在Intel 915G芯片组技术手册上,解释了“浪费”掉的750MB的地址空间是被芯片组的一些功能占用了,所以4GB实际上只有3.25G能用,具体如下:
*BIOS/firmware hub (2 MB)
*Local APIC (19 MB)
*Digital Media Interface (40 MB)
*Front side bus interrupts (17 MB)
*PCIe configuration space (256 MB)
*MCH base address registers, internal graphics ranges, PCIe ports (up to 512 MB) . This must be allocated in uninterrupted 256MB blocks.
*Memory-mapped I/O that is dynamically allocated for PCI Conventional and PCIe add-in cards (Typically this is around 200MB or more)