The specs on these chips aren't released, but previously Intel has quoted latencies around 1/2 DRAM speed (many orders of magnitude faster than SSDs).

These are byte addressable - they will look like RAM to the OS. (If you have a motherboard that supports them, there is a slight change to the spec).

To the application developer, the interface will be http://pmem.io/pmdk/ . Last I looked, there were several ways to do things, but the most commonly used would basically be allocating a chunk of memory and assigning it a file name so you could re-open it next time.

This is exciting because it could open up exciting possibilities like zero-CPU IO with DMA straight to persistent memory, "sleep" mode that is essentially free, re-thinking paging in modern operating systems, and generally re-thinking everything we've assumed since core memory.

On the same day we are talking about WASM microkernels in another thread. Things are getting fun again :)

> On the same day we are talking about WASM microkernels in another thread

That would be https://news.ycombinator.com/item?id=17187384

> but the most commonly used would basically be allocating a chunk of memory and assigning it a file name so you could re-open it next time.

So the PC platform finally caught up with Amiga's RAM disk ;-)

I think you meant RAD: disk... RAM disks don't survive a warm boot, but RAD did (IIRC). But, even RAD: didn't survive a cold boot (where this Optane memory does)

Still, I do fondly remember my Amiga days!

Intel's trying to keep the performance numbers under wraps for at least several more months. My predictions: write performance for a single Optane DIMM will be less than an order of magnitude better than an Optane NVMe SSD, maybe only twice as fast. Read latency might get close to that of slow DRAM, but you'll still notice that Optane is slower.

I wonder if Intel is trying to keep the endurance number under wraps. If they can't beat the current drive writes per day spec it is like having a 10 gigabit internet connection but a usage cap of 1 gigabyte.

Endurance should be fine, orders of magnitude better than flash. Just some temperature wear.

But the speed and density seems to be a problem. E.g. it's still 2x slower than DRAM, but theoretically should be faster. It could also have 3 bits, not just 2.

Linus did a video about Optane I found helpful.

https://youtu.be/cwy4ujt0qHM

This video is about the Optane devices you place in M2/nvme slots to be used as cache.

It will be interesting to see the real benchmarks on this DIMMS. We all want to know if they're comparable to real DDR4 memory.

The current market is terribly overpriced (there's some debate on if there's price fixing with the big three or if it's a genuine shortage/supply problem with the Note recalls and new phone releases). DDR4 is nearly double the price it was the last time I did a build over a year ago. :-/

EDIT: Looks like these chips will be specialized for certain server boards/CPUs and only share the DIMM interface and not protocol.

Thanks for the clarification, I'm watching the video now and it's interesting (Optane is way cheaper than I expected) and still seems useful as a lower bound for what we can expect from the DIMM version.

Thanks for the link! The Blender benchmark is really telling. Using Optane M2 modules as a swap disk allowed to run a task that required 12GB on a system with 4 GB of RAM and it took just 1.8 more in time then the native RAM case. So I guess I can put those Optane modules into a laptop with 16GB of RAM and run a calculation that requires 64GB of memory and it will be much cheaper than a laptop with 64GB of RAM.

But what is the price difference between an Optane module and the equivalent size of RAM?

This is not the Linus I was expecting.

hehe .. indeed, the Linus you were expecting would have been a mailing list post.

What saves the page table between reboots...the OS must have specific support for this surely...?

You're still going to have some DRAM attached to your CPU, too. The non-volatile portion of the address range is probably going to be managed with a filesystem that supports DAX.

Wait...so is this about having an ssd on the memory bus...or non-volatile paged memory?