MFM vs IDE hard drives

IDE was the standard PC hard drive connection type for around a decade and a half. The only standard that outlasted it was SATA, which is a direct descendant. IDE was a much greater departure from the standard it replaced, which we commonly call MFM.

IDE was an acronym for Integrated Drive Electronics. The earlier standard, which we colloquially call MFM but would more properly call ST506, put most of the drive control logic on the host interface, which was whatever controller card you connected to the computer to interface it to the drive.

MFM vs IDE: A matter of technology catching up

Internally, MFM and IDE hard drives still work much the same way. But IDE drives are much more plentiful and reliable if you need a drive for a vintage computer today.

In the early 1980s, it just made sense to separate the controller from the drive the way MFM or ST-506 did. As large as drives were in the early 1980s, there wouldn’t have been room to integrate any more of the electronics into the drive itself.

As the end of the decade approached, advances in miniaturization made it practical to rethink this arrangement and place most of the electronics on the drive PCB itself. This made setup much easier, since the controller and the drive were meant to go together. You no longer had to tell the controller everything about the drive you connected to it. Not only that, you didn’t have to tell the computer all of those details either. The computer could query the drive to get the information needed. And if you had an older computer that didn’t have the capability to query the drive, you could just pick the closest match, and the drive was smart enough to translate.

Installing a hard drive went from something best left to a trained technician to a process that could easily be described in a short booklet. It was also a process the drive manufacturer could reasonably expect to be able to walk a consumer through over the phone.

Early misconceptions about IDE

That’s not to say there weren’t some early misconceptions. Early magazines described IDE drives as not needing an expensive controller card because the drive itself contained the controller electronics. But you did still need an IDE interface if your computer didn’t happen to already have one. It cost a lot less than traditional controllers. But the phrasing confused some people. Some consumers read those articles and concluded they could just buy that cheap IDE drive and not need anything else in order to use it. The interface card cost $15 or $20, but that wasn’t zero.

Working at retail selling computers in the early to mid ’90s, I learned the hard way to ask a customer who was purchasing a hard drive whether they were installing the drive in a computer that already had one or not. Some people bought the drives thinking they didn’t need anything additional to be able to use it.

That became less of a problem as IDE interfaces became integrated onto motherboards.

And to be fair, the transition didn’t confuse everyone. Yes, it confused and upset some people. But it solved bigger problems than it caused. In the end it was a net positive.

MFM vs IDE today

Today, there are some computers that only work with the MFM or ST-506 variety of drives. But when it comes to PCs, the only advantage of MFM over IDE is period correctness. Those early 5.25″ drives sound different from later IDE drives. But IDE drives are much more plentiful and reliable. When you have a choice, it’s cheaper and easier to get an IDE drive up and running in a vintage computer today.

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One thought on “MFM vs IDE hard drives

  • May 3, 2023 at 3:45 pm

    IDE also later became known as PATA, making the parallel (sic) with the related SATA standard more explicit. The PATA standard also included Ultra versions with higher data rates, stepping up from the original 33M transfers per second to 66M, 100M, and 133M and using DMA on the host computer end. The drives were backward compatible, so you could use the new drives in systems that only implemented the original 33M version.

    Even the fastest version of PATA was a bit slower than the original version of SATA, which did 150M transfers per second. That later increased to 300M and 600M, the final version of SATA. After that we got the shift to NVMe for faster speeds.

    PATA to SATA bridge boards are available, so it’s possible to put a SATA drive (including an SSD) into a computer that only has IDE/PATA ports. Compatibility with older systems can be problematic because they only understand small drives, and you can’t get SATA drives that are small enough!


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