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[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk BIOS and Capacity Factors | Overcoming BIOS Disk Size Barriers ]

Upgraded Controller Cards

Another solution to size barriers for a system that cannot have its BIOS upgraded is the purchase and installation of an upgraded hard disk controller card. Such a card completely replaces the on-board IDE/ATA controller hardware of your system, and in doing so, eliminates any BIOS size restrictions associated with the controller in your system.

These cards differ from BIOS expansion cards in that they are not just BIOS code, but rather a complete controller including the IDE/ATA ports. To use this hardware, you install the card and then move your hard disk cable(s) to attach to the new card instead of the ports on your motherboard. These controller cards are also generally more expensive than straight BIOS expansion cards, but we're still not talking about a lot of money here: generally less than $50.

The Promise Ultra66 PCI IDE/ATA controller
card, one of the most popular on the market.

Image Promise Technology, Inc.
Image used with permission.

Despite being more expensive and more complicated than BIOS expansion cards, these upgraded controller cards are more popular. There are a few issues involved in choosing them however:

  • System Bus Matching: You need to make sure you get a card that works with the system bus type that you are using. Today, PCI controller cards are pretty much the only ones available. If your system uses the VESA local bus (VLB) you may be able to find a controller that will work with that older bus, but to be honest, any system that old is probably getting to the point where spending money upgrading it may be a bad use of funds. If your system only supports ISA then you should really be looking at a new system! The ISA bus is so slow and such systems are so ancient that there's generally no point in even trying to upgrade them.
  • Controller Conflicts: If you use an add-in card to replace an older hard disk controller card (as is the case with most VLB systems) you just need to take the old card out and replace it with the new one, making sure it is configured properly. If you are putting the card into a PCI-based system that has the hard disk controller built into the motherboard, you should disable the controller in the BIOS setup program or the two controllers may conflict and your system will not work. (Some systems will stubbornly refuse to disable the controller; if your system is like this then this solution is not for you.) Many newer systems that support PnP will let an add-in controller work with its existing controller, but there are other issues. You will spend an IRQ on the new card, and you may not be able to control whether the drives on the new card are "seen" by the system before or after the ones on the existing controller.
  • Compatibility Issues: These are atypical but there have been occasional problems caused by replacing the existing controller with an add-in card. Mostly these add-in controllers work rather well, though.

Next: Software Translation Drivers (Dynamic Drive Overlays)

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