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Installing an IDE Hard Drive

Created on April 26, 2023

  1. Which Capacity?
  2. Connecting IDE Devices
  3. Configuring IDE Devices
    1. What about CD-ROM drives?
    2. Enabling UltraDMA
  4. CF Cards and Other Solid State Media

A lot of the time, a computer is expected to have some form of large storage in itself, where all the software can be executed locally. This isn't always the case when it comes to certain niche applications, but otherwise, the hard drive is one of the most important components of a computer.

There happens to be plenty of options regarding which hard drive you could pick for your computer, so which one should you go with? The short answer is to stick to a fast, spacious IDE hard drive, preferably 120GB or under (going for less than 32GB or 8GB may make your life easier depending on how old your computer is). IDE hard drives are simple to install, but depending on your application, it may be worth considering other options, including a hard drive using SCSI.

Guide: Connecting Internal SCSI Hard Drives
April 27, 2023 - Talking about SCSI is practically another subject in its own right, as it's WAY more complicated to set up. Even so, it could be worth your time. Some things you'll be in for here include the ability...

IDE hard drives are very common, and are suited very well to computers with a single hard disk. They're also easy to connect to most computers, and the majority of motherboards designed between 1995 and 2009 include onboard IDE connectors, so if you're just getting started with old computers and need to get a hard drive, get one that uses IDE.

Which Capacity?

The capacity of the hard drive you get may matter more than on simply how much data you intend to store on your computer.

The BIOS in some motherboards may have limits on how much space they can address on any single hard drive. There are a few ways to overcome the limitation; you could use a separate IDE controller with its own BIOS, or you could install some special software that may be capable of working around the capacity limit of the BIOS. It's also possible that your motherboard's BIOS may have an update available which can increase the limit of the disk capacity it can address.

The earliest computers are probably limited to addressing up to 512MB of space, which could be as late as some 486 motherboards designed in 1993 or 1994. Later motherboards should be able to go up to 8.4GB, or more ideally 32GB. For motherboards released in 2000 or later, you should expect the BIOS to be able to address hard drives up to 128GB in capacity, and finally, much later ones from, say, 2003 and onward should be able to address as much as 2TB, if not more. I don't think IDE hard drives beyond 1TB really even existed.

If possible, try to get an 8GB or 20GB hard drive or somewhere close to that; these capacities should be reasonable for a lot of installations.

Connecting IDE Devices

IDE cable with two drive connectors

Connecting IDE devices is straightforward enough. All you need is a simple, readily available cable. One connector on the far end will connect to your motherboard or controller card, and the other side will often have two connectors for your devices. The one on the edge connects to the master devices, and the middle connector connects to the slave device.

IDE cables with keyed connectors

IDE cables and connectors have evolved throughout their lifespan to be easier to connect. Some connectors, such as the one depicted on the left, intentionally have one pin blocked out, specifically pin 20. This pin serves no function, so removing it on both the controller's connector and the cable will ensure the cable can only be plugged in one way.

Other cables, such as the one on the right, have notches on one side of the plastic shell for each connector. They work when an IDE controller's connectors also have outer frames with notches, so when plugging notched IDE cables into them, they can only be inserted in one direction. Many IDE cables have both types of keyed connectors.

Keyed connectors started becoming a lot more prevalent sometime around 1996, but some older connectors do not take such features into account, perhaps to maintain mechanical compatibility with much older drives which were not designed with the conveniences in mind.

IDE cables connected adjacent to pin 1 on the controller

In situations where your IDE cable has no keying, one side of the cable should have a distinct color from the other pins, which could be solid or dotted. This indicates that side of the connector has the first pin. This pin needs to be adjacent, or right next to the first pin of the connector on the IDE controller. The controller should have a label indicating where pin 1 is.

IDE connector without keyed pinout

If the connectors on your IDE controller do not have pin 20 removed for keying, you may prefer to use an unkeyed cable with it if you have one. Otherwise, you will have to remove this pin yourself by wiggling it off with some sort of small, narrow, handheld pliers. This should not impact the operability of the IDE channel in any way, but you need to be careful and make sure you are removing the correct pin!

A cheap way to know the right pin to take out is to take a keyed IDE cable and place it over an unkeyed connector on the controller, making sure they are aligned exactly as they would be. The pin in the middle that's blocking the connection is the one to remove.

Seagate Medalist hard drive

Due to the way IDE works, it's often advised that you connect your hard drive to the master port to maximize its performance. Other devices such as CD-ROM drives should be configured with the slave setting if no other IDE channels on a system are available.

Connectors on back of IDE hard drive

Furthermore, all IDE hard drives must have a jumper set to either master or slave depending on how the drive is being connected. A jumper is a small plastic block with gold contacts inside that shorts a couple of pins to assign a setting for a hard drive or any other device.

IDE connectors on a motherboard

Each IDE connector on a motherboard or controller card is one channel. While most ISA-based I/O controllers intended for 386 and 486 computers have just one IDE channel, the majority of motherboards from the time of IDE's relevance will have two. Onboard dual channel IDE is plenty enough for the majority of consumers. For systems with just one hard drive and one CD-ROM drive, both channels can be used, and both devices can be configured as master, since no other devices occupy each channel.

Here is a picture of how two devices would be connected to one IDE channel, with the hard drive set as master and the CD-ROM drive set as slave:

Two IDE devices connected to one channel

To connect two devices to different channels, you set them both to master and use two IDE cables, connecting each device to the furthest end of a cable. Ideally, the hard drive is connected to the primary channel, and the CD-ROM drive is connected to the secondary channel.

Two IDE devices connected to two different channels

Of course, IDE cables are only for transmitting data. Power must be supplied by a Molex connector coming from your power supply. Modern power supplies do not have very many Molex connectors, so if need be, you can acquire SATA to Molex power adapters and connect your devices to them.

IDE 40-pin vs. 80-pin connector

One other thing worth noting about IDE is that if you're using an IDE controller with a bus speed of 66MB/s or faster (this started becoming more readily available in computers from 1999 and onward), it needs a better cable to achieve that speed.

The left cable is a traditional 40-pin cable. This cable is most appropriate for controllers that go up to 33MB/s, including the onboard controller found in motherboards using the Intel 440BX chipset and earlier. In faster controllers, 40-pin cables can still be used for slower devices such as CD-ROM drives, so as long as they reside on their own IDE channel.

The right cable has 80 pins, but the connector is exactly the same as that of a 40-pin cable. The way to distinguish an 80-pin IDE cable from a 40-pin one is by taking note to that the 80-pin cable has thinner grooves for each wire, and that there are more wires to begin with.

Both types of cables are interchangeable, but if a 40-pin cable is connected to an IDE controller running at 66MB/s or faster, it will not be able to operate at its full speed. On the flipside, there is no real benefit to connecting an 80-pin cable to an IDE controller running at 33MB/s or slower.

Configuring IDE Devices

Primary Master Hard Disk set to Auto in AMI WinBIOS

Thankfully, configuring IDE drive parameters in most computers is easy, as most BIOS setup utilities will often assign them for you based on the drive's specifications. This can be done either on the fly by setting each drive to "Auto" in the standard setup menu, or a utility in the BIOS can be used to automatically detect drive parameters and firmly assign them as if the user had entered them manually.

AMIBIOS Standard Setup with one hard disk configured

Automatically detecting the drive parameters from the setup utility as opposed to on every boot is useful for saving a little bit of time on every boot, but if you change your hard drive, you will need to remember to update the parameters to match the new drive. In some forms of AMIBIOS, you can go to the standard setup menu, highlight the drive you want to reconfigure, and press the enter key to automatically set the new parameters.

AwardBIOS IDE HDD Auto Detection

Many motherboards that use AwardBIOS may have a separate option in the setup menu specifically for detecting IDE hard drives. By running this, you'll be walked through every IDE device the system attempts to detect in its onboard controller. This is often labeled as IDE HDD AUTO DETECTION.

For older hard disks, detecting them from Setup rather than on every boot may be a necessity; I've found that using an old Conner hard drive on a Socket 7 system from 1998 can cause some things to lock up when using the latter approach.

It is possible that some early IDE hard drives may have no ability to be automatically detected, or the BIOS setup utility may have no auto detection functionality. In such cases, you will need to manually enter the drive parameters. These parameters should be found on the hard drive's label; write them down on a piece of paper so you know what they are before you install the drive in the computer.

Promise Ultra33 IDE controller

Some IDE controllers, like the PCI-based Promise Ultra33 and its successors, have their own separate BIOS which may always automatically detect IDE hard drives. This lineup of controllers in particular is very good for users who want superior disk performance on older motherboards, as well as the ability to bypass disk capacity limitations in the motherboard's BIOS, up to 128GB and possibly higher.

What about CD-ROM drives?

Ideally, you shouldn't have to worry too much about CD-ROM drive configuration; these should not require any parameters. The differences between the various BIOS incarnations can get a little bit weird, though. For instance, AMIBIOS has an option for assigning IDE drives as CD-ROM drives in the standard menu, whereas a popular incarnation of AwardBIOS may not.

You can, of course, set all or some of your drives to "Auto" mode, which should almost certainly relieve you from some degree of ambiguity, but one thing about AwardBIOS is that even if you set drives to "None", it may still try to detect ATAPI CD-ROM drives at those locations! This doesn't seem to be the case for AMIBIOS.

Add-on IDE controllers like the Promise Ultra series may not support CD-ROM drives.

Enabling UltraDMA

Usually, by default, hard disks rely on PIO for data transfers with IDE. This is the default setting in Windows 9x, and is the only available method on 486 computers and some early Pentium systems. In 1996 and onward, however, some chipsets like the Intel 430HX and 430VX introduced support for UltraDMA, which can be used instead of PIO to drastically improve disk performance on the onboard IDE controller while reducing strain on the CPU, freeing it to squeeze in other tasks during those long copy operations.

Windows 2000 and onward enables DMA for hard disks by default if it is available. Even if onboard IDE supports UltraDMA, it is possible that the BIOS may have it disabled; check in the setup utility to make sure it is intact.

DMA enabled on a hard disk in Windows 95

To enable DMA on a hard disk in Windows 95 OSR2, 98, or ME, go into the System control panel (which can be accessed by right clicking My Computer and selecting Properties), select the Device Manager tab, and select your generic IDE disk in the Disk Drives category. Double click it, and in the Settings tab there, check to see if there is an option for DMA. If there is, tick the check box to enable it. If the option is not available, it's possible that either your chipset or driver always has UltraDMA enabled for your disk, or it does not support the feature at all.

Windows 95A (or the original gold release) does not support UltraDMA, at least natively. Some drivers, like an old Intel BusMaster driver or the driver for the Promise Ultra series of IDE controllers, may utilize UltraDMA on their own (as the latter's product name ought to imply).

To enable UltraDMA in Windows NT or some other old operating system, you may need to load a driver of some sort. Newer operating systems, such as recent enough version of Linux or *BSD should use UltraDMA automatically. It may even be possible to use it in MS-DOS with the help of some other driver, but I have not tried this.

CF Cards and Other Solid State Media

If you do not want to deal with mechanical hard drives, there are other options available these days. In the past, I've used CF cards connected to IDE adapters in place of hard drives on some older systems, and I still use them in specific cases where I may want a small boot drive and a much larger drive for data, as well as for the rare occasion that I may send a computer to someone else in the mail.

CF card plugged into a slot mounted in an expansion bracket

Some conveniences of CF cards include it being easier to find them in smaller capacities, and that they can be mounted to an expansion bracket to make them easily removable from the back of the computer without having to open it. This makes it really easy to switch between operating systems without interference or load up an installation with necessary files using a newer computer with a simple USB media card reader. Other adapters also exist for SD cards.

Due to operating systems assigning swap memory space which is written to on a regular basis, CF cards could wear out faster than you may expect. Therefore, you should go for "industrial" CF cards whenever possible, as those may be designed to sustain far more write operations.

If you need to go for larger capacities, CF cards may not be a good option. You may instead wish to settle for a real IDE SSD, or something to that degree. It should be possible to find these in 128GB capacities, evenly topping off many BIOS limits. I have not tried these myself, though.

Whichever way you decide to go, installing IDE devices shouldn't be too difficult once you can get around any of its lesser known quirks.


Bird - April 28, 2023 at 01:00 AM

I wonder if IDE drives will run forever. Lots of them are in use since more than 20 years now and show no problems whatsoever. They must be extremly reliable.

XTac - April 26, 2023 at 02:48 PM

Personally, I would stick to CF card adapters for systems that have otherwise no easy way to transfer large files (486 and before). I had bad luck with them, and they are not cost efficient.

IDE drives or SATA drives with IDE adapters are definitely the most reliable option in my opinion.

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