What is the minimum graphics memory (VRAM) for Unity Desktop? (Ubuntu 16.04)

(Info: I searched this on Google several times and I could not find anything, so if this is a duplicate, let me know. Also, let me know if I'm unclear or too broad.)

I am getting a new motherboard on Saturday and my friend (who is building it) said that he is also bringing a graphics card (an AGP one with 512 MB video memory).

When he mentioned it, I was happy to know that now I can "break free" from the lightweight Ubuntu options (Xubuntu, Lubuntu) and use Unity desktop once again.

But, I had some doubts. Will 512 MB be enough for Unity on 16.04? I think that 64 ~ 70 MB is the bare minimum (tested with 96 MB on a 14.04 VM & with 128 MB on a 16.04 VM). Also, will AGP be fast enough to render the graphics? There is a lot of debate going online on whether they are faster than PCI or not.

I'm open to any suggestions.

EDIT: This is the graphics card I'm getting:

Radeon X1650Pri Dual Link DVI 512MB DDR2 (128-bit)

Is it OK?

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