How to Use Hard Drives Larger than 540Mb on 386 Motherboards

Each storage location on a hard drive has a physical address that must be translated.

The original ATA standard for IDE hard drives was limited to no more than 528 MB capacity and supported PIO modes 0, 1 and 2. This limitation was due to the number of bits used by the processor, BIOS and operating system to address locations on the drive, and various other limitations were presented over time as this one was overcome. In order to use a drive larger than 540 MB on computers that do not support the capacity on a hardware or BIOS level, expansion boards or drive overlay software must be installed to translate the physical drive addresses.

Things You'll Need

• Hard drive overlay software
• Hard drive controller board
• Anti-static wrist strap
• Screwdriver set
• Flashlight

Instructions

Drive Overlay Software

1. Install the hard drive according to the drive or computer manufacturer's instructions from the specific model being installed. Set the Master / Slave / Cable Select jumper according to the system specifications, typically setting the primary drive to "Master" and the secondary drive to "Slave" when they are located on the same cable, but setting both drives to "Cable Select" on some systems.

2. Insert the drive overlay software boot disk into the floppy drive or the optical drive as appropriate, then power on the computer. Boot from the drive overlay disk if prompted.

3. Select the option to install drive overlay software onto the new drive and to create a partition, and format it for the full capacity from the boot menu.

4. Remove the drive overlay software disk when the installation has completed and restart the computer. It may be necessary to reinstall the operating system if the new drive is the primary drive in the system. If this is the case, insert the first operating system disk into the appropriate drive and restart the computer. Follow the prompts to reload the operating system.

Hard Drive Controller Card

1. Power down the computer and detach the power cord from the back of the unit.

2. Connect the anti-static wrist strap to one of the fan exhaust holes and attach the other end to one wrist.

3. Remove the cover of the computer and locate an available expansion slot that matches the hard drive controller interface.

4. Remove the blank slot cover by removing the single screw that holds it in place.

5. Insert the hard drive controller card into the open slot by pushing it straight down until it is firmly seated, then attaching it to the case with a single screw.

6. Connect the hard drive data cable to the controller card, being sure to connect Pin 1 on the cable (marked by a colored stripe on one edge of the cable) to Pin 1 on the card (marked on the card).

7. Install the hard drive according to the instructions from the drive or computer manufacturer for the specific model being installed. Set the Master / Slave / Cable Select jumper according to the system specifications, typically setting the primary drive to "Master" and the secondary drive to "Slave" when they are located on the same cable, but setting both drives to Cable Select on some systems.

Tips & Warnings

• Back up any data on the target computer or on the additional drive prior to installing drive overlay software, as it typically formats and erases the contents of the drive. Consider upgrading the motherboard and CPU instead of adding a controller card to older systems for additional capability.

• Internal components, controller cards and hard drives are static sensitive, and an anti-static wrist strap should always be used when working inside a computer. Do not subject the hard drives to vibration or impact, or move a drive when it is on. Hard drives should be securely mounted.

References

• Seagate: Medalist Pro Hard Drive Installation Guide
• Epson: Peer-2030 20 MHz 386SX System User's Manual
• Dewassoc: Hard Drive Size Limitations and Barriers

Resources

• Seagate: DiscWizard
• Online Computer Tips: Master, Slave, and Cable Select Hard Drive Jumper Settings