Celistica with AMD chip-set

["Richard B. Johnson" <root@chaos.analogic.com>]

Hello all,

The Celistica server with the AMD chip-set has very poor
PCI performance with Linux (and probably W$ too).

The problem was traced to incorrect bridge configuration
in the HyperTransport(tm) chips that connect up pairs
of slots.

I don't know how to make a generic chip-set bug-fix, and
probably a new BIOS will come out with the correct values
in the registers. But right now, the following initialization
code will fix the box.



//-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//
//  Some kind of problem, here. If the HyperTransport(tm) bridge
//  is found, one of the register values needs to be changed to
//  fix the bus performance. Need to turn back on prefetch.
//

    while((pdev = pci_find_device(0x1022, 0x7450, pdev)) != NULL)
        pci_write_config_dword(pdev,  0x4c, 0x2ec1);



Cheers,
Dick Johnson
Penguin : Linux version 2.4.26 on an i686 machine (5570.56 BogoMips).
          "DMA used to run at 180 Mb/s. With the new hardware it's only
           30 Mb/s. Must be a software problem......." -actual complaint.
            Note 96.31% of all statistics are fiction.