r/hardware • u/Emerson_Wallace_9272 • 2d ago
News First MRDIMMs are to come out - friggin 12800MHz. At 2x capacity
Yes, this stuff is for servers, but it is god given solution for off-the-shelf APUs, which are staved for bandwidth.
Some go for LPDDRx, but that kills expandability and capacity.
This seems to solve all that and then some. It is effectively a speed doubler - it combines 2 sets of chips ( that would complete ordinary UDIMM stick) in a "RAID0" way - it interlieves them. Special high-speed "register" chip on M/C/RDIMM takes care of all that: unloading the data lines for optimal transfer speed, doubling the speed over the bus, registering and de/multiplexing data stream and serving TWO banks of RAM.
BTW, 12.800MHz is just the start. This thing is poised to reach much higher. 18000 MHz wouldn't surprise me.
Looks like win-win-win-win all around. Only downside is that de/multipexer/register introduces extra 1 CLK latency. But at DDR5's existing latencies, that is going to be negligagble, I reckon.
It'd be so awesome if we could see AMD's APUs using this. Along with 3D cache on UDNA1, that extra bandwidth would make whole thing shine brightly not only for gaming and CAD, AI would benefit from it, too.
But AMD wouldn't be AMD if it hadn't missed that boat, too...🙄
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u/SteakandChickenMan 2d ago
Why should AMD build datacenter memory IP into a laptop chip? There’s next to 0 business case when regular LPDDR5X is at 9600+ over that thing’s lifetime.
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u/Emerson_Wallace_9272 2d ago
LPDDR5 can't be socketed,replaced or expanded etc. It was meant as economic, lower power solution. Its capacity is quite limited.
9600 speed bump is just an evolutive step with perceptible speed uplift, not a qualitative change.
People like and are prepared to pay APU with great bandwidth and capacity. Strix Halo systems are proof for that.
Well, if you did similar transformation to DDR5 system, you'd get 16.800 MHz ( double the existing, solidly fast 8400MHz chips) on a MRDIMM of 2x size- so 48GiB per stick. With four-channel APU that'd give you 192GiB of DRAM. Almost at GDDR6 transfer rate speeds.
On a small APU that fits on a mini-ITX or uATX MoBo.
But as fast 64 GiB UDIMMs are just around the corner,you could get 512GiB on a Strix Halo counterpart easily, just with MRDIMM stick change.
Who wouldn't like that ?
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u/iDontSeedMyTorrents 2d ago
Who wouldn't like that ?
Whoever has to pay for it.
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u/Emerson_Wallace_9272 2d ago
Why ? People are paying pretty steep price premium for Strix Halo right now.
All because it's an APU that can access 128GiB RAM at great bandwidth.
So, it you offered beffier APU that can do 512GB, market would reject it ? Just for the price of extra DRAM ? But DDR5 is by far the cheapst of all of them per GiB.
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u/RZ_Domain 2d ago
LPDDR5 can't be socketed,replaced or expanded etc. It was meant as economic, lower power solution. Its capacity is quite limited.
Might wanna check your calendar and make sure it's not on 2010 buddy, LPCAMM2 exists. But if OEMs aren't adopting that, what makes you think they will adopt MRDIMM for regular consumers?
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u/Emerson_Wallace_9272 2d ago
I did.\ LPCAMM2 exists, but barely. No one cares that much ATM.\ And almost no one uses it.
Also, it isn't any faster than UDIMM at present. Which is a big bummer for a product that was to be a speed screaming monster.
Looks like it was just a first step that could be rethought before industry reinvents RAM sticks.
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u/Exist50 2d ago
I did.\ LPCAMM2 exists, but barely. No one cares that much ATM.\ And almost no one uses it.
It's new. It will get much better adoption next year. But MRDIMMs are basically in the same boat, so...
Also, it isn't any faster than UDIMM at present
Stock LPDDR is not faster than XMP/EXPO UDIMM, but what about when LPCAMM gets the same treatment?
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u/Emerson_Wallace_9272 2d ago edited 2d ago
I'm skeptical about LP/CAMM2.
Great idea, but so far shitty execution.
Few MoBos that were shown with CAMM2 look bad to me.
For some f**ED up reason even though modules is supposed by compression, everyone reserves the place for the whole CAMM2 module (so, not just the connector part) thus thoroughly wasting the PCB space.
It would be nice if we could see it combined with MRDIMM idea - using better transfer path with greater signal integrity that CAMM2 offers to utilize the transfer register/de/multiplexer chip, along with load decoupling, clock regeneration etc.
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u/schmintendo 2d ago
Not OP, but I thought the purpose for lpcamm was for laptops. It seems stupid to put it on desktops when it takes up space laying flat, but it's perfect for prosumer or enterprise laptops that need/want repairability.
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u/Green_Struggle_1815 2d ago
people on reddit think that, but it will never be a widespread thing in notebooks. too expensive and little demand for upgradability. Even as a 'tech enthusiast' i don't need it, i just buy the ram i need right away. I never upgraded ram on my desktop machines either.
To me this is mostly desktop tech where it will replace the Dimm slots.
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u/schmintendo 2d ago
It all depends on how much enterprise customers are clamoring for repairability honestly. I think you're right that it won't take off for gaming laptops unless it gets cheaper (which is kind of a chicken or the egg thing) but I would think large corps would value being able to replace RAM. Right now we have to RMA the whole ass motherboard from a laptop if it has a memory error, which costs the OEM quite a bit.
This will probably be more important once hardware that requires super fast memory is mainstream, you can still get dimm slots on most lower end corporate devices.
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u/Green_Struggle_1815 2d ago
i mean even on non budget devices like apple mac books people suck it up and apple laughs about being able to easily upsell the better model and saving on bom cost.
Our IT Dept would probably prefer non upgradability because less work for them as they can answer every upgrade request with 'Just order a new one'
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u/Green_Struggle_1815 2d ago
upgradability is a non concern for mass produced commodity products.
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u/Emerson_Wallace_9272 2d ago
There are plenty of subreddits, proving exactly otherwise. This one included.
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u/Ghostsonplanets 2d ago
Subreddits are the literal definition of vocal minority. The vast majority of consumers don't care or are concerned about the possibility of upgrades. See who are the best selling eletronics every year.
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u/Emerson_Wallace_9272 2d ago
Minorities are usually relevant. Majority is sea of walking meat.
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u/Green_Struggle_1815 2d ago
If a market is big enough to generate enough revenue/profit to justify releasing a product for it, it will happen sooner or later. I'm sure there will be LPCAMM2 notebooks, but they will be the exception not the standard.
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u/Ghostsonplanets 2d ago
Most companies aren't going to base their decisions on minority desires though.
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u/Emerson_Wallace_9272 2d ago
Neither APUs nor ThreadRipper etc were even a thing before AMD introduced them.
It will happen. It just needs a solid product.
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u/SirActionhaHAA 2d ago edited 2d ago
LPDDR5 can't be socketed,replaced or expanded etc.
That ain't a problem. The apu market exists only for mobile and consoles, anything desktop is far cheaper and easier with a dgpu. Idk why anyone would be obsessed with the idea of a desktop apu, it increases costs and complexity in exchange for portability which the desktop form mostly doesn't need. Why have the gpu and cpu on the same socket and increase cooling problems? For mini pcs? How much of the market is that?
- Mobile: lpddr due to power efficiency
- Desktop: dgpu, nobody cares about diy large apu
- Dc cpu: mrdimm (yea this is where it's useful and comes with zen6, it's how they would achieve 1.6tb/s on 16 channels)
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u/AntLive9218 1d ago
Desktop doesn't cover only gaming setups though, there are still tons of office desktops which could benefit from better iGPU performance. A decent APU isn't just for portability, the whole segment ended up displacing low cost dGPUs as iGPUs got good enough for a lot of basic tasks, they are just often bandwidth starved.
You are right though about it being a pain in the ass in many ways:
Even desktop CPUs are bandwidth starved currently, so it would take a whole lot more increase to have extra room for other needs.
Bandwidth alone isn't the only problem, extra traffic also comes with latency problems which is a significant issue for compute.
Unfortunately iGPUs typically come with odd quirks, especially AMD ones. Compute tasks have tons of issues with them, even when not used directly, like ROCm even documenting problems of the iGPU simply being visible causing problems, which I've observed too.
I like the idea of some good APUs being around though for office/browsing setups, and theoretically just adding a higher performance GPU chiplet to some products in a lineup should be cost efficient, packaging is just possibly not mature enough to make it worthy.
I'd understand though if the mentioned use cases are already pushed towards more expensive laptops even if mobility is not required, just to have less products. But then that's an artificial limitation, and I found it interesting how Chinese "desktop" motherboards with "laptop" CPUs made fun of it.
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u/SirActionhaHAA 1d ago edited 1d ago
Desktop doesn't cover only gaming setups though, there are still tons of office desktops which could benefit from better iGPU performance.
Majority of the "office" or enterprise desk machines don't require heavy igpu perf, they are pcs that run stuff like excel. Even if you do, a large igpu is still more costly than a cpu + dgpu at the 30cu size, so idk why anyone would try to justify that form factor. People probably thought that dgpus are costly because of the "gamer tax" coming from huge triple fan or lc designs
Remember that the biggest difference between a dgpu and large apu systems are the memory config and size. Neither are needed for the average enterprise desktops. Amd's strix halo is proof of that, none of the strix halo devices are less costly than dgpu laptops with the equivalent perf.
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u/nisaaru 1d ago
Only gamers and AI people need a dGPU on desktops. That's a minority.
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u/SirActionhaHAA 1d ago
Only gamers and AI people need a dGPU on desktops
And even fewer need a large igpu on desktop.
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u/nisaaru 16h ago
Nobody says anything about the size of the gpu in an APU.
What do you think all the ARM Apple systems in iphones, ipads, mac, macbook and macminis are using? APUs with different CPU and GPU configs. One of their performance advantage over PC's CPU and dGPU setups is closely connected wide bus memory soldered next to the APU and no memory shuffling between CPU and dGPU. A system with low latency, unified cache coherency and huge bandwidth at far lower power requirements.
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u/Emerson_Wallace_9272 2d ago
The apu market exists only for mobile, anything desktop is far cheaper and easier with a dgpu.
RLY ? 8700G can be had for less than a $400 with MoBo and RAM. In Mini-ITX form.
Now try to do that with 8-core, MobO and gGPU.
Cheapest dGPU is $150 and it doesn't match 8700G.
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u/SirActionhaHAA 1d ago edited 1d ago
Cheapest dGPU is $150 and it doesn't match 8700G
The lower ya go the cheaper it is for apus due to the difference in bom costs (separate gpu board, memory etc). We're talkin a large apu here and not a 12cu low profile 6400. Push the cu count up to the 30s or 40s and an apu starts to cost more than a dgpu system due to wider memory bus (required to avoid bandwidth bottlenecks), heat density problems (imagine cooling a 9060xt+ dgpu and a 9950x on a single socket, >300w tdp yikes), and reduced yields from a larger monolithic die
Op wants a large desktop apu the size of strix halo, not a 12cu tiny mobile apu. That's the whole point of this post, large desktop apu bad, small apu good.
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u/Emerson_Wallace_9272 2d ago
Look at Strix Halo. It has caused quite a stir on desktop, too.
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u/SirActionhaHAA 1d ago
It has caused quite a stir on desktop, too.
That's an overstatement. Nobody is buying a halo system for the perf/dollar reasons. It usually falls behind an equivalent 4070 mobile laptop in perf and price. Ya wonder why amd didn't market it as a gaming chip and went ai route instead? It's because the lpddr capacity advantage is the only thing it's got over a dgpu system. This is proven by dozens of laptop comparisons.
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u/Verite_Rendition 2d ago
Just so it's noted, the first MRDIMMs are already out. And have been since the launch of Granite Rapids (Xeon 6xxxP) last year. Those guys support MRDIMMs at up to DDR5-8800 speeds.
https://www.crucial.com/memory/server-ddr5/mtc40f4086s1hc88xd1r
There are no published plans to bring them to consumer desktops, unfortunately.
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u/zoson 1d ago
*12800MT/s, not MHz. 12800MT/s DDR5 runs at 6400MHz.
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u/Exist50 1d ago
Since Hz is just events per second, you could interpret it as transfers instead of clock frequency. Just semantics.
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u/zoson 1d ago
Hz in Signals and Systems is defined explicitly as the frequency at which the signal oscillates between high and low states.
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u/Exist50 1d ago
Hz as a unit is literally just [1/s]. Doesn't specify what the event in question is. Yes, there are conventions depending on use case, but I'd argue that for advertising DDR speed, the convention is transfers.
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u/airmantharp 1d ago
It’s not that you’re wrong, but rather that DRAM is then hooked up to a bunch of stuff that uses the main signals and systems convention, which is why MT/s started to be used instead for clarity
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u/Exist50 1d ago
I don't disagree with using MT/s for clarity, but practically speaking, anyone who knows the difference can trivially infer that 12800 is referring to MT/s, and anyone who doesn't is probably used to seeing MHz used interchangeably with MT/s.
So the "correction" is both wrong from a strictly pedantic perspective and pointless from a practical one. Thus I don't see why one would bother bringing it up.
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u/zoson 21h ago
OP incorrectly said MHz. The article never does. Correct is correct and wrong is wrong.
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u/Exist50 19h ago
OP incorrectly said MHz
As I just pointed out, even if you want to be pedantic, MHz is not incorrect.
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u/zoson 19h ago
Except, it is, and as explained to you already more than one person. The incorrectness of saying MHz is the entire reason why MT/s became a thing. Being able to infer what is correct does not change the fact that the stated units are incorrect. You are technically incorrect. The worst kind of incorrect.
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u/Exist50 19h ago edited 19h ago
Except, it is, and as explained to you already more than one person
No, as I've already addressed. Maybe try reading comments before replying to them? Hz is a unit. It does not solely apply to clock pulses. If you're going to try arguing semantics, at least learn what the terms you're using mean.
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u/WolfishDJ 1d ago
You'd be better off running LPCAMM2 if you got your hands on the modules imo. Upgradable but it runs faster than typical DDR5 because they're using LPDDR5/X based memory at much higher Mhz.
Lenovo has some workstation laptops currently that run LPCAMM2
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u/Emerson_Wallace_9272 1d ago
LPDDR5 doesn't have that much higher frequencies. And it has higher latency, so it's a tradeoff.
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u/tecedu 1d ago
AMD hasn't even done on Epycs, why would they do for APUs?
MRDIMMS are also insanely expensive, like they at minimum 1.8x the cost of 6400mhz ecc ddr5 which is already expensive?
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u/airmantharp 1d ago
AMDs APUs are in a weird place; one that may or may not be unique going forward, depending on their own efforts and the efforts of their competitors.
If AMD keeps pushing the limits of their APU configuration, they might well find MRDIMMs to be ‘relatively’ cost effective IMO.
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u/Pillokun 2d ago
I might have a brain damage right now this saturday morning as I just cant put your text into any context. but too me this is not anything to do with frequency ie 12800mhz, it is like 3200mhz x2 = ddr = mega transfer/s x2.
the sticks would still only run at 3200mhz at the double data rate.
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u/NerdProcrastinating 2d ago
How it works:
- Processor memory controller <--- 6400 MHz DDR (12800 MT/s) ---> MRDIMM buffer chip
- MRDIMM buffer chip <--- 3200 MHz DDR (6400 MT/s) --> 2 x "mux ranks" of DDR5 DRAM chips
i.e. the requests run in parallel on both mux ranks and the buffer chip interleaves the data bit-by-bit.
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u/Emerson_Wallace_9272 2d ago
No, register level on the stick adds (among other things) another doubling on top of that DDR doubling.
SO you have two sub-sticks on the same MRDIMM stick, which each other transfer heating each "sub-stick". Somewhat what RAID-0 does with disks...
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u/mckirkus 1d ago
There are not a ton of memory bandwidth limited use cases. HPC/CFD, finance, etc and a lot of the memory bandwidth limited solutions are getting ported to GPUs that have 1-2 TB/s via HBM.
I have a 12 channel Epyc rig for computational fluid dynamics and it's something like 500GB/s at DDR-5 48000. It gets memory starved around 64 cores.
So if I had 192 cores this would be welcome but most just get 2x CPU setups that effectively have 24 memory channels.
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u/chapstickbomber 22h ago
Soon we will say goodbye to MHz and welcome our new double digit GHz overlords
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u/ResponsibleJudge3172 2d ago
The theoretical max of DDR 5 back then was estimated to be 12800MHZ. We are quickly closing in on this
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u/bigvalen 2d ago
Heh. 12800 is 12.8GB/s, no 12800mhz. Which would be impressive. It is probably 1600Mhz, but 8 byte bus, so 12800.
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u/Emerson_Wallace_9272 2d ago
Nope.It's 12,800 gigatransfers per second peak transfer theoretical maximum. Each transfer is 8 bytes, so this means roughly 100GB/s theoretical peak. Per stick/channel.
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u/Jumpy_Cauliflower410 2d ago
Who pays decent money for APUs? Why would I buy some expensive APU+ memory solution when I could have a CPU+GPU combo and have better performance?
They "miss the boat" because they have better opportunities. The only viable "large" APU are consoles.
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u/ThisAccountIsStolen 7h ago
Why would AMD add support for a multi-thousand dollar memory solution to APUs—which are generally geared toward the budget segment—where a full gaming GPU isn't needed?
Spending $2000+ (that's based on the pricing of the current 8800MT/s MRDIMMs that are already on the market) just on RAM for an APU in the budget segment makes absolutely zero sense no matter how you try to spin it.
It would be cheaper to just add a 5080.
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u/FragrantGas9 1d ago
That’s Mr. Dimm to you.