO-DIMM, Micro-DIMM
• DDR2 Speed Grades finalized– PC2-3200, PC2-4200, PC2-5300, PC2-6400
• New DDR2 modules in development– Mini-RDIMM, 4 rank R-/SO-/Micro-DIMM, FB-DIMM
• DDR3 modules development begun• New DIMM labels assist user identification
Thank You___
Q & A