DDR6 looks set to double data speeds over DDR5, with DDR6-21000 being the ultimate target

pcgamer.com:

Every processor is limited in some way by the speed of memory, and DRAM manufacturers are pushing ahead with the development of DDR6, the next generation of RAM after DDR5. Details from Synopsys show that the technology is on target to finalise next year, with data speeds of up to 17,600 MT/s and the potential to reach 21,000 MT/s or DDR6-21000.

News of the progress, plus information about the fundamental changes in DDR6 compared to DDR5, were given via a presentation by Synopsys, who manufacture RAM controllers and interfaces. That was shared/leaked by Twitter user Darkmont, but it's also backed up by a JEDEC presentation on LPDDR6 (via Videocardz), with both documents going into a lot of detail about the forthcoming RAM technology.

At the moment, DDR5 tops out at around 8,400 MT/s (aka DDR5-8400), though LPDDR5x is a smidgen faster at 8,533. While we'll probably see some hugely expensive DDR5 kits that run quicker than this at some point in the future, we're unlikely to break the 10,000 MT/s barrier at an affordable price with DDR5.

According to JEDEC and Synopsys, DDR6 is on track to launch at 8.8 Gbps and eventually reach 17,600 MT/s, with a dizzying 21,000 MT/s being potentially achievable. At the moment, JEDEC and its associates are undecided as to what signalling mode to use (PAM or NRZ), hence why the target date for launch isn't until the second half of 2025. LPDDR6 isn't expected to be quite as fast, but a peak of 14.4 Gbps isn't to be sniffed at.

Internally, DDR6 memory chips will be quite different to DDR5 ones, in that rather than using dual 16-bit data channels per module, the new design will use dual 12-bit channels instead. The faster data transfer rate offsets the narrow data channels, so a single DDR6-17600 module has an effective bandwidth of just under 47 GB/s.

If that doesn't seem quite right, it's because a DDR6 module transmits 288 bits per cycle, but only 256 bits of that is actual data. So the formula for calculating the effective bandwidth