PCIe RAM?

[vanished]

So I was thinking, the transfer speed of DDR3-1600 is supposedly 12800 MB/s (12.5 GB/s), and 16 lanes of PCIe 3.0 has a speed of 15.75 GB/s... so, could (in theory) a PCIe card exist that has DIMMs on it which allow you to plug in more RAM?  The bandwidth seems to be sufficient...

 

Thoughts?  :rolleyes:

[79wjd]

The latency to the PCIE lanes is higher than the latency to memory (I believe, and ram cares more about latency then throughput for the majority of workloads).

[daniellearmouth]

There exists PCIe cards that allow you to plug DIMMs in. From what I'm aware, though, they're generally used as a RAM disk.

[8-Bit Ninja]

I don't see the point, some motherboards have 8 dim slots which is more than enough.

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[Glenwing]

That's basically what already happens when a GPU runs out of dedicated memory and accesses the system memory, just in the reverse direction.

[vanished]

I don't see the point, some motherboards have 8 dim slots which is more than enough.

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Some have 16, or even more (multi-socket boards).  I just wanted a discussion about it, regardless of if it's "necessary"

[thekeemo]

Because that is just one stick

Meaning you can have a maximum of 8gb extra PER full length x16 pcie slot

[cooky560]

Isn't pci-e slower than direct memory access?

[incarnate]

Isn't pci-e slower than direct memory access?

Kinda, it has higher latency so it takes longer to start reading or writing. Which is fine for graphics cards and ssd's, but system memory is far more sensitive to latency

[Footy]

The next big thing is going to be HDDs and Ram being combined...

http://newsroom.intel.com/community/intel_newsroom/blog/2015/07/28/intel-and-micron-produce-breakthrough-memory-technology

[vanished]

Because that is just one stick

Meaning you can have a maximum of 8gb extra PER full length x16 pcie slot

Good point.  But I guess we already knew it wasn't practical... just curious if it would work

 

Isn't pci-e slower than direct memory access?

Well, if my calculations are right, then no, PCIe is actually faster (in terms of bandwidth), but as a few people have mentioned, it does have higher latency, so it would be impractical for certain applications (like sanding in for system RAM I guess )

 

The next big thing is going to be HDDs and Ram being combined...

http://newsroom.intel.com/community/intel_newsroom/blog/2015/07/28/intel-and-micron-produce-breakthrough-memory-technology

That would be cool... no more differentiation between "storage" and "memory"; just buy one device and allocate as much as you need to both

[Fetzie]

There are daughterboards for servers that have lots of RAM slots, but I'm pretty sure they'd use a proprietary connector.

[Mattyd7829]

its a shame that no-one has thought of a way to increase graphics ram by utilizing extra pci-e slots

[Fetzie]

its a shame that no-one has thought of a way to increase graphics ram by utilizing extra pci-e slots

 

There's a very good reason they cluster vRAM chips as closely around the core as possible