61–70 of 85 posts
Earlier quoted context omitted.
These days that bulk of us people doing dev work aren't getting to play in the actual DC, it's all so abstracted away. Frankly looking to get a used rack or two at home here, just so I can play with the HW a bit. (I do embedded and not server stuff mostly these days anyways, but generally interested in systems stuff, so)
I was talking with a colleague about this just the other day. We all used to have home labs, because we could get reasonably near to what business used and learn that way. Now, what goes on in is so different, frankly you won't learn much with one. Obviously if you're just interested then go for it. It's just not practical generally speaking.
It's been a long day, managed to take a few seconds wondering what this interesting new "best CPUs" technical architecture was before realizing the article is SEO'd blogspam. Maybe switch to the source article? https://www.servethehome.com/fadu-cxl-2-0-switch-and-pcie-ge...
The slowest clock speed for DDR5 is 2,000Mhz or 0.5ns per cycle. At 2/3c, electricity should be able to travel about 10cm max in one cycle. I suppose 4Ghz RAM would be only 5cm. Is having an external unit with much greater than 10cm of copper travel ultimately a limiting factor here with modern day RAM speeds?
This is not exactly the reason, but trace length/loss is a major problem. Laptop SODIMMs are already severely limiting DDR5 bandwidth, server/desktop DIMMs are getting close. Users aren't gonna like it, but unswappable packaged RAM is coming to most CPUs.
Earlier quoted context omitted.
I was talking with a colleague about this just the other day. We all used to have home labs, because we could get reasonably near to what business used and learn that way. Now, what goes on in is so different, frankly you won't learn much with one. Obviously if you're just interested then go for it. It's just not practical generally speaking.
For myself, I've got 3gbps fiber to the house, and a need to host something. Pondering buying a used server instead of dishing money out to AWS or GCP. Question is if the power bills make sense.
Just today, I replaced the whole thing with a single mini PC with a laptop Ryzen chip (6900HX). Pulls like 60W at the wall under load.
This is a circuitous way of saying that, for non-mission critical stuff, you can self-host and save a ton of money over the equivalent hosted option. You don't even need server hardware necessarily, depending on what you're trying to learn from the experience. Standard caveats about securing your home network apply.
(Note: I'm not actually seriously saying a 16x blade server and a mini PC are equivalent. I got the blade server to learn things (more networking, mostly), it was very, very overpowered for my workloads)
CXL is useful for many more things beyond just memory expansion (which is a "type 3 device"). The purpose of CXL is to allow for memory coherency between different CXL devices. To quote the spec on type 2 devices: > CXL Type 2 devices, in addition to fully coherent cache, also have memory, for example DDR, High-Bandwidth Memory (HBM), etc., attached to the device. These devices execute against memory, but their perfo…
CXL for Persistent Memory, as the Optane successor (or rather, sole-survivor if you will) is what excites me. Persistent Memory databases are such a neat idea, it's a shame that the hardware for it isn't commonplace.
wasn't Optane (hardware) trying to use CXL?
Earlier quoted context omitted.
This is not exactly the reason, but trace length/loss is a major problem. Laptop SODIMMs are already severely limiting DDR5 bandwidth, server/desktop DIMMs are getting close. Users aren't gonna like it, but unswappable packaged RAM is coming to most CPUs.
What do you mean by packaged RAM and what protocol does it use that would be faster than DDR5?
Depends. Apple uses LPDDR5X on a cheap substrate, which is basically just RAM chips soldered to a tiny motherboard, and that is already very fast. But it could also mean HBM on an expensive interposer or cheaper Intel EMIB, or something like Samsung's proposed Wide I/O, or even something new like stacked RAM with TSVs.
CPU/RAM packaging is getting increasingly complicated.
> what protocol does it use that would be faster than DDR5
Depends, but it can just be straight up DDR5. SODIMMS are terrible because they need 1.35V (vs 1.1V stock DDR5) for really slow speeds and terrible ram timings, while soldered DDR5 and LPDDR5X do not. The closer the DDR5 gets to the CPU, the faster, more power efficient and lower latency it gets.
Earlier quoted context omitted.
The article seems to reference having external AI etc accelerators colocated with the RAM they use, but then tied to a host machine via CXL. So that makes a certain amount of sense. Latency sensitive stuff happens co-located with the RAM, and then you just take advantage of throughput back to the host. I'm personally now imagining a specialized database appliance which takes the role of the whole of the pager and buf…
I just finished my master’s thesis on database buffer management with CXL [1]. It’s not published due to confidential hardware information, but we are working on a paper. [1] https://hpi.de/rabl/teaching/master-theses/ongoing-masters-t...
For some reason the whole issue of buffer mgmt is something I nerd out on a bit.