0 Replies Latest reply: Apr 21, 2011 9:37 AM by nando4 RSS

    Criteria for 36/64-bit 4500MHD PCI bar use in Win7?




      I've got an unusual situation where a Dell Inspiron 1440 with 4500MHD/GM45 + T6600-2.2 CPU can setup 36-bit PCI BARs for use in Win7 as described at




      We can see in the link the 4500MHD 256MB prefectable BAR is located at the 12.25GB (36-bit) boundary. THis is great as it allows the 32-bit freed space to be used for an external desktop GPU which doesn't support 36-bit PCI BARs.


      However, Dell Latitudes with P8xxx/T9xxx CPUs cannot do this, nor can a 2530P with a 4500MHD/GS45 + SL9400-1.86 CPU. In both cases Win7 moves the BARS back into 32-bit space, presumably because 36-bit is inaccessible. This is explained further at




      I'm wondering if it's the CPU that's preventing this from happening, or something else. PAE/DEP settings in the BCD don't fix the problem. If it's the CPU then,what MSR bit do I need to set to enable 36-bit PCI BAR usage in Win7? I hope the chipset isn't somehow limiting the PCI access to 32-bit only.


      : confused :


      Any help would be appreciated.