[CentOS] mtrr error

Wed Oct 13 13:24:24 UTC 2010
Shouben Zhou <Shouben.Zhou-1 at nasa.gov>

I need your help and DEL's tech support doesn't provide any help on this 

We have  a lot of different type of DELL desktops from old-type 
hyper-thread cpu, to dual-core and quad-core cpus (most are Xeons). We 
run all versions of CentOS, but most are latest 5.5 (also up-to-date) 
and are very happy about that. The primary software on those Linux 
systems is IDL, which uses OpenGL libraries usually comes with video 

Now we are having problem with DELL T3500 with six-core cpu (6 GB 
memory). This is the only T3500 and six-core cpu we have right now.  
Here is the fact:

1. on T3500 with six-core, CentOS5.5, video card ATI Profire 2260, IDL 
7.1. Using dmesg, it report

mtrr: type mismatch for e0000000,10000000 old: uncachable new:
>>>>>>>>>> write-combining
>>>>>>>>>> mtrr: type mismatch for e0000000,10000000 old: uncachable new:
>>>>>>>>>> write-combining

when run IDL with simple draw function, got segmentation fault


reg00: base=0xdff00000 (3583MB), size=   1MB: uncachable, count=1
reg01: base=0xe0000000 (3584MB), size= 512MB: uncachable, count=1

Then I switched another ATI RV370, the mtrr error is gone, but still got segmentation fault


2. on T3400 with dual-core, CentOS5.5, same ATI RV370 video card and IDL 7.1, everything works just fine. By the way, we have never had any such problem with all our DELL boxes using CentOS and IDL

on T3400, the /proc/mtrr:

reg00: base=0x00000000 (   0MB), size=65536MB: write-back, count=1
reg01: base=0x3ff00000 (1023MB), size=   1MB: uncachable, count=1
reg02: base=0x40000000 (1024MB), size=1024MB: uncachable, count=1
reg03: base=0x80000000 (2048MB), size=2048MB: uncachable, count=1

When googling, someone out there suggest manually configure the MTRR, can somebody help us how to configure this six-core's MTRR? I am guessing this must be MTRR related. Is it possible the current Linux kernel doesn't understand six-core very well?


Shouben Zhou
Science Systems and Applications Inc.(SSAI)
1 Enterprise Pkwy, Hampton, VA 23666
Tel: (757)951-1905  Fax: (757)951-1900
Email: Shouben.Zhou at nasa.gov