| GEODEIDE(4) | Device Drivers Manual | GEODEIDE(4) | 
geodeide —
geodeide* at pci? dev ? function ? flags 0x0000
geodeide driver supports the AMD Geode CS5530A and
  SC1100 IDE controllers, and provides the interface with the hardware for the
  ata(4) driver.
The 0x0002 flag forces the geodeide 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.
The CS5530 multifunction chip/core's IDE section claims to be
    capable of UDMA mode 2 (33.3MB/s) but in practice using that mode swamps the
    controller so badly that geodeide limits the UDMA
    negotiation to mode 1 (25MB/s) so that the other functions of this chip
    continue to work.
The IDE DMA engine in the CS5530 can only do transfers on cache-line (16-byte) boundaries. Attempts to perform DMA on any other alignment will crash the system. This problem may also exist in the SC1100 since the CS5530 was its direct predecessor, and it is not clear that National Semiconductor fixed any bugs in it.
The geodeide driver will reject attempts
    to DMA to buffers not aligned to the required boundary. The
    wd(4) disk driver will back off to
    PIO mode to accomplish these transfer requests, at reduced system
    performance.
| July 5, 2005 | NetBSD 10.1 |