Breaking News
Comments
Newest First | Oldest First | Threaded View
Peter.Barratt
User Rank
Rookie
re: SMART Modular Technologies Design Feature: Stacking solves DRAM supply challenges and unique application requirements
Peter.Barratt   9/15/2010 2:50:50 PM
NO RATINGS
I have been involved in stacked DRAM products on the supplier side since the early 80's. While the concept is quite viable, there are some points to consider. 1. Addressing. DRAMS use each address pin for two address inputs. When you double the density, you need a 1/2 pin more addressing. Either the memory module or the system must provide for the. 2. Fanin/fanout. By stacking, you at least double the drive requirements and the output loading of the module. If you add a buffer chip to take care of this, you add delays. For a buffered module, it's usually a clock cycle worth. 3. Cooling. The added height of the DRAM stack may interfere with the air flow over the module. 4. Cost. Cost is more than 2X the original because of the stacking costs, additional testing, any support chips, etc. 5. Source control. Module manufacturers can buy from a plurality of DRAM vendors making the control of vendor source and die revisions more difficult. 6. Reliability. There are more interconnections and 2X the number of die involved. All that being said, stacking is sometimes the best or only way to go.

ttt3
User Rank
Rookie
re: SMART Modular Technologies Design Feature: Stacking solves DRAM supply challenges and unique application requirements
ttt3   9/14/2010 3:32:20 PM
NO RATINGS
I should add that the parts I had experience with were Virtium chip stacks (not SMART), so I'm not sure if this applies to all manufacturers.

ttt3
User Rank
Rookie
re: SMART Modular Technologies Design Feature: Stacking solves DRAM supply challenges and unique application requirements
ttt3   9/14/2010 3:30:56 PM
NO RATINGS
I am intimately familiar with the stacked TSOP DDR DRAM. I can say we've seen a high rate of manufacturing defects related to these parts - particularly, loose solder joints and shorts on the pins, and issues with the interposer PCB between the top and bottom chips in the stack. These stacked TSOPs are very hard to rework/repair when closely spaced together.

resistion
User Rank
CEO
re: SMART Modular Technologies Design Feature: Stacking solves DRAM supply challenges and unique application requirements
resistion   9/14/2010 2:21:37 PM
NO RATINGS
I hardly see this as a solution to the stated problems but aggravating them. Stacking is indeed the best way to clear out old but well-established products to make way for newer ones. But Nx stacking is Nx cost and Nx interface complexity, and the yield is harder to meet (on a totally new product). If you can put more onto the same chip, that is still more cost effective. Sometimes, that is not possible - then you can stack.



EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Max Maxfield

Oh, No! My Antique Analog Meter Has Twitched Its Last
Max Maxfield
18 comments
Well, life is certainly full of ups and downs, isn't it? When it comes to the antique analog meters I'm using in a number of my hobby projects, things appeared to be going swimmingly well, ...

EDN Staff

11 Summer Vacation Spots for Engineers
EDN Staff
20 comments
This collection of places from technology history, museums, and modern marvels is a roadmap for an engineering adventure that will take you around the world. Here are just a few spots ...

Glen Chenier

Engineers Solve Analog/Digital Problem, Invent Creative Expletives
Glen Chenier
15 comments
- An analog engineer and a digital engineer join forces, use their respective skills, and pull a few bunnies out of a hat to troubleshoot a system with which they are completely ...

Larry Desjardin

Engineers Should Study Finance: 5 Reasons Why
Larry Desjardin
46 comments
I'm a big proponent of engineers learning financial basics. Why? Because engineers are making decisions all the time, in multiple ways. Having a good financial understanding guides these ...

Flash Poll
Top Comments of the Week
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)