XBox 360 eDRAM

[arhra]

Can you go into more detail how MCM tech works? Obviously on the PCB, placing 1024 wires between two chips is crazy. But what element of MCM tech solves this?

AFAICT (i'm in no way an expert in chip packaging technology, and most of the available material assumes you are), MCM packaging basically just places multiple dies on the same substrate (the bit that takes the connections from the die and provides a way for them to attach to the underlying pcb), which can have an extremely high interconnect density, compared to pcb wire density. Then the only connections needed to the PCB are the external IO connections, not the connections between the two dies on the MCM.

There's no doubt there's a bit more to it than that in reality, but that seems to be the general idea. Unfortunately most of the documentation about MCM packaging methods consists of industry reports, academic articles, and the like, and most of it goes right over my head

 

[aaronspink]

Can you go into more detail how MCM tech works? Obviously on the PCB, placing 1024 wires between two chips is crazy. But what element of MCM tech solves this?

Packaging basics:

A package considers of a substrate material (generally either a ceramic or an fiber composite), multiple layers of signalling, a board level interconnect (either lands, bumps, or pins), and a die level interconnect (bumps).

Most dies currently have several thousand to several tens of thousands of bumps. The bump sizes that connect to the board are generally 10x bigger in critical dimensions than the bumps that are on die.

So die side a thousand bumps isn't a big deal, but board side it is very significant. Take a look at say a socket 939 or socket t processor. Lots of area on the package just to get all the signal pins/lands there

So basically, you can just do things smaller in package than out of package. And substrate size has a large factor in substrate cost.

Aaron Spink
speaking for myself inc.

 

[PC-Engine]

Does Xenos uses stacked packaging like the picture below?

 

[Geeforcer]

So Dave,

It has been almost a week since you started this thread and made that proclamation. Have you been able to clarify it since then?

 

[Pete]

I suspect his upcoming Xenos article/interview will reveal all (that he's willing to reveal, being the professional tease he is).