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[ The PC Guide | Systems and Components Reference Guide | Motherboard and System Devices | System BIOS | BIOS Settings | IDE Device Setup / Autodetection ]


This setting determines the "type" of the IDE device. In the early years of the PC, there were few different types of hard disks, and there were far less sophisticated BIOS setup programs. There was no autodetection for hard disks, and no way to manually enter the parameters for the hard disk. You selected the "type" (really a number, usually from 1 to about 45 or so) of the hard drive from a predefined table that was hard-coded into the BIOS. Different machines would have different tables, and newer machines would have more newer drives in their tables than older machines did. If you tried to put a new drive in an older machine you might find it had no entry that matched, and you'd have to use the "best fit" entry you could find, sometimes losing some of your drive's capacity. Overall, it was a big pain. :^)

Newer BIOSes don't restrict you to using the entries in the fixed "disk type" table, although the table of fixed entries still persists. In today's BIOSes, you will normally have the following options for each device's "Type":

  • Predefined Types (1-45, 1-46, or 1-47): This is the predefined fixed table mentioned above. Even on new machines this table generally contains entries for teeny-tiny, very old drives (like 40-100 MB). It is strongly recommended that you avoid the use of this table altogether.
  • User: This option lets you manually specify the parameters for the drive. Not recommended unless you really know what you are doing (actually, not recommended even then unless there is a specific reason you need to do this.) "User" is normally what the BIOS will set the drive to when you do a manual autodetect.

Note: Instead of "User", some systems use the last number in the table for user settings. If entries 1-46 for example are predefined drives, the BIOS may call the "User" setting "Type 47". It's still the same thing, just with a different name.

  • Auto: This setting activates dynamic IDE autodetection for the device. The device will be autodetected by the BIOS each time the system boots.
  • CD-ROM: Some systems now support this entry, to tell the BIOS that you are using a CD-ROM in that IDE device position.
  • Disabled / None: Use this option to tell the BIOS that there is no drive at all in this IDE device position.

Some BIOSes implement manual autodetection of IDE devices using the "Type" setting. By pressing {Enter}, the BIOS will autodetect the device, set the type to "User", and set the other numbers and options for you. Most BIOSes however have a dedicated menu entry for autodetecting all IDE devices.

If you select anything for "Type" other than "User", the BIOS will lock the "Size", "Cylinders", "Heads", "Sectors", "Write Precompensation" and "Landing Zone" settings, since these will be determined either by reading the fixed table, or by dynamic autodetection (if you select "Auto"). CD-ROMs do not use these physical geometry parameters since their construction is totally different.

If your system supports the "Auto" setting, you are generally best off using it. This will ensure that your system is always set up correctly. You should set to "Disabled" any devices you are not using, and use "CD-ROM" for IDE CD-ROM drives.

Note: Some BIOSes do not have a "Type" entry for CD-ROMs, but will autodetect a CD-ROM at boot time. In this case, it is best to set that device to "Auto".

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