FM is RLL, MFM is RLL, RLL is RLL! Fight me. 

As someone who designed hard drive controllers when this tech was new, you are right - FM, MFM and RLL are all RLL. However, the quality of the oxide needs to be a whole lot better for "RLL" to work well. Formatting needs to write new address marks (which begin sector marks and data). Sector marks are a bunch of data which tells you which sector will come next (ie contains the track number and sector number). However - the address marks and sector data may be interleaved - sector label 1 is followed by data for the last sector, then sector label two, then sector data one! This is because the formatter processor may not be fast enough to figure out which label it just read in the inter-sector gap! I warn you - address marks are a possible problem: Mostly people used the IBM address mark. Unfortunately the IBM documents were wrong! The data bits were defined in chronological order, but the clock bits in reverse chronological order. I designed a controller with the clock bits in the correct order (as an option). Using the bits in the correct order means that the address mark contains a single flux transition in between two gaps exceeding the max legal distance in legit data. This means it is a unique pattern on the drive surface. The industry standard version is illegal as data, but is not necessarily unique. Using my address mark, most drives had enormously fewer bad sectors and read errors - but were not compatible with formatters made by IBM, Western Digital etc. I used programmable logic (which was new at the time) to map data into RLL code . In addition to formatters for mainframes, I also did the first hard drive interface for the Apple ][, and one for the BBC micro. Both used the 6502 CPU - like Woz did for the floppy controller!

Yes, I was yelling "You have to sys the drive." Or, you can format and sys the drive with the format C: /s command. Great video.

Sure, hundreds of us neckbeards were shouting SYS C: at the telly (or even FORMAT /S), but, and this is important, hundreds more didn't have the first clue so it's excellent that you're showing this to the inexperienced :D

Before MS-DOS 4, the sys command required the disk to be freshly-formatted. Starting with MS-DOS 4, the sys command was able to handle files already being on the disk.

36:02 You're welcome, it and it WAS an absolutely blast!

Yay! 30:47 indeed we were screaming "sys c:". I'm so glad that at LAST I had some relevant knowledge for this channel 🤣

Everyone else living in a rural property in Texas has a "ranch," whereas Dave has a "compound"

The thing with the SYS command, the IO and MSDOS system files is hardcoded to be the very first two files on the drive. The reason for this is because the libraries for handling the filesystem is inside those, so the DOS boot code can't go searching through the filetable the same way you can after DOS is loaded.

Those older Western Digital controllers have jumpers to set the drive type. Since you originally had a ST-238R in there, it's treating the ST-4097 as a ST-238R which means it formatted it with 615 cylinders, 4 heads, and 27 sectors. The drive types are defined in the ROM on the controller itself and it probably doesn't support the ST-4097 at all. There is a utility called SpeedStor that has a command line switch to display the drive types supported by the controller. Later WD controllers offered a free format option where you could enter in the correct drive parameters for the drive. The drive interleave is how the sectors are laid down onto the drive during the low-level format. A 4 to 1 interleave will skip every four sectors. The reason for this, is the 8-bit controller is not fast enough to process an interleave ratio lower then 4 to 1. I you were to tell the controller to use an interleave ratio of 3 or lower, you would end up with extremely slow drive performance as the controller would fail to read the next sector in line and have to wait for it come back around to try again. This would result in a 27 to 1 interleave ratio meaning one sector read for each platter revolution. If you were to toss in a 16 bit RLL controller like a ST-21R, you would be able to run a 1 to 1 interleave and should see 7 mb/s drive through put. There is even more tweaks that can be done during a low-level format such as head an cylinder skewing. Which affects how the sectors are positioned on the adjacent platters so when the head switches or moves it doesn't have to wait for an entire platter revolution. Without skewing, a fast drive like the ST-4097 will be faster with a 2 to 1 interleave vs a 1 to 1 interleave. You may also want to check out the ESDI interface which extends on the ST-412 (MFM / RLL) interface. ESDI is not compatible with the older ST-412 interface drives.

Brings back memories of my first PC in 1988, running Debug to low level format a 5MB Rodime HDD I bought second hand.

Always find hard drive stuff very fastening. Plus I want to thank you and your discord team for helping out Adrian's digital basement. 👍

You have experienced, "Low level format" using the ROM on the controller that is at at memory location C800:5. Then the "partition" using fdisk. Then the "high level format" using the format command.

I like the part where they make sure that the SD card is mounted and then writing the raw image to the onboard storage. 😂

I did a similar thing in the early 90s. I got two MFM hard drives (one full height and one half height) basically for free, as there were considered old, loud, large and slow by then. I learned about RLL and that using that would make the storage capacity some 50% more and reading the drives would be faster. I was happy to have the extra storage, and my tower case has enough slots for the huge disks. But man, were those drives noisy...

You've low-level formatted the ST4097 with the drive parameters of the ST238R, so you'll only have 30MB usable. On these older controllers you have to select the drive parameters with jumpers. They depend on the Controller's BIOS ROM version though. There are lists online of which ROM version supports which drives. It's quite possible that your ROM won't support the correct parameters, so you'd either have to modify it and change the parameter table, or get the WD SuperBios which can be configured to any drive parameters. The ST4097 is a 80MB MFM drive, so with 2,7 RLL it should give you roughly 120MB!

Ok.. the moment he mentioned Procomm Plus, a wave of nostalgia hit me like an ocean breeze.. All the BBS i've spent time on came back to me.. lol That is just awesome!

Lol, I just knew AJ from Knight Rider Historians. I had no idea he was into vintage computing.

As an old EDS'er I smile when I see that logo.

I was a PC tech and owner when the RLL controllers came out. While everything official said you needed a rated drive (at least to be supported), common knowledge was that most decent MFM drives could be re-formatted using an RLL controller for a ‘free’ 50% increase in storage space. I bought an Adaptec RLL card, and successfully used it with a ST-225, and a Miniscribe (also a hh drive) and had twin 30meg drives. Later replaced with a giant Maxtor full height that formatted out around 200MB, unheard of for a 8086 box. BTW, aside from the Falcon controller made by Tim Patterson, the fastest a 8 bit MFM or RLL controller could manage was a 2:1 interleave. 1:1 overran the bus unless you knew the magic Tim did. I still have that Maxtor and the controller along with the Compaq deskpro, not powered up in years. I need to image it, so getting that magic board to support RLL would be really exciting to me.

Oh man that took me back 30+ years to playing around with my Amstrad PC1512 and then PC1640 machines. Formatting hard drives, swapping floppies back n forth, trying out copy commands, learning about Autexec.Bat, Config.Sys, XCopy, editing files, trying and failing, then trying and succeeding etc etc. What amazing days they were 🥰

Oh, memory lane !!! Thanks for the video. One thing about the MFM vs RLL thing that you missed (not because you were wrong) is that those differences came along because of software, not hardware. People started noticing that there were better ways of encoding things, hence the LZW algorithm that gave us ZIP and DCT (Discreet Cosine Transform) that gave us JPEG. That is where this magical way of encoding stuff came from, if you encode it like that, you are able to compress more stuff together, both being able to store more as well as being able to read/write faster. Once again, Thanks for the video.

It warms my heart to know that there are still ST-238Rs alive out there in the wild. Not extinct yet! Dave, remember the only reason anyone ran the 238 vs. a 225 was the 50% more capacity (30MB vs. 20MB) at an incrementally higher price. Not sure why EDS would spec a 238R in the machine, I guess they needed the 30MB capacity? Otherwise, the 225s were as common as cigarette butts back in the day.

Instead of using format c: and sys c: you can also use format /s c: and transfer the system files as part of the format. Also, ensure that the partition you want to boot is active. From what I recall fdisk from dos 3.3 will take care of that, but it is something to always check.

It's just because there is no separate timing signal, and the oscillator/clock with the disk writer and disk reader won't be synchronized. A device called a phased-lock-loop is an oscillator where you feed back the received signal into it to force the local oscillator to drift into alignment with a signal and when the signal drops out (or when there is a gap with no transitions) the local oscillator in the PLL will keep on ticking as long as not too much time passes before a new transition to re-synchronize. This allows the signal to contain several similar bits crammed together which represents no transition. Other ways to do this without a PLL would be to have start and stop bits like serial but that would be unideal.

A couple things. 1) You should copy all the dos files to a dos directory and the procom plus files into a procomm directory. There is a limit to the number of files you can have in the root directory. I forget exactly what it is, but it isn't that much and it's probably less for dos 3. It will generate false disk full errors if that number is met. Second, you should probably create a config sys file and an autoexec bat file with a decent files= statement and load ansi sys (both in config sys) and a path statement in the autoexec bat and a prompt=$p$G for a normal looking c prompt.

FYI, an ST238R is simply an ST225 that passed a few more QC checks. Quite a few hobbyists with ST225s plugged in an RLL board and got the 32MB capacity with no issues.

You can run MFM drives on an RLL controller and, back in the day, be very happy getting 50% more space, but there's a cost. As the drives heat up, you can end up getting more and more read errors since the disks aren't really rated for that kind of density. The drive may last a couple years running like this, then the errors start. I ran into this with a couple of ST-225's. Both drives started with read errors about 2 years into their lives. It got to the point where they were so hot, I couldn't touch the drives after 30 minutes. I really had to copy the data off of them, but to keep the drives running cool enough for long enough, I had to run the drives under a towel and a gallon bag of ice water. Worked like a charm!

I know a lot about the ST-225 / ST-238 , rotation speed stability was the difference as RLL needed better control . The ST-238 is a ST-225 that passed testing . The ST-238 is sutable with modifications for video image file of one digitized with ( PWM on disk ) NTSC frame per track a quiet revolution at that era : )

Brings back memories a:\format c: /sys is a shortcut to put system files onto new boot drive in a single line when formatting

All Hail Ross Perot! (that noise is the sound of our souls being sucked out by the floppy)

As a couple of other commenters have already said, if you want to get more than the 30MB out of the HDD you will need to low level it again after changing the jumpers on the controller card. The exact parameters for the 4097 are unlikely to be supported, but you can pick any larger geometry which has less than or equal to 9 heads and less than or equal to 1024 cylinders. Look up the model on the controller card on bitsavers or TH99 or similar and find a manual. The supported types should be enumerated in the documentation.

In my old 286 system I had a Seagate ST238R HDD controller. I ran several different MFM drives as RLL with absolutely zero problems.

Nice shirt! We spoke briefly as VCF SW. I actually have one of the world's largest documented collections of vintage mechanical hard disk drives, I'm still counting spoils fron VCF, but I think I am around 600 units right now. FWIW, MFM and RLL drives are not often called this way by collectors, they are ST-506/ST-412 and ST-412HP, or 5MT and 7.5MT, respectively. The only difference is the expected encoding, which for most drives was entirely determined by the method used to test the drive in the factory. If it passed with few enough defects as RLL, its an RLL drive. The ST-238R is one of these drives. It is an ST-225 that you were at one time guaranteed for compatibility with RLL. You can run it as "MFM," or if you have an ARLL card like a Perstor PS200, you could run it at 10 megabits, or if you hitch it to an arduino, you can write one bit per track in a custom format. The drive does not know or care about the format at all. I have tested every drive in my collection as RLL - Every video demo I have done is with a DTC 7287 cached RLL controller. I have yet to find a drive that works with MFM but does not work as RLL. Even the ST-412 itself, and a myriad of crappy clones, even Soviet drives can handle it without much worry. I have personally tried one of those dingy little emulators - I borrowed one from Forgotten Machines, actually, and I was not able to read any drives formatted with my DTC 7287 on it.

Brings back a lot of memories. My first PC was one very much like the EDS, with twin 40mb RLL drives. It ran DOS 3 and it was basically plunked down in front of me to figure out. Eventually had Procomm Plus on it as well. That software was insanely powerful. At one point, I had it running as a BS host for other people to dial into, before eventually just running a real BBS of my own. Procomm Plus was my killer app during that whole era. Still have the floppy somewhere. Seeing it on your channel is like seeing an old friend again. Also surreal seeing AJ on here. That guy gets around!

You need to copy all the DOS files into a directory usually called "DOS", because the number on entries i.e. files in the root directory is limited. The error message is a bit useless since it will only say something "not enough space left..." when it actually should say "not enough file table entries left..."

The sequence is as follows: 1) Low level format: debug g c800:5 to run the BIOS provided on the extension card The sector interleave is the sector count between consecutive sectors on the same track. This value depends on a whole bunch of factors, the most important one being the speed of the CPU. Because of the sector skipping the transfer rate decreases The value of 4 means read one sector skip 3 and read the 4th one etc... For an XT class machine it is probably the right value. 2) Use Fdisk to create 1 Primary dos partition (the only one Dos can boot from) 1 extended partition that will itself contain as many partition as necessary 3) Dos format letter: /u (/u = unconditional do NOT retain previous data structures) The /u switch is only applicable for recent revisions of Dos (5 and up ?) 4) Transfer the system with the 'sys drive:' command From a: with a bootable disk in it run sys c: 5) Copy the rest of the files with copy (or xcopy if available) Putting all dos files under c:\dos is considered good practice Only the 3 system files (see bellow) and boot configuration files (config.sys, autoexec.bat) should be at the root of C: PS: the system files: IBMBIOS.SYS IBMDOS.SYS COMMAND.COM are supposed to be at predefined file allocations positions otherwise the boot process will stall. The sys command does not support "making room" for these files by moving files elsewhere. This is why the sys command has to be applied first, before other file can use up that space. PS2: you might want to give ms-dos 5.x a try to break the 32Mb per partition barrier if the ram size allows.

Love the excitement you both display when something works. I've been in the same position decades back and your chuckling brought back those days.

Two thumbs way up for Dave's emulator. When the hard drive on my Kaypro 10 died, I bought one of these. It was close to plug-and-play to install and the old Kaypro restore disks had no problems with it at all!!

You have a great knack for simplifying and explaining all of the tech jargon. Extremely fun entertaining and educational channel.

Interleave indicated how many sectors should be placed *between* sectors in a given sequence. Why does that matter? Because if you were reading sequential sectors, the processor would take some amount of time to transfer data to the PC. This means if you ordered them [1,2,3,4,5,6,7,8], by time you transferred the data after reading sector 1, the head may be physically over sector 4, or 6; and you'd have to wait for the drive to spin back around the start of sector 2. If you get the offset right (say it was optimally 3 or 4 sectors), then an interleave of4 [at least] would put 4 sectors between each sequential one to get the best response time. That would give you an order like this: [1,3,5,7,2,4,6,8]. This way by time the system is ready to read the next sector, sector 2 is the next one to hit (or the one after, worst case). If it hit a conflict when building the map, it would just push to the next free sector block, and continue that pattern until the sector list was full. Worst case, some end sectors have slightly worse performance, but it' still way better than an interleave of 1 (which is how most early drives were formatted). There was a tool called "spinrite" that would copy out, then low-level at about 20 tracks in with different interleaves to find the best one. It would err toward the larger number, and then re-low-level format the whole drive with that offset. (Later versions would change interleave several times over a larger drive, since the value could change based on track velocity and density.) This would cause at least that first area of the drive to be perfectly interleaved. Since that's where the boot, system, and often the MFT lived, it made the boot sequence, and the entire performance of the filesystem significantly faster when properly tuned. Mind you: some drives did not support this low-level rewriting. Many RLL drives would forbid it, since the read timing was so critical that it couldn't be relied on for that track data to be written out in the field. The equipment needed to do the timing properly was far more expensive, and was only found in the factories that made the drives. By that point though, manufacturers were optimizing interleave anyway before production, and drives started having buffers to optimize the transfer to the system. Some early RLL drives mistakenly left the low-level write code in though, and triggering it would just nuke the entire drive. Guess where your ST241 lands in that! If you guessed "nukeable with spinrite", you'd be correct. I know that one from painful personal experience.

David’s MFM emulator’s are awesome!!! I have maybe 8 of them!!! Truly amazing MFM solution!!!

Love the B-W Corsiar-2 photo print on the wall. Great show... thank you.

I like this AJ guy! good sense of humour. I love how the software reports runtime with nanosecond resolution :)

Data recovery specialists! Nice work :)

Usually format C: /Q /Y only write an empty File Allocation Table and does not ask for confirmation. This is time saving not to cycle through writing all the cylinders.

This is awesome! Thanks for the heads up about AJ!

I used to use MFM drives with a RLL controller back int the 80s without issues to save a bit on the cost of RLL certified drives which were more expensive

Post credits sequence?!! Oh no, have I been missing these every time? 😁

Awesome video as usual! The baby rabbit at the end was adorable!

Loved getting a chance to see these in operation in person

Very impressive and compelling episode!

This reminded me of the Perstor 180 and 200 series disk disk controller boards from the late 80s (I think). They used a more aggressive RLL coding, which would allow pretty much a capacity doubling relative to their MFM capacity, rather than the extra 50% from the regular 2,7 coding that was normally used. Of course, they also required even better timing stability in the recovered read data signal in order to operate, but by the late 80s more drives were capable of that level of performance.

I just love this channel

Love to see it work. Can't wait till you decode the transitions file!!

Interleave basically translates to "how many revolutions of the disk are required to read all sectors on a track". Smaller values make reads/writes faster until the controller's ability to read consecutive sectors is exceeded. At that point performance falls off a cliff because an additional rotation of the disk is required between reading/writing each sector. For old 8 bit MFM controllers on XTs, interleave of 3 was typical, but sometimes you could get away with 2, increasing performance by 33%. RLL usually has a higher interleave value because the sectors pass under the heads more quickly (26 per revolution rather than 17).

Procomm Plus was an amazing terminal modem software package for DOS! I used it ALL the time back in the day!

Back in the early 90s, I remember connecting an MFM hard drive to an 8-bit ISA Seagate RLL controller and I would get an additional ~30% storage after low-level reformatting the drive. The downside was that I noticed the drive would run hotter. Someone once explained to me it had to do with how it would run the actuator which was out of spec. So yes, I would agree from experience that MFM Is RLL and RLL is RLL.

This was very cool and the rabbit feeding at the end was the jerry on top for me.

This could easily have been an 80's video showing off the speed of the newly introduced harddrives! 😄 I love it! Nicely done David!

Just love this detective work!

Okay, I did not expect to see a Knight Rider Historian here 😃

Funny how I haven't done a lowlevel format of an RLLor MFM drive since the late 80s, but I still remembere debug g=c800:5. Crazy what the brain stashes away. I am loving your channel. It's got so much fantastic content. /spins propellar hat.

Your joy at 33:58 mirrors my own, back in the early 90s, when I first installed a hard disk in my amiga 1200. IT WAS SO FAST!!!

Procom plus has a BBS build into it. It was my first BBS as my dad had procom plus for work. Once I got my BBS going I switched to TriBBS. Back when I had a 8086.. Ah miss those days.

Boy this brings back memories. I even remembered the low level format entry point

Haha! Love the title of this video :D - There it was, you addressed the title fairly early into the video with a neat explanation. It has surfaced a long buried memory, I'm now trying to think whether I came across these encoding schemes as a student or afterward, lol. At any rate, it's really good to get these "vintage" techniques back in the light of day - thank you, Usagi (and today, AJ)! I'm curious to see what headway you've made with DEC's insanely brilliant PDP-11 power supply schema 😜

Back in the day, the telco I worked for used mainframes and mini computers for all IT, we used various terminals to talk to them. When PC's came out it was cheaper to use a PC clone as a terminal. We had a company supplying up with these low profile clones that booted from a floppy drive, however the user could not see it as it was hidden inside. The 3.5 inch drive was in a regular drive slot, but pushed back as far as it would go, then the blanking plate that came with the box was placed in front of the drive. This was not a problem as they were only booted at the start of the day - sometimes even less as slack employees often just left them on at the end of their shift. Booting gear from floppy was fairly common in the IT industry, we had these network controllers (forget the brand) that were dedicated controllers, not PC compatible in any way, that booted from 5.25 inch disks. Actually the floppy disk was originally invented by IBM to IPL a mainframe (Initial Program Load) and later got developed to what we saw later powering whole generations of computers.

Finally someone explains the concept behind mfm vs rll. I used mfm drives with rll controllers for such a long time with my Amiga 1000 and (Commodore) PCs until IDE showed up. Why? As kids we recycled broken drives by swapping parts around and used what we got. We basically never had problems with repurposed ST225, ST251 and the full size ones which model number I just forgot, which just worked fine with rll Controllers.

What a fabulous explanation... I've been throwing MFM and RLL around for decades... Now i can throw them around and actually know what I'm talking about. I love the plastic panel on the front of that drive... a half height cosplaying a full height drive. ;)

Nice work!

I love watching shows from the old days, And they speak about computers. This makes this clear to me.

You questioned what ‘interleave’ is. The sectors are not placed sequentially on the track, but have one or more sectors before the next sector in sequence (eg, 1,x,y,2,… would be an interleave of 3 (if I’m remembering correctly). This was done when the controller couldn’t keep up with sequentially written sectors, so rather than wait an entire disk rotation, they simply ‘moved’ the next sector a few sectors away to let the controller catch up. Eventually ‘all’ controllers became fast enough and interleave factors became 1:1. Love to watch your videos. A real trip down memory lane. Thanks.

Any drummers do a double take on that title?

Haha, I liked y'all's aplause reaction to this starting to work!

Wow! Looks interesting to see BBB as head of some repair tool.

Great Video, thank you! To format and make the disk bootable, you also can use the /s argument with the format command. 'format c: /s' lets the OS first format the disk, then copy the system files to it, as if you had run sys after formatting.

Back in the day, I do recall taking an MFM drive that was about 20MB and worked fine with it's MFM controller in DOS. I replace the MFM controller with an RLL controller to the same HDD then low level formatted it, but I'm not sure what software I used for that it wasn't using debug and jumping to a memory location. It was either a specific software from the drive maker, OR is was a format utility in CMOS BIOS that wrote zeros all over the drive. After that I mounted the drive with FDISK. Then formatted it in DOS (3.3 or 5 maybe?) and it gained 10-11 more MB! I then ran Norton Utilities to set it's interleave (1:1) so it would run a little bit faster. Interleave, from what I understand, was the number of times the disk would spin before it performed a read/write. The higher the interleave the slower the drive performed. Norton Utilities had a program what would test interleaves for your drive and find the lowest interleave that didn't screw data integrity. If it managed 1:1 (1 rotation : 1 r/w) then you have a very good drive.

Seeing a literal gray beard get flustered (and also thrilled) by old DOS stuff I still remember from my youth and Linux is kind of amusing and sweet! "I've never used fdisk before..this is new!"

I thought I was the last person alive that knew MFM and RLL

I got one of those MFM emulators recently, prompted by a recent video from Adrian's Digital Basement. Haven't used it yet, but hope to soon!

That's an incredible tool!

He called it a compound himself, so we can call it a compound too XD Great video

Idk why but the "technical difficulties" with the piano brake down killed me I wasn't expecting something that random upbeat and fast paced in the middle of all the interesting long winded info

ST238R, my first HDD!

Congrats! Your EDS now boots from the C drive, just like a modern PC!

MFM, RLL, Voice Coil termos que ficaram para sempre na memória da gente xD FDISK... Debug + G=100 + Entrar lista de Bad Sectors + etc :D fiz muito isso nos computadores, naqueles anos. A gente instalava muitos HD, apesar do preço ser alto. Duas coisas atrapalhavam as controladoras: Mau contato (Mesmo sendo novas) e aterramento. Sim! As fezes, só de colocar um parafuso, mesmo que fechando o gabinete, fazia a controladora ou a placa-mãe ficarem loucas! Vendo a situação, lembrei de um tempo em que alguns conjuntos (controladora+Winchester) ocorria um problema: Após formatar e transferir o sistema e dar boot, dizia que não havia O.S. para dar boot. Daí, tinha que executar o Sys c: novamente. Com o tempo, descobri o que era (não lembro mais). Bem, grato pelo vídeo!

In the mid 80s, I saved up to buy a hard drive from "Hard Drives International" for an IBM clone PC. ( I couldn't afford a real IBM PC as it was over $2000 back then). It would be my first hard drive, moving up from "floppy boots", and I was pretty excited. The drive I got was RLL, and somehow, I think the RLL drives were less expensive than MFM, which is why I got the RLL (they were expensive back then). Also, that was the first time I heard of RLL, and never forgot what the acronym stood for, but didn't know the tech behind it :)

My first linux box was a 386 with a pair of 20mb MFM drives that i had low level formatted on an RLL Controller to bump them up to 30mb each. Yes there were a lot of bad sectors but it still worked.

To format the harddrive and transfer system in one step you can use A>FORMAT C: /S but also to make your system disk look a little nicer you could place the dos files in a subdirectory by itself. A>MD C:\DOS and then copy the diskettes from A -> C:\DOS A>COPY 'star'.'star' C:\DOS (RU-vid won't show the 'star' character) to enable the system to find the dos files at the correct subdir you need to add following line to the AUTOEXEC.BAT file PATH=C:\DOS Maybe other ppl suggested this too, so I'm sorry if this would be a double entry. Very nice machine :)

"Idiot with a Hammer" sounds like a good band name.

That "insane" list of errors was actually common in late 80's when installing Netware. Can't remember the tool but we always had to run a program (sys?) to warn the os of the bad stuff. Then ages of figuring out if track 0 was reliable and then an age of checking the disk. Later versions could handle bad blocks dynamically shaving days of installing a server.

It's been 30 years since I played with RLL drives. I had a 21mb ST225 drive in a 286 running DOS. I do remember it had a clunky, nasty sound when it ran....

Dumping everything in the root directory makes my hair stand on end XD The contents of the DOS disks go in C:/DOS, then you put it in your path string

Blast from the past - thank you. I remember in the mid-80's buying a HUGE 72MB Micropolis drive and then RLL'ing it to 144MB. An yes, my piers thought I was insane for wanting that much storage. I won't admit what I paid for that (used!) 72MB 8" drive But I was successful and became "the man of the hour" Thank you for the infoTainment. The check is in the mai! Cheers from So.Ca.USA 3rd House On the Left.

How are you planning to do file transfer? Write an XMODEM program for the Centurion, and then use Procomm+'s file transfer support (which surely includes XMODEM)? I don't understand why different disk block sizes matter if you are backing up at the file level... Flashback to using KERMIT to transfer files from our VAX/VMS mainframe to my Atari ST in 1987ish...

20:14 Yes...cute! It was RIGHT THERE the whole time!

I had no idea Basic was invented in New Hampshire! As a native, I recognized the historical markers. So cool!

You put everything in the root of C:? You monster! 😂

Apologies I'm super sick watching this right now I might fall asleep but I promise to rewind in the morning

Only you get so excited over something so dull. And yet, I watched the whole thing on the edge of my seat.