It's unlikely to be the chipset's fault unless it's a very old laptop - it's the BIOS' job to trigger the "hoisting" of physical memory that overlaps the PCI ad

It's unlikely to be the chipset's fault unless it's a very old laptop - it's the BIOS' job to trigger the "hoisting" of physical memory that overlaps the PCI address space so it lies above 0xFFFFFFFF once ACPI etc. have been initialised. Laptop/motherboard makers pay notoriously little attention to the BIOS, so features like this often stay disabled. Have you checked for a BIOS update? Interestingly, this also means that any memory that already lies beyond the 4GB barrier will be visible to the OS (64-bit or PAE) even without hoisting (so you'd see 7.3GB of 8GB) - unfortunately, upgrading to >4GB is expensive in Laptops at the moment. (4GB modules cost over 4x as much as 2GB DIMMs)