DRAM Future Perspectives, Are We Out of Gas? - Discobolus ...
DRAM Future Perspectives, Are We Out of Gas? - Discobolus ...
DRAM Future Perspectives, Are We Out of Gas? - Discobolus ...
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D ISCOBOLUS<br />
ESIGNS<br />
<strong>DRAM</strong> <strong>Future</strong> <strong>Perspectives</strong><br />
<strong>Are</strong> <strong>We</strong> <strong>Out</strong> <strong>of</strong> <strong>Gas</strong>?<br />
Bill Gervasi<br />
September 18, 2012
Current Lay <strong>of</strong> the Land<br />
CPU CPU CPU<br />
Unbuffered Registered Load Reduced<br />
CPU<br />
Each solution has trade<strong>of</strong>fs<br />
regarding frequency, latency,<br />
and capacity<br />
Solder Down<br />
2
Memory Chips & Stacks<br />
Classic window BGA<br />
Dual Face Down DDP<br />
RDL DDP<br />
3DS with<br />
through silicon vias<br />
3
Roadblocks<br />
Socket is the limiting factor, capacity req low<br />
Move to solder down<br />
UDIMM loading prevents address bus from getting<br />
better<br />
Move applications to RDIMM<br />
RDIMM loading prevents data bus from getting<br />
better<br />
Move applications to LRDIMM<br />
LRDIMM loading prevents capacity from getting<br />
better<br />
Move to memory hubs<br />
4
Memory Hub<br />
Hub<br />
CPU<br />
5
Combined Hub & 3DS<br />
Hub<br />
Inherits problems from the FB-DIMM generation<br />
SERDES run hot<br />
SERDES increase latency<br />
Minimum silicon size for hub is pretty large<br />
Must incorporate the entire controller<br />
ECC, sparing, refresh, etc.<br />
Political battle to hand over control to suppliers?<br />
6
Summary<br />
Current DDR4 roadmap carries us from 2014<br />
through 2020<br />
Application upscaling extends life 2-4 years<br />
Hubs or solder down delay need for stacking<br />
10 years or more to figure out how to yield 3DS<br />
7
Thank You<br />
Bill Gervasi<br />
<strong>Discobolus</strong> Designs<br />
bilge@discobolusdesigns.com
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