Fully-Buffered Double Data Rate Synchronous DRAM Dual In-Line Memory
Module:
Fully-Buffered DIMM [FB-DIMM, or FBDIMM] utilizes the JEDEC standard for
Double Date Rate2 [DDR II] SDRAM. This page covers the FB-DIMM modules,
refer to the general Memory Module page for
a more complete listing of different types of modules, manufactures and
descriptions. FB-DIMM modules are Fully-Buffered [on-board] at the
high-speed Advanced Memory Buffer (AMB). Unlike normal DIMM modules which
are connected in parallel to the memory controller [off a stub], FBDIMM
modules are connected in a point-to-point serial architecture. The
'first' on-board buffer [AMB] provides a bi-directional interconnect to
the memory controller [northbound] on the motherboard, and a different
bi-directional interconnect to the next DIMM in the bank [southbound].
The second FB-DIMM connects to the first DIMM [northbound] and the next
one in the chain [southbound] . A maximum of eight DIMMs may be connected
using the FBDIMM approach. Each FBDIMM in the bank receives its own clock
line from a common clock source. The FB-DIMM modules may also reside on a
memory riser card, but a repeater may be
required. The southbound lanes consist of 10 differential lines [2 x 10],
while the northbound lanes consist of 14 differential lines [2 x
14]
FB-DIMM memory modules use the SMBus for 100kHz communication with the AMB configuration registers [as a slave]. The SMbus interface is independent of the FBDIMM link. Address and data is transmitted as a differential [800mv] point-to-point signal on a 50 W terminated line. The clock runs through the FB-DIMM and is terminated on the motherboard. The HCSL [High Speed Current Steering Logic] clock runs at 1/4 the DDR2 DRAM frequency [133, 166, and 200MHz]. The power supply is 1.5 volts.
I found this text on the web about power dissipation but have yet to
verify it.
A DDR DIMM requires 5.4 watts, a DDR2 DIMM needs 4.4 watts and a DDR2
FB-DIMM requires near 10.4 watt.
FB-DIMM are currently produced in speeds of PC2-4200, PC2-5300, and
PC2-6400. Transmission rates for the 'PC2-xx' series of devices:
PC2-4200 (DDR2-533 SDRAM); Clock Speed: 266MHz, Data Rate: 533MHz,
Through-put 4200MB/s
PC2-5300 (DDR2-667 SDRAM); Clock Speed: 333MHz, Data Rate: 663MHz,
Through-put 5300MB/s
PC2-6400 (DDR2-800 SDRAM); Clock Speed: 400MHz, Data Rate: 800MHz,
Through-put 6400MB/s
The physical size of the FBDIMM stick is 133.5mm x 30.5mm, at 240 fingers. The notch {key} is 8mm right of center [or 74.68mm from left side], which differs from Registered DIMM modules at 4mm right of center. The FB-DIMM pin out is listed on the FBDIMM Pinout page.
Transfer Rate | UI Nom | TTx-Total-min | TTX-Eye-Median-Max-Jitter |
(Gbps) | (ps) | (ps) | (ps) |
3.2 | 312.0 | 248.5 | 32.0 |
4.0 | 250.0 | 191.0 | 29.5 |
4.8 | 208.0 | 157.0 | 25.68 |
Transfer Rate | UI Nom | TRX-Total Min | TRX-EYE-Median-Max-Jitter | VRX-DIFF p-p-MIN |
(Gbps) | (ps) | (ps) | (ps) | (mV) |
3.2 | 312.0 | 115 | 98.67 | 170 |
4.0 | 250.0 | 90 | 80 | 170 |
4.8 | 208.0 | 75 | 66.68 | 170 |
FB-DIMM Speed offerings include 533Mbps [DDR2-533], 667Mbps [DDR2-667],
and 800Mbps [DDR2-800].
The electrical interfaces used by memory modules which include LVTTL,
SSTL, and HSTL and others are listed on the IC Bus page. Memory chips/
Memory IC manufacturers are listed on the Memory IC page.
The Advanced Memory Buffer [AMB] chip is the memory module's interface between the mother board memory controller IC and all other FB-DIMM modules on the motherboard.
IDT {Advanced Memory Buffer (AMB) device Supports DDR2-533, DDR2-667, DDR2-800 memory}
Renesas {Advanced Memory Buffer (AMB) SDRAM interface connects to DDR2-533, DDR2-667 and DDR2-800 devices}
Server applications implement FB-DIMM modules because of their
requirement for large amounts of memory.
FB-DIMM modules are not found in
desktops because of the high cost of the modules.
However FB-DIMM memory
may be found in some high-end workstations.
Both Road-Maps from AMD and Intel show that FB-DIMMs are being dropped from all but a few server lines as of 2007.
Centon Electronics {PC2-4200F; 512MB Fully Buffered DIMM DDR2 ECC SDRAM Memory module is 67,108,864words by 72bit 240-pin Dual In-line Memory Module(DIMM), assembled with 9 pieces of a 64MX8bit DDR2 SDRAM in FBGA package}
Hynix Semiconductor America Inc. {512MB, 1GB and 2GB density FB-DIMM}
Micron Technology, Inc {Single-rank / Dual-rank, x8-based, PC2-4200/PC2-5300}
Super Talent Technology {DDR2 FB DIMMs to 4GB; PC2-4300, PC2-5300, PC2-6400}
DIMM Sockets; DIMM/SIMM Socket Manufacturers.
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