i have 2 CRS328-24P-4S+ one says cpu count 1 and the other cpu count 2… what is the correct?
The SoC looks like it’s a dual core part. It looks like the first one is running ROS6 and second ROS7. I would assume the old kernel in 6 is just seeing 1 core (or has it disabled for stability reasons) and 7 fully supports the cpu and sees both the cores.
Exactly what @cdemers noted: ROS v6 only supports single core on these devices, v7 supports all present (2 in this device). Left screenshot shows ROS 6.49.5, right shows 7.2.1.
BTW, at the time of writing this post product page specifies single CPU core, so consider the second one enabled by v7 an Easter egg 
BTW2, it seems you upgraded the left unit to 7.2.1 and later downgraded it to 6.49.5 … do you mind sharing the reason for doing it?
Can confirm, the same happened when i upgraded a CRS326-24G-2S+, has two CPU’s enabled in ROS7
i downgraded because i had delays on ethernet traffic and a lot of packet loss when i did bandwidth test to my main router rbr4011
If you are using your CRS as a switch and you have it properly configured, then I think v7 brings very little compared to v6 feature set (perhaps a bit better SFP+ module support). So you’re probably better off staying with v6.49 … CPU core count should not affect device’s performance at all.