Ddr3 cpu using ddr5?

no, gpu and cpu are separate.

Graphics memory is rated differntly then processor memory ddr3 memory can reach the same frequency and higher then graphics ddr5 most ddr5 graphics memory is like 1800-2000mhz for nvidia and the new 7950 and 7970 from amd are at 1500mhz which is classified as ddr5 even though ddr3 can go to 2133 and higher for processor memory.

The CPU uses the DDR3 memory and is ignorant of the memory on the GPU, the GDDR5 memory on the GPU is only used by the GPU and does not require any compatibility with the motherboard or CPU as they have no idea what memory is on the GPU and don't care so it will work fine.