Interesting bit about GDDR7
The biggest fundamental change with GDDR7 is that it will use PAM3 signaling, where GDDR6 uses NRZ (non return to zero) signaling — and GDDR6X uses PAM4 signaling. PAM3 (3-level pulse-amplitude modulation) reduces energy requirements compared to NRZ, while being less complex to implement than PAM4 (4-level PAM). That should make GDDR7 manufacturing equipment less complex and less expensive, though that doesn't mean it will be inexpensive.
GDDR7 will also support non-power-of-two configurations, and we expect to see 24Gb and, eventually, 48Gb memory chips. GDDR6 may also have 24Gb solutions coming, though no company has shipped a product using such a configuration at present.
This means 50% more memory can be put on each 32-bit interface so that a typical 128-bit graphics card, for example, could have 12GB of VRAM instead of only 8GB.
Another change is that a 32-bit GDDR7 memory interface gets subdivided into four 8-bit channels, which helps facilitate fetching larger chunks of data. Where GDDR5 was an 8n prefetch, and GDDR6 was 16n, GDDR7 will have a 32n prefetch architecture. This is a way to pull larger amounts of data from DRAM while still operating at relatively low clocks.
https://www.tomshardware.com/pc-components/gpus/what-is-gddr7-memory