DDR3 Thermals - Micron

4/12/2007 

DDR3 Thermals 

Thermal Limits, Operating Temperatures, 

Tools, and System Development 

©2007 Micron Technology, Inc. All rights reserved. Products are warranted only to meet Micron’s production data sheet specifications. 

Information, products and/or specifications are subject to change without notice. All information is provided on an “AS IS” basis without 

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• DDR3 Thermal Limits 

4/12/2007 2 

©2007 Micron Technology, Inc. All rights reserved. 

Agenda 

• Estimated DDR3 DRAM Operating Temperatures 

• Possible Thermal Solutions 

• Micron Thermal Tools and System Development

4/12/2007 

DDR3 Thermals 

Thermal Limits

4/12/2007 4 


DDR3 Thermal Limits 

• DDR3 is specified to operate at the standard 85°C case or 

an extended temperature range of 95°C with 2X the 

refresh rate 

� 1X (standard) refresh rate = 64ms 

� 2X (high temp) refresh rate = 32ms

• Running at the higher temperature also requires the 

Extended Mode register to be set 

• This ensures the DRAM will perform a 2X (32ms) refresh 

while the part is in Self-Refresh mode 

4/12/2007 5 


DDR3 Thermal Limits


4/12/2007 6 


Agenda 




4/12/2007 7 


DRAM Temperatures 

• Simulation was performed to evaluate the thermal 

performance of several DDR3 RDIMMs 

� SR x4, DR x8, DR x4 (planar) and DR x4 (stacked) 

• The simulation was done for two worst case operating 

conditions 

� 100% DRAM bandwidth from a single Rank 

� ~65% DRAM utilization equally split between all Ranks 

• Each condition was repeated for the three key DDR3 

speed grades 

� DDR3-800, DDR3-1067, DDR3-1333

• General System Module 

4/12/2007 8 



• Duct width is set to 

maintain the same air 

speed between 1 DIMM/ch 

and 2 DIMMs/ch 

• With FMHS the duct area 

and inlet air speed are the 

same, so the air speed and 

pressure differential 

through the DIMMs 

increase due to reduced 

area cross-section

• Raw Cards Simulated 

4/12/2007 9 



R/C B (DR x8) R/C C (SR x4) 

R/C D (DR x4) - Stacked 

R/C J (DR x4) - Planar

Inlet Air (C) 

Requirements to Keep DRAM At/Below 85°C 

10 

0 

10 

20 

30 

40 

50 

60 

70 

0.00 0.50 1.00 1.50 2.00 2.50 3.00 

4/12/2007 10 


Air Speed at mid DIMM (m/s) 

65% Bandwidth (closed page) 

DR x8 (2GB) - Max DRAM temp = 85C with 0.4" pitch 

SingleSlot, DDR3-1067, 65% BW 

How to read the chart... 

For a single DR x8 (2GB) RDIMM running at DDR3- 

1066 speeds with a 65% DRAM utilization, closed 

page policy... the hottest DRAM case temperature 

is 85C when the inlet air is about 42C and there is 

a constant 1m/s of air flow 

�100% Bandwidth is from a single Rank, open page with continuous READs 

� 65% Bandwidth reflects a sustained channel bandwidth of 65% of the maximum DRAM BW, 2x READs to 

WRITEs distributed evenly through all available ranks, closed page, PLL/Register package included

Inlet Temp (C) 


10 


0.00 0.50 1.00 1.50 2.00 2.50 3.00 

0 

10 

20 

30 

40 

50 

60 

70 

4/12/2007 11 


100% Bandwidth (open page) 

Single Slot, DDR3-1067, 65% BW 

SingleSlot, DDR3-1067, 100% BW 

65% Bandwidth (closed page) 

DR x8 (2GB) - Max DRAM temp = 85C with 0.4" pitch 

What does this show? 

With high DRAM utilization, the (DR x8) runs 

cooler with open pages as compared to running 

with closed pages – about 6C cooler 




Inlet Temp (C) 

-10 

0 

10 

20 

30 

40 

50 

60 

70 


0.00 0.50 1.00 1.50 2.00 2.50 3.00 



WRITEs distributed evenly through all available ranks, closed page, PLL/Register package included 

4/12/2007 12 


Air speed at mid DIMM (m/s) 

DRx8 (2GB) - Max DRAM temp = 85C with 0.4" pitch 

Two Slots Populated, 1333MHz, 65% BW 



Single Slot, 1333MHz, 65% BW 




Single Slot, 800MHz, 100% BW

Inlet temp (C) 

-10 

0 

10 

20 

30 

40 

50 

60 

70 


0.00 0.50 1.00 1.50 2.00 2.50 3.00 




4/12/2007 13 



SRx4 (2GB) Max DRAM temp = 85C with 0.4" pitch 











-10 

0 

10 

20 

30 

40 

50 

60 

70 


0.00 0.50 1.00 1.50 2.00 2.50 3.00 




4/12/2007 14 


Air Sped at mid DIMM (m/s) 

DR x4 (4GB) Stacked - Max DRAM temp = 85C with 0.4" pitch 











-10 

0 

10 

20 

30 

40 

50 

60 

70 


0.00 0.50 1.00 1.50 2.00 2.50 3.00 




4/12/2007 15 



DRx4 (4GB) Planar - Max DRAM temp = 85c with 0.4" pitch 




Two Slots Populated, DDR3-1333, 65% BW 





Two Slots Populated, DDR3-800, 65% BW


• The simulations were then repeated with a full module 

heat spreader (FMHS) attached to each module 

• The FMHS used was: 

� A clamshell style heat spreader similar to FBDIMM 

� Anodized 1mm 1050 aluminum alloy 

� 15mil to 20mil gap pad TIM (1W/mK) 

� Used two (2) clips to fasten to the module 

4/12/2007 16 

©2007 Micron Technology, Inc. All rights reserved.

DDR3 RDIMM Thermals - Including Heat Sink 

Junction temp (C) 

140 

130 

120 

110 

100 

90 

80 

70 

60 

4/12/2007 17 


DRx4 (4G) Planar Max DRAM Temperatures with 40C inlet 

Pitch = 0.4 inch 

Without Heat Sink 

0.50 1.00 1.50 2.00 2.50 3.00 3.50 

Mid air speed (m/s) 


Single Slot - With Heat Sink, DDR3-1333, 65% BW 

Two Slots Poulated, DDR3-1333, 65% BW 

Two Slots Populated - With Heat Sink, DDR3-1333, 

65% BW 

With heat Sink 




DDR3 RDIMM Thermals - Including Heat Sink 

Junction temp (C) 

140 

130 

120 

110 

100 

90 

80 

70 

60 

4/12/2007 18 


DRx4 (4GB) - Stacked, Max DRAM Temperatures with 40(C) Inlet 

Without Heat Sink 

Pitch = 0.4 inch 

Delta is about 3C 

0.50 1.00 1.50 2.00 2.50 3.00 3.50 

Mid air speed (m/s) 


Single Slot - With Heat Sink, DDR3-1333, 65% BW 


Two Slots Populated - With Heat Sink, DDR3-1333, 65% BW 

Delta is about 6C 

With heat Sink 




4/12/2007 19 


Conclusion of Simulations 

• At the slower speeds, DDR3 RDIMMs run cooler than 

comparable DDR2 RDIMM modules 

• At the higher DDR3 clock rates and with minimal air flow, 

DRAM will approach or exceed the 85°C level 

• A module heat sink provides cooling benefits and may be 

required for high speed, high density modules


4/12/2007 20 


Agenda 




• System designs that utilize DDR3 must be proactive and 

consider the thermal aspects 

� Will modules need heat sinks? 

� Will there need to be an increased air flow? 

� Will the inlet air temperature need to be cooler? 

� Will socket spacing need to be increased? 

� Will the controller need to consider throttling? 

4/12/2007 21 


Possible Thermal Solutions

• Cooling the DDR3 RDIMM is different than cooling the 

FBDIMM 

� On the FBDIMM, it is the AMB that needs cooling and the 

heat sink actually dissipates heat from the AMB into the 

DRAM 

� The DDR3 RDIMM may need a heat sink to cool the DRAM 

4/12/2007 22 


Possible Thermal Solutions 

FBDIMM DDR3 RDIMM

• A full module heat spreader decreases the DRAM and register 

temperatures; but to get the full benefits of the heat sink, increased air 

flows are required 

4/12/2007 23 



Comparing the RDIMM (with) and 

(without) a heat sink shows even a 

greater difference between the DRAM 

temperature at higher airflow 

•3C delta at 1m/s 

•6C delta at +2.5m/s

• We may want to have the DDR3 modules updated to 

accept industry standard heat spreaders? 

� The PCBs may need to have notches added to accommodate 

the heat sink and mounting hardware (like on the FBDIMM) 

4/12/2007 24 



• When adding heat sinks, system designers will need to account 

for the increased pressure drop through the DIMMs with fan 

selection and DIMM layout 

4/12/2007 25 



•May need a higher pressure fan 

•May need a greater DIMM pitch

• An example of 0.4” DIMM pitch, without heat sinks 

4/12/2007 26 



About a 50% reduction

• An example of 0.4” DIMM pitch, with heat sinks 

4/12/2007 27 



About a 70-80% reduction

• The affects of increasing the socket pitch to 0.45” 

Max DRAM Temp (C) 

98 

96 

94 

92 

90 

88 

86 

84 

82 

80 

A decrease of about 5-6C is realized just by increasing the socket pitch to 0.45 inch 

4/12/2007 28 



2GB (SR x4) - Single Slot Populated, Inlet Air = 50C 

DDR3-1066 DDR3-1333 

0.40 inch pitch wo/HS 

0.40 inch pitch w/HS 

0.45 inch pitch w/HS 

Air speed at DIMM mid-point ranges 0.98m/s to 1.42m/s

• The DDR3 RDIMMs are designed to include an “optional” 

thermal sensor 

� Thermal sensor datasheets are available for one at least the 

vendor 

� The sensor may be a discrete near the PLL/Register device, 

or included within the SPD on the back side 

4/12/2007 29 



4/12/2007 30 



• The thermal sensor provides real time feedback through 

the module event pin, and/or the SMbus 

• This allows the memory controller to monitor the 

temperature of the module and “throttle” back if critical 

thermal limits are approaching 

• This is much like the thermal sensor on the AMB for the 

FBDIMM


4/12/2007 31 


Agenda 


• Possible Solutions 


Micron Thermal Tools and System Development 

• Micron has many resources to help make your design a 

success 

� For example, one of our wind tunnels 

4/12/2007 32 


Micron Thermal Tools and System Development 

• We offer thermal models of our components and some 

modules 

• We do custom heat sink designs for many high bandwidth 

applications 

• We can help to estimate your memory power budget using 

the Micron DDR3 Power Calculator 

4/12/2007 33

DDR3 Thermals - Micron

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