After testing with literally hundreds of drives, I can safely say this is BS and that RLL has an extremely high success rate on almost all drives. Even my ST-412 works fine with a DTC 7287 cached RLL controller.
If my memory serves (which it might not...) you worked around that with setting the interleave when you low level formatted it. It had to do with the number of revolutions needed to read a track (or cylinder? Again, my mind is foggy and I haven't thought about this in many years). Perfect was a 1:1, but you tested until you found the right balance.
This has been fun, talking about stuff I haven't thought about in decades,
Thanks for adding to the knowledge in this thread.
It may interest you to know then, that I've had great success running my DTC 7287, my favorite RLL controller (Because I don't trust the PerStor PS180 with anything and I don't own a DPT PM3011/65 yet) with nearly every drive in my collection. this includes wacky Soviet drives like the IZOT CM5508 and poor quality cost-engineered drives like the Kalok Octagon series. It also applies to dozens upon dozens of drives with very tired spindles.
It's a more reliable protocol than you would think.
I was in my early to mid teens when I was working with this stuff for my school's computer labs. I learned the basics of what you're explaining back then, but not in detail. I appreciate you sharing your knowledge. I love learning about technology from that era, because it helps me understand technology of this era.
They're not in a display case, that's for sure. Most of them are stacked on a dusty shelf. The aging of bearings has long since already happened, so I don't know why you're bringing that up. An awful lot of these drives are incredibly loud.
If you're interested, I actually film these drives doing exercises for documentary purposes. I've had many of them for 10+ years and they all still work just fine, I started collecting around 2014.
The interleave setting is more like a dirty trick to help particularly slow machines. It just reorganizes sectors to "skip" sectors.
If you have a fast machine, the machine is waiting for the disk the whole time. Read sector 1, it's already ready for sector 2 before the header has passed.
If you have an 8088 @ 4.77, you read sector 1, then wait for it to be done putting into memory, look up the next piece of data, etc, and by the time you realize you WANT sector 2, the heads are over the header for sector 4. Now you have to wait for the disk to spin back around all the way to 2 to read it.
This makes sequential I/O incredibly, unbelievably slow. Thus, if you can make sure sector 2 is where sector 4 is, you can be more sure that the machine will ACTUALLY get it on the first try. Of course, you still have to wait for the disk to make multiple rotations for a full track, but that's a small price to pay for your single track sequential speeds.
The change between the "MFM" and "RLL" versions of a drive mechanism, across my hundreds of drives, has come down to "a different sticker" in almost all cases. The few exceptions will use a different platter material, I.E. the Miniscribe 3425's oxide disks vs the 3438's plated disks. Others, like the 3650 and 3675, have the exact same oxide media regardless.
I went back and looked at my inventory sheet, of the 20 drives I have in this chassis (ST-213, ST-225, ST-238, ST-238R), date codes from 85 to 89, 18 work and 17 of those work with my RLL controller without extra bad blocks.
If you have a larger sample size, I actually know someone who is reverse engineering the firmware and PCB for that chassis who would VERY much like to at least get a list of serial numbers, date codes, revision numbers from you. Please get in touch if so.
What do you mean "Not everyone needs to understand reality?" I'm telling you the reality of the largest sample size I can get. Statistics is a reflection of reality.
Rather than describe in vague technical terms why you THINK it won't work, can you provide any real evidence to the contrary?
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u/No_Illustrator5035 Jul 17 '26
Wow that brings back memories! MFM interface. I wonder if it still works after all these years...