⚛ (0xe2.0x9a.0x9b.delete@this.gmail.com) on October 28, 2020 4:04 pm wrote:
>
> DDR5: The dimensions of DDR5 memory modules are the same as DDR4, so although DDR5 will improve
> iGPU performance (by my estimates: by about 40% when upgrading from DDR4-3200 to DDR5-4800)
> the number of DDR5 memory modules in a PC will be the same as with DDR4. It is probable that
> dual-channel DDR5 will remain to be the maximum number of memory channels in all desktop PCs
> and notebooks with APUs. On the other hand, socket LGA 1700 has more pins than LGA 1200.
>
> -atom

Memory chips intended for GPU applications, including GDDR5, are available in much wider but shallower configurations so the same amount of memory can have a much higher bandwidth with as few chips as possible. System memory of a similar width would only be appropriate for massive amounts of memory.

So for instance GDDR5 chips are 32-bits wide and it takes 8 chips to make a 256-bit interface width. The same width using commodity 8-bit wide DDR4 would require 32 chips and with the same density, have 4 times the amount of memory which would be completely uneconomical except for compute applications where this has been done in the past.