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VIAIDE(4)                    Device Drivers Manual                   VIAIDE(4)

NAME
     viaide - AMD, NVIDIA and VIA IDE disk controllers driver

SYNOPSIS
     viaide* at pci? dev ? function ? flags 0x0000
     options PCIIDE_AMD756_ENABLEDMA

DESCRIPTION
     The viaide driver supports the following IDE controllers and provides the
     interface with the hardware for the ata driver:
           -   Advanced Micro Devices AMD-756, 766, 768 and CS5536 IDE
               Controllers
           -   NVIDIA nForce, nForce2, nForce2 400, nForce3, nForce3 250,
               nForce4, MCP04, MCP55, MCP61, MCP65, MCP67 IDE and SATA
               Controllers.
           -   VIA Technologies VT82C586, VT82C586A, VT82C586B, VT82C596A,
               VT82C596B, VT82C686A, VT82C686B, VT8233, VT8233A, VT8233C,
               VT8235, VT8237/VT8237R/VT6420, VT8237A, VT8237S, VT8251,
               VT8261, CX700(M/M2), VX700, VX800/820, VX855/875, VX900/VX11
               Integrated IDE and SATA Controllers, VT6415/VT6330 single-
               channel IDE Controllers, VT6410 IDE RAID Controller, and VT6421
               SATA RAID & IDE Controller.

     The 0x0002 flag forces the viaide driver to disable DMA on chipsets for
     which DMA would normally be enabled.  This can be used as a debugging
     aid, or to work around problems where the IDE controller is wired up to
     the system incorrectly.

SEE ALSO
     ata(4), atapi(4), intro(4), pci(4), pciide(4), wd(4), wdc(4)

BUGS
     The AMD756 chip revision D2 has a bug affecting DMA (but not Ultra-DMA)
     modes.  The workaround documented by AMD is to not use DMA on any drive
     which does not support Ultra-DMA modes.  This does not appear to be
     necessary on all drives, the PCIIDE_AMD756_ENABLEDMA option can be used
     to force multiword DMA on the buggy revisions.  Multiword DMA can
     eventually be disabled on a per-drive basis with config flags, see wd(4).
     The bug, if triggered, will cause a total system hang.

     The timings used for the PIO and DMA modes for controllers listed above
     are for a PCI bus running at 30 or 33 MHz.  This driver may not work
     properly on overclocked systems.

NetBSD 11.99                   October 17, 2025                   NetBSD 11.99