Or was I dreaming?
Yes you are dreaming. The 32bit system can only address 4GB (to be exact it is 4GB minus 1 byte) of address space and any device/function of the system that requires address space has to be mapped into these 4GB. Some of it is explained in this article
, but if in addition you have a graphics card with address space requirements, that goes against the 4GB too. In a bad case you can end up with only something between 2 and 3GBs that remain for the OS.