So these cards have 3.5 GiB and 0.5 GiB of memory.
We went throught this about 10 years ago with Intel northbridge,
where a 32-bit Windows saw typically 3.25 GiB with 4 GiB installed.
If you had PAE linux, you got almost 4 GiB, but not continuous.
Didn't nvidia learn from history? Repeat!