fully buffered dimm
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Very Low ProfileFully Buffered DIMM
Bill GervasiVice President, DRAM Technology
SimpleTech
The subject matter of this presentation is a work in progress. It had not been balloted or approved as a final JEDEC standard. Users should not rely on this presentation as indicative of the content of the final standard. JEDEC does not
endorse the content of this presentation. The views expressed are solely those of the author(s).
The subject matter is a work in progress, not a final JEDEC standard.
Fully Buffered DIMM
• Designed for needs of mid-range servers– Typically 8 or 16 FB-DIMM slots– 4GB per slot by the time it is ramping
(1Gb DRAMs) 32GB & 64GB servers– Only “standard” height is 30mm (1.2”)
• Need to penetrate broader markets to ensure success and reduce cost
The subject matter is a work in progress, not a final JEDEC standard.
Form Factor Wars
• 1.2” (30mm) standard chosen in 1999 based on 1U server market projections
• 1.2” (30mm) standard chosen in 1999 based on 1U server market projections
• But, market fragmenting– Blade needs 18.3mm (VLP)– 1U needs 30mm (LP)– 2U can use 38mm or taller
• OEMs “demand” one size fits all … but …
The subject matter is a work in progress, not a final JEDEC standard.
High Profile Module2U Server
Side
View
• Lots of headroom due to huge heat sinks
• Tall module (e.g., 38mm) fits fine
• Better thermal characteristics
• More DRAM supplier options
30mm38mm
CPUHeatSink
The subject matter is a work in progress, not a final JEDEC standard.
Standard Profile Module
Angled Socket
17700 mm2
Co
ol
Air
Hea
ted
Air
Top
View
CPU
CPU
30 mm DIMM
Blade Server
The subject matter is a work in progress, not a final JEDEC standard.
Very Low Profile Module
Angled Socket
Vertical Socket
2 x 2200 mm2
75% Reduction!
Co
ol
Air
Hea
ted
Air
Blade Server
30 mm DIMM
18.3 mm DIMM
CPU
CPU
Top
View
The subject matter is a work in progress, not a final JEDEC standard.
The VLP Form Factor133.35 mm
(5.25”)
4 mm(0.158”)
14.3 mm(0.56”)Usable
Layout Area
18.3 mm(0.72”)
The subject matter is a work in progress, not a final JEDEC standard.
FB-DIMM Differentiation• How to build a better FB-DIMM
– Improved thermal solutions– How about a VLP FB-DIMM?
• Challenge #1: AMB is 19.2mm tall!
• Good thing guyslike us like to pack10 pounds into a 5pound sack…
19.2 mm(0.76”)
24 mm(0.95”)
The subject matter is a work in progress, not a final JEDEC standard.
FB-DIMM Differentiation• Notice that the AMB has huge windows in the array• This choice was based on some assumptions:
– FB-DIMM must be possible in6 layers
– No blind vias required
• However, what if you’re willing to go to 8 layers and use blind vias?
The subject matter is a work in progress, not a final JEDEC standard.
Honey, I Shrunk the AMB
655 ball AMB29x23 ball array (ball pitch 0.8mm)
24.5 x 19.5mm package
510 ball VLP-AMB31x17 ball array (ball pitch 0.8mm)
26 x 14mm package
The subject matter is a work in progress, not a final JEDEC standard.
Can the AMB Be THAT Small?
The AMB die size is not the limiter… it’s the number of balls on the package that
defines its footprint.
The subject matter is a work in progress, not a final JEDEC standard.
VLP FB-DIMMStacked 2GB
The subject matter is a work in progress, not a final JEDEC standard.
DRAM Size
• Max DRAM package supported in VLP= 12.3 x 14.3 mm
• This supports most 512Mb chips now
• 1Gb shrinks with 70 nm process– 4GB VLP FB-DIMM enabled
The subject matter is a work in progress, not a final JEDEC standard.
A Simpler Variation
• Primary-only interface – no southbound
• Uses 4-channel memory controller
• Eliminates 100 balls, 1W per AMB
“Lo
w E
nd
” F
B-D
IMM
C
on
tro
ller
“Hig
h E
nd
” F
B-D
IMM
C
on
tro
ller
The subject matter is a work in progress, not a final JEDEC standard.
Current Status
• Getting customer input on primary-only AMB• Mechanical feasibility done• Re-ballout analysis under way with AMB
suppliers• Thermal analysis under way
– Improved airflow with lower ambient– Less radiating space– Heat sinking solutions to be developed
• Socket analysis begun
The subject matter is a work in progress, not a final JEDEC standard.
Thank You
• Questions?
Bill [email protected]