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Micron Accidentally Confirms GDDR6X Memory, and Nvidia's RTX 3090 GPU

Accepted submission by takyon at 2020-08-16 16:47:00

Micron Spills on GDDR6X: PAM4 Signaling For Higher Rates, Coming to NVIDIA's RTX 3090 []

It would seem that Micron this morning has accidentally spilled the beans on the future of graphics card memory technologies – and outed one of NVIDIA's next-generation RTX video cards in the process. In a technical brief that was posted to their website, dubbed "The Demand for Ultra-Bandwidth Solutions", Micron detailed their portfolio of high-bandwidth memory technologies and the market needs for them. Included in this brief was information on the previously-unannounced GDDR6X memory technology, as well as some information on what seems to be the first card to use it, NVIDIA's GeForce RTX 3090.

[...] At any rate, as this is a market overview rather than a technical deep dive, the details on GDDR6X are slim. The document links to another, still-unpublished document, "Doubling I/O Performance with PAM4: Micron Innovates GDDR6X to Accelerate Graphics Memory", that would presumably contain further details on GDDR6X. None the less, even this high-level overview gives us a basic idea of what Micron has in store for later this year.

The key innovation for GDDR6X appears to be that Micron is moving from using POD135 coding on the memory bus – a binary (two state) coding format – to four state coding in the form of Pulse-Amplitude Modulation 4 (PAM4). In short, Micron would be doubling the number of signal states in the GDDR6X memory bus, allowing it to transmit twice as much data per clock.

[...] According to Micron's brief, they're expecting to get GDDR6X to 21Gbps/pin, at least to start with. This is a far cry from doubling GDDR6's existing 16Gbps/pin rate, but it's also a data rate that would be grounded in the limitations of PAM4 and DRAM. PAM4 itself is easier to achieve than binary coding at the same total data rate, but having to accurately determine four states instead of two is conversely a harder task. So a smaller jump isn't too surprising.

The leaked Ampere-based RTX 3090 seems to be Nvidia's attempt to compete with AMD's upcoming RDNA2 ("Big Navi") GPUs without lowering the price of the usual high-end "Titan" GPU (Titan RTX launched at $2,499 []). Here are some of the latest leaks for the RTX 30 "Ampere" GPU lineup [].

Also at Guru3D [] and Wccftech [].

Previously: GDDR5X Standard Finalized by JEDEC []
SK Hynix to Begin Shipping GDDR6 Memory in Early 2018 []
Samsung Announces Mass Production of GDDR6 SDRAM []

Related: PCIe 6.0 Announced for 2021: Doubles Bandwidth Yet Again [] (uses PAM4)

Original Submission