I'm assuming this means that 6000mhz ram runs at 6000x32x2\8=48GBps?
RAM bandwidth calculator:
https://edu.finlaydag33k.nl/calculating ram bandwidth/
Is this bandwidth per modules or per pair of modules?
A bit complex to answer.
For DDR4, where there is one 64 bit channel for each DIMM, and when running one 3000 MT/s DIMM, bandwidth is up to 24 GB/s.
Add 2nd DIMM into proper slot, where you end up with dual-channel RAM (same 3000 MT/s speed), bandwidth doubles up to 48 GB/s.
For DDR5, each DIMM has two 32 bit channels. Making individual DIMM dual-channel off the bat. Where one 6000 MT/s DIMM bandwidth is up to 48 GB/s.
Add 2nd DIMM into proper slot, (2nd RAM channel on MoBo), making total bandwidth up to 96 GB/s.
If i have 2x48GB modules at 6000mhz is this 48 or 96GBps?
Depends on where you slot the DIMMs in.
If you put both DIMMs on Channel A on MoBo, you'd be limited up to 48 GB/s.
But if you put each DIMM into proper channel (as advised by MoBo manual), where one is in Channel A2 and 2nd one is in Channel B2, then you end up with up to 96 GB/s.
1. Does dual rank ram help access each channel separately or does it work independent of single/dual channel ram? Does it help access each chip or does it always double up separately?
Dual-rank (2R) is a DIMM that contains two distinct sets of memory chips (ranks) on a single DIMM, which the memory controller can access independently, potentially leading to increased density and bandwidth or lower latency, compared to single-rank (1R) modules.
Though, overall performance depends on the controller's ability to exploit this feature and the specific workload.
Also, you can't see dual-rank by viewing DIMM modules alone, since memory chips can be both sides of the DIMM but RAM is still 1R, rather than 2R.
And does any ram combo go over this?
Yes.
DDR5 also has higher frequencies than DDR4, up to 9600 MT/s is currently possible, 8200 MT/s translates into around 120 GB/s of bandwidth. Speeds of up to 13,000 MT/s have been achieved using liquid nitrogen.
Source:
https://en.wikipedia.org/wiki/DDR5_SDRAM
Is there a limit of 80GBps on am5 cpus like the 9950x3d?
No.
For example: MSI X870E Godlike specs:
https://www.msi.com/Motherboard/MEG-X870E-GODLIKE/Specification
If you look the supported RAM conf and speeds, you'd see that;
1DPC, 1R (one DIMM per channel, single-rank RAM). is capable of running up to 8400 MT/s. With both channels populated by 1 DIMM = bandwidth up to 134.4 GB/s.
2DPC, 1R/2R (two DIMMs per channel, single/dual rank RAM), is capable of running up to 6400 MT/s. With all 4 slots populated = bandwidth up to 102.4 GB/s.
There is no guarantee that you can get faster RAM or more DIMMs running other than specified. It is 50:50 chance.
So, all the DDR5 RAM kits/sets, that are 2x DIMMs with 6400+ MT/s speeds and aren't listed in MoBo memory QVL, are praying for lady luck, that you can actually get these kind of high speeds running.
CUDIMM helps to stabilize speeds of 6600 MT/s and up, but Ryzen 9000-series doesn't support CUDIMM fully. On AMD, CUDIMM RAM does work, but in bypass mode. Intel CPUs (Core Ultra 200) do support CUDIMM of the bat.
E.g here's one of the latest vids from JayzTwoCents, where he bought 2x 16GB, 8000 MT/s RAM to run on his AsRock X870E Taichi, paired with R9 9900X3D.
MoBo memory QVL didn't say a dime of supporting that fast of a RAM, but Jay got 7800 MT/s running, while 8000 MT/s failed to POST.
View: https://www.youtube.com/watch?v=GFU5CgtOs_U
For Jay, 7800 MT/s speeds gives him bandwidth of up to 124.8 GB/s.
So, if you want a guarantee, pick the RAM listed in your MoBo memory QVL. Else-ways, you'll be rolling the dice and praying for lady luck.
Or play it safe, go with 2x 6400MT/s, 2R RAM and be happy with bandwidth up to 102.4 GB/s. While crossing fingers that memory controller (or applications) can actually utilize 2R RAM.
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