Single-Chip DIMM To Replace Big Sticks of RAM

MrSeb writes "Invensas, a subsidiary of chip microelectronics company Tessera, has discovered a way of stacking multiple DRAM chips on top of each other. This process, called multi-die face-down packaging, or xFD for short, massively increases memory density, reduces power consumption, and should pave the way for faster and more efficient memory chips. Multi-die face-down packaging is exactly what it sounds like, with memory dies stacked on top of each other like roofing tiles. Much like a normal desktop DIMMs and laptop SO-DIMMs, each of the stacked dies is wired to each other in series — but in this case, the connections are much shorter, as they only have to run a few micrometers to the chip below it. This is where all of the power and speed enhancements come from: shorter interconnects mean less power is needed (and thus less heat is dissipated) and signals propagate faster."

Comments

Patent Licensing

[TheReaperD]

The questions is, will the patent fees be reasonable enough that we will see this technology for less than $200 a DIMM?

Re:Patent Licensing

[Baloroth]

Patent fees? Why would Tessera charge itself patent fees? I think you have been staring at software patents too long.

They may or may not license this to other companies, and once they start building them they will have to have low enough prices to be competitive with existing DRAM technology. The world of hardware is not quite like the software world where companies routinely submarine others in areas they often don't even make product. In hardware, you can patent an excellent technology, but you either have to build it yourself or license it for affordable rates to actually make money off it. Unlike software where you can look at someone else's product, patent it, then sue their asses off and get a settlement. AFAIK that has never worked in hardware (it probably has, but it is certainly much, much rarer.)

Re:Patent Licensing

[TheReaperD]

Though I have been following software patents closely, it has no bearing on my question/comment. One of two things will happen, they will either license this to other vendors for a fee where they can manufacture it or they will not and only build them themselves. If they license it, they can charge a fee that is either reasonable or exorbitant. If they build it in house they can charge whatever they want. Though either option is their right, I, as a consumer, would like to see this product come to the consumer market at a reasonable price, thus my question/comment.

And no, they do not have to be price competitive to make a profit. This has been proven many times over. Since they have, according to TFA, a superior product, they have the option of producing it in low volume and charge a high price for the high end server and gamer market. If you insist on a citation, just look at Apple. They produce in low volume, charge a high fee and make a large profit because their customers believe they make a superior product. And I don't have to agree with it for the last sentence to be true.

This invention means jack to me, as a consumer, if they take the Apple route. Thus, my original comment.

Re:Patent Licensing

[dgatwood]

Wasn't the licensing fees. They were never all that expensive.

USB is so ubiquitous in large part because the silicon for USB devices is much, much simpler, and thus much, much cheaper. USB devices can be dumb as a post, whereas FireWire devices have to actually understand a lot more about the bus topology, etc., IIRC.

Also, there's no such thing as a slow FireWire bus. S100 is the bottom limit. Therefore, it isn't a great match for really trivial devices like mice and keyboards.

Also, Intel supported USB very quickly, and drug their heels on FireWire until... well, I'm not sure if they've ever shipped a southbridge with integrated FireWire.... So for computer manufacturers, FireWire was an extra part that they had to pay for, not just an extra connector.

And there were no doubt other factors. I'm not convinced that the licensing was a significant one, though. By 2001, it was something on the order of a quarter per device. I think that's less than a tenth what the actual silicon costs. Even back when it was a dollar per port, it was still a tiny cost compared with the silicon.

Re:Patent Licensing

[spauldo]

Rambus did the hardware patent troll thing. It was all over /. back in the day.

Short story, Rambus was a member of an industry group designing the new RAM chips (SDRAM, pentium II and III era). The new designs used technlology they had patented, but this wasn't a big deal since all members of the group were supposed to license any applicable patents they held under "reasonable" terms.

Rambus didn't like that, so they pulled out and started suing everyone who made SDRAM. Intel had started using Rambus memory modules on their motherboards (RDRAM), and had already committed to the designs before all this broke out. The lawsuits were all over the place, and Rambus was found guilty of fraud, had the ruling overturned, was sued by the FTC for antitrust violations, and so on.

The whole thing was covered by /., and it went on for years. Only the SCO debacle topped it.

How are they handling the heat?

[jandrese]

The problem with stacked chips like this in the past has been cooling the wafers in the middle of the stack. While DIMMs don't run as hot as processors or GPUs, this is still a concern for them. I wonder how they're going to handle this? Or are they only going to target low power low performance parts?

Unlikely

[vlm]

The marketing release implies most of the power is being dropped resistively in the leads instead of in the dies. Just doesn't work that way.

Think about it for a second... The voltage on the die is only a tiny bit less than the voltage on the bus... You know the bus impedance too so that gives away current flow. Do a little ohms law on that tiny little drop and the tiny little current and compare it to what the die drops.

Or look at it from a thermal engineering perspective... they put heatsinks on the dies, not on the leads...

Now there will be some savings, probably lower capacitance and inductance and all that makes life easier for the bus drivers. But you're still gonna roast the dies in the middle of the sandwich. So you got three charcoal bbqs stacked on top of each other. No matter how fancy you make the cooking grate the burgers in the middle are gonna fry even if the guys on the end are raw ...

Re:DIMM == dual in-line memory module

[Artraze]

Yes, DIMM is referring to the board form factor, not layout. Specifically, they are dual because the gold fingers on each side have independent signals, while SIMMs have the same signal replicated on each side.

Re:DIMM == dual in-line memory module

[jd]

DIMMPLE? (DIMMs in a PiLE)

Re:Stacking RAM is not new.

[gstrickler]

But doing it inside the package, directly stacking chip on chip has significant advantages over stacking packages. Lower height, better heat dissipation, shorter interconnects, etc. And if the chips are designed such that they share the drivers, buffers, & latches, etc for the external connection, that can save quite a bit of power. There are many things you can do in package, that are impractical or impossible off package.