Local (CPU) APIC address?

[Robert_S_1]

Hello,

I was reading the "Desktop 4th Generation Intel® Core™Processor Family" Datasheet at https://www-ssl.intel.com/content/dam/www/public/us/en/documents/datasheets/4th-gen-core-family-desktop-vol-2-datasheet.pdf

...and it shows the Local (CPU) APIC address to be at FEC80000h -

But then underneath it says the following -

"Memory requests to this range would then be forwarded to the PCI Express* port. This mode is intended for the entry Workstation/Server SKU of the PCH, and would be disabled in typical Desktop systems. When disabled, any access within the entire APIC Configuration space (FEC0_0000h to FECF_FFFFh) is forwarded to DMI."

This contradicts what the image shows and suggested that FEC0_0000h to FECF_FFFFh will go to the DMI to the I/O Apic.

I have checked the MADT tables and it shows the local CPU address to be FEE0_0000, which it is on most systems. This then clashes with what is shown to be MSI interrupts.

2 questions then really,

Do both the local CPU APIC and MSI interrupts use FEE0_0000h?

What is this range between FEC8_0000h - FECF_FFFF for?

My CPU is the Core i5 4570 on the Z87 chipset.

Any help would be appreciated.

Kind Regards,

Robert Smith

[Robert_S_1]

Any help clearing this up would be appreciated.

Thanks.

[Harold_G_Intel]

Hi Robert,

You might try the processor community if you have not already done so.

https://communities.intel.com/community/tech/processors

You can also send an email directly to processor support from here: 

http://supportmail.intel.com/scripts-emf/welcome.aspx?id=37

Regards, Hal G

Intel(R) Developer Zone Support

http://software.intel.com
*Other names and brands may be claimed as the property of others.

[Robert_S_1]

Thanks Hal,

I've sent an E-mail to Processor support.

Kind Regards,

Robert

[Bernard]

Are you using Linux or Windows?

[Robert_S_1]

Hi liyapolak,

I am on Windows 7

Thanks.

[Bernard]

>>>What is this range between FEC8_0000h - FECF_FFFF for?>>>

Did you try to check with the windbg  quoted address range?

[Robert_S_1]

Hello,

I think I've figured it out.

The Haswell datasheet says "The processor optionally supports additional I/O APICs behind the PCI Express* “Graphics” port. When enabled using the APIC_BASE and APIC_LIMIT registers (mapped PCI Express* Configuration space offset 240h and 244h), the PCI Express*
port(s) will positively decode a subset of the APIC configuration space."

Looking back at older datasheets the area between FEC8_0000 and FECF_FFFF is called the 'PCI Express IO APIC space'.

As the PCI Express ports are in the physical CPU in newer CPUs it is listed as a 'local (CPU) APIC' address range and is nothing to do with the local APIC and MSI range at FEE0_0000.

Thanks for the help,

Robert

[Bernard]

You are welcome.