Thank you that clarifies it.
On the logic board:
Hynix H5GQ1H24BFR 1 Gb GDDR5 SDRAM (Total of 4 Gb = 512 MB)
4Gb = 512 Mb??. Isn't 4Gb, you know = to 4Gb? Or does Gb mean something different in this context. There must be something here I'm not following