Regarding DDR5 Specs

[Shrek]

Of course, slower memory is NOT better; I did not mean to imply anything of the sort.

What I meant is that CAS latency only looks like it is getting worse with speed, since it is in clock cycles. So, it will only look like it is getting better if one runs the memory slower, which would be a crazy thing to do, although technically the number would get less.

Put another way, if the CAS number doubles with doubling speed, the CAS latency has stayed the same, not got worse. One could see that with the data I gave for my DDR3 RAM

Frequency	CAS# Latency
381.0 MHz	5
761.9 MHz	10

Running at 381.0 MHz would improve the CAS# but not the real CAS Latency (which is 13nS in both cases)

So, if I had RAM that could run at double 761.9 MHz, I should not view a CAS# of 20 as a drop in CAS performance.

 

[Wirko]

You need a CPU that supports both DDR3 and DDR4. Do any exist?

Skylake and Kaby Lake support DDR4 and DDR3L, the lower voltage version of DDR3. Using plain DDR3 means overvolting and Intel warns against that.

 

[damric]

You need a CPU that supports both DDR3 and DDR4. Do any exist?

Every Skylake iteration contains a standard DDR3 memory controller. There just aren't many boards that were DDR3. The DDR3L thing was debunked a long long time ago. I was one of the ones running DDR3-2400CL9 1.65v for years on Skylake before finally moving to Ryzen. What a lot of people don't know though is that even coffee lake and the other 14nm successors had capability of running DDR3, only limited by finding a board capable. There were even hackers running coffee lake, ect on Z170.

Then if you wanted to test DDR2 vs 3, Phenom II and Athlon II could run on both the AM3 as well as AM2/+.