Commodore History - Disk Drives

So far in our exploration of Commodore history, I've talked tons about the various computers, but not such a lot about the disk drives. And to be honest, the disk drives were almost as important because the computers themselves when it decreased to how They were used, and that they also played a crucial role in why Commodore computers were never ready to evolve within the marketplace just like the IBM PC for instance. Commodore's disk drives started back within the days of the PET, with these large metal drives supported The IEEE-488 interface. Using some extra hardware, it had been possible to attach many computers to one drive.

For example, during this computer lab setup within the year 1980, you'll see multiple pets connected to one disc drive. This design made tons of since because the computers didn't really access the drive tons, and therefor this might save tons of cash and space. If you would like to find out more about the PET drives, I like to recommend you watch a video from 8-Bit Show and Tell on the subject, which I will be able to put a link to down within the description And so, for the remainder of this episode, I'm getting to be that specialize in the disk drives used with Commodore's home computers starting with the Commodore 1540. So, the VIC-1540 was the primary drive designed specifically for the VIC- 20 and it's IEC serial interface. It had been released in 1982 which was roughly 2 years after the VIC-20 had come to plug. Meaning, that originally, VIC-20 users didn't have access to a disc drive.

Although, a year earlier Commodore did start selling a cartridge which might allow a VIC-20 to use a PET drive, but that was probably not a standard solution. That was okay, however, because the simplest software for the VIC-20 attended come on cartridge because these could delay to 16K of ROM. Software that came on cassette or disk would need to be loaded into RAM and therefore the stock VIC-20 only had about 3K to spare. Granted, you'll get memory expansions, but as We discussed before, most software developers would like to focus on the stock system as that was where the most important user base would be. The cassette drive was cheap, and with 3K maximum file size, the speed wasn't even much of a problem As such, disk drives were a touch of a luxury item for VIC-20 users and really only the clique users bought them.

However, an equivalent year the VIC-1540 disc drive came out, so did the Commodore 64, which also shared an equivalent disc drive interface with the VIC-20. However, the 1540 wasn't compatible with the C64, and reason may surprise you.

It was too fast. That's right, and if you've followed the series up to the present point then you almost certainly remember that Commodore drives were notoriously slow compared to the remainder of the industry thanks to a bug within the original VIC-20. Despite that, the drive was still too fast to figure on the C64 and therefore the reason may surprise you. If you've ever watched a VIC-20 load a program from cassette, it's like this. Not much to actually say, actually. But if you watch a Commodore 64 load a program from cassette, you'll notice the screen goes blank. Now the rationale for this has got to do with the VIC-II video chip utilized in the C64. It shares every other cycle with the CPU, very similar to the VIC-20 does.

However, within the C64, it steals quite just every other cycle. On certain scan lines, it steals even more CPU cycles than usual. We typically call these bad lines. Watching the clock speeds, you'll see the PAL C64 is certainly slower than the VIC-20, but the NTSC version looks a touch faster.

However, what isn't really explained by these numbers is that the effect the bad lines have. Since the CPU clock speed takes a dip every 8 scan lines, the C64 actually gets less work done than a VIC-20, what's worse because the clock isn't running at a stable rate, it makes things like serial timing routines much more difficult. So as to take care of compatibility with an equivalent cassette format, the C64 kernal will disable the video chip during loads, which suggests the CPU can run at a continuing speed.

However, when loading from disk, they didn't implement the screen blanking feature. Which suggests, the sole thanks to solve the matter was to form the disc drive a touch bit slower. And for this, the drive was changed to the VIC- 1541.

The only real difference between the VIC-1540 and therefore the VIC-1541 is that the badge on the front and a rather different ROM revision. Otherwise, these drives are identical. The 1540 wasn't manufactured for very long, and therefor they' re pretty rare and highly wanted by collectors. 

In fact, most of those that remain have had their ROM chips upgraded so they're actually 1541 drives that just happen to mention 1540 on the front of them. The C64 was initially treated much an equivalent because the VIC-20, with the first games being on cartridge and cassette.

However, it didn’t take long for the disc drive to actually begin, especially in North America. Things with the C64 was exactly opposite of that of the VIC-20. Cartridges still held 16K, but epitaxial a disk you'll load programs that would utilize all of the C64's RAM.

In fact, in some ways you'll even go further than that. A game might be much larger than 64K, and thus only loading within the parts that it needed when the time came. Thus games on disk attended have far more complexity, better graphics, and better sound than games on cartridge. And so, it didn't take long until Commodore rebranded the disc drive again, this point matching the color to the C64, and removing the VIC branding from the drive.

However, all 3 of those drives are still essentially the precise same plastic mold, same board inside, and apart from the 1540, they even have an equivalent ROM. Although the 1541 was sometimes distributed with different drive mechanisms, so this one for instance features Both styles are quite common. As we've talked about before, the commodore IEC interface is simply a interface. And while it's notorious for being slow, it did have some significant advantages over competitors of the age. And it contained its own DOS. Thus the pc never needed to understand anything about the physical media that was getting used. All the pc did was request a file, And therefore the drive would deliver that file. This meant the pc didn't got to allocate any RAM area for any kind of DOS like an Apple or IBM PC would have needed to try to to.

It also meant there was no got to disassemble the pc and install a control card like an Apple or IBM. And surprisingly, it also meant you'll in theory use a spread of media types, including hard drives, or differing types of floppy disks This was very true when accounting for multiple drives on one computer. These drives were also notorious for overheating, especially when people. That's mostly because the drives also contained internal power supplies that produced tons of warmth. Back within the 1980s, nearly every computer used a special disk format that was incompatible with everyone else. Commodore was no exception. ..

They used a format referred to as GCR. This suggests that for each 4 bits of knowledge written to the disk, actually 5 bits were written. This was done to stop any situation where quite two zero bits would occur during a row. An easy lookup And while this seems inefficient, it had been actually more efficient than many other systems of the time. Commodore also did a couple of other things. different from everyone else.

For example, on a typical IBM formatted disk, there are an equivalent 9 sectors on the inner tracks as there are on the outer tracks because the disk spins at a continuing speed, and therefore the read / write speed of the top also remains an equivalent . Commodore, on the opposite hand, used a system were more data was written to the outer tracks than to the inner. Therefore the inner tracks have 17 sectors and therefore the outer tracks have 21. This actually made more efficient use of the disc space ..

Another interesting thing is that the majority computers store the directory information starting at track zero, but Commodore drives stored it at track 18. This was probably done to scale back seeking time because the top would always be within 18 tracks of the directory track. The intended thanks to list a directory was to truly load a file called dollar sign from that device number.

This actually causes the disc drive to construct a special BASIC program that you simply can list, which can show the contents of the drive. The most problem with this design is that it'll overwrite whatever program you've got in RAM, so if you were within the middle of writing a BASIC program, you couldn't actually list the directory of a disk. In fact this wasn't an enormous problem since most Commodore users invested in some kind of fast load cartridge, and each one among them Added a feature where you'll just A short command to urge the directory listing without overwriting your BASIC program. Filenames might be 16 characters long and will be one among 5 file types. PRG files were program files and far and away the foremost common, SEQ were sequential files, or essentially text files. REL files are relative files, which are kind of like primitive database files.

USR and DEL files are pretty rare, and doubtless not worth talking about here. Also you'll store a maximum of 144 files on a disk, which may be a limitation of the directory, although that's a barrier few people ever encountered. Also, Commodore DOS isn't hierarchal, meaning there are not any sub directories. And files are always displayed within the order they're written to the disk, so there's no alphabetical order. If you list a directory and ever see an asterisk next a file type, that's called a splat file. Essentially these are caused when a file is opened for writing but the file isn't closed.

For example, if you pulled the disk out while writing a file, or if there have been a program crash or an influence failure. One interesting fact about Commodore DOS is how it handles the situation of the top. Most disk drives used sensors to work. out the top location. Apple disk drives eliminated the sensor to scale back cost and instead just sent the top back 40 tracks whenever the facility was turned on, usually causing the top banging sound. This ensured the top would be at track zero before any access Well, Commodore drives also had no sensors, yet they don't bang their heads whenever you power them on. So how does this magic happen?

Well, just one occasion you're bound to hear the sound is once you format a disk. Then, because the disk is being formatted, the track number is written to each single track on the disk. That way, even on a fresh power up, once you attend read a disk for the primary time, the drive will know exactly what track it's on by just reading the header to the track. So, under normal operation, you won't hear any head banging.

However, many copy protection schemes, also corrupted disks, could still cause the drive head to bang. And if this happened often enough, it could cause the drive head to travel out of alignment, during which case it might stop reading disks properly, and thus it might require service to realign the top. After formatting, listing a directory will show 664 blocks free on a newly formatted disk. So what proportion is that?

Well, a block is 256 bytes. So, 4 blocks is adequate to 1K. 

And, the 1541 drive only had one head, which meant you'll store about 170 Kilobytes per side. If you wanted to use the opposite side, you' d need to flip the disk over and it might be treated like a completely different disk. If the disk didn't have a write protect notch on each side, you'd got to punch one yourself and there have been special tools made only for doing that.

In 1985, with the introduction of the Commodore 128, Commodore also introduced a replacement drive to match called the 1571. Besides having a really different visual appearance, the 1571 also added many new features. It supported the C128's “burst mode” which meant it It also had 2 heads in order that it could read each side of the disk without having to flip it over. Now, initially you would possibly think that you simply could take a disk from a 1541 But, it doesn't work that way. The matter is once you flip a disk over during a 1541 the disk are going to be rotating within the other way. And so, to use each side of the disk, you'll need to format the disk during a 1571 as a double sided disk, then that disk can only be read during a 1571 from that time on.

However, when formatted, a blank disk would have 1,328 blocks free. So, twice what the 1541 had.

However, being that most commercial software wanted to target the 1541 for the widest compatibility, virtually no software was ever distributed on disks formatted for both sides, even software that was designed for the Commodore 128 because some 128 users were still using 1541 drives and never upgraded. Another benefit of the 1571 is that it had a track one sensor. This almost completely eliminated the head banging problem since it would always know when the head had made it back to track one, so there was no reason to keep trying to move it.

This helped over the long term with keeping the heads in proper alignment. And yet one more benefit of the 1571 is that the controller is more flexible and can read MFM formats as well as the Commodore GCR format. This allowed for compatibility with CP / M software. That meant when using with a Commodore 128, it was possible to read disks from machines like the Kaypro, for example.

However, this was also exploited to allow the drive to read and write disks formatted for IBM PCs, or MS-DOS. It required a special program on the computer side to be able to read the disks. And, just because you could read them But, this could be helpful for transferring things like text files from one format to another. And while a minor detail, the 1571 also introduced DIP switches to the back of the drive, so that And one last important benefit is that when a 1571 is attached to a Commodore 64, or a Commodore 128 that is running in 64 mode, the drive will also go into a 1541 emulation mode so that it will be compatible with any software designed to work in a 1541. During the early days of the 1571, Commodore was having trouble keeping up with demand in some regions. And so, as a stop gap measure, the 1570 was born ..

It used the same case molds as a traditional 1541, but on the inside you can see the board is essentially a 1571 board being held in place with some custom brackets. The drive mechanism itself is still a single-sided drive with just one head, but it does have the faster burst mode for the C128 and also includes a track one sensor. So, it's very much a hybrid between a 1541 and a 1571. The 1570 drive is pretty rare these days as it wasn't made for very long . 

Interestingly enough, you can actually see a 1570 on the floor in the movie Ready Player One. Of course, after Commodore switched to making the 64C instead of the bread bin, they also changed the 1541's color yet again, back to a white or light beige color.

They called this the 1541c, although there are no actual markings on the drive referring to it as such. It is essentially identical to previous 1541 drives except for the color and the badging.

However, shortly after they introduced the 1541-II. This has the same external design language as the 1571, but as you can see it is quite a bit smaller. It's also quite a bit lighter. And while functionally, it is identical to the This greatly improved the issues with heat buildup inside, which made the drives considerably more reliable. And, it also does have dip switches for The device number. The 1581 was introduced in 1987, well towards the end of the 8-bit era. 

This drive uses 3 and a half inch, double density disks. Because very little Commodore software would ever be distributed on this format, the main benefit of this drive was that it had a lot of storage on a single disk. A freshly formatted disk would have 3,160 blocks free. That was a colossal amount for a Commodore machine, as that would be roughly five times what you could store on a 1541 disk.

As such, these were popular with BBS operators, often having more than one of these drives, giving their file transfer section a lot more files to pick from. They were also popular with people who used GEOS, especially GEOS 128. They could store a They could also read MS-DOS formatted disks, just like the 1571. Again, they couldn't read this format natively, but with the use of a special transfer program on your computer. 

Despite not being directly supported by any games and virtually no commercial software, they were very popular with hobbyists and BBS operators and power users and therefor these are highly sought after today and they do tend to fetch top dollar when they show up For sale. Also worth mentioning is the Commodore 1551 disk drive, which was made primarily for the Commodore 16, Plus / 4, and other TED based computers. While using a traditional 1541 case mold, the 1551 gets rid of the serial port and plugs straight into the cartridge port of these computers. This did solve the speed problem, of course, as these drives were very fast.

However, they do not work on the Commodore 64, or the 128, or VIC-20 because they do require the custom cartridge port of the plus / 4 or the C16 or 116 or any of the other TED series that are out there. In fact, these drives are pretty rare because even the TED machines had standard serial ports just like the 1541 and so those users wound up using standard disk drives more often than not. So, these are actually pretty rare and fetch top dollar when they do come up for sale.

Up to this point every drive I've shown you has been actually manufactured by Commodore. But, what you may not know is that there were also numerous third party drives developed by other companies that were compatible with Commodore's ecosystem. So, each one of These 3rd party drives has at least one or two interesting tidbits or things I want to tell you about.

Let ’s start with the MSD drive. This is actually one of the first drives. This thing ’s actually really heavy too!

Now, this is actually a dual drive. It has two drives in the front of it. They also made a single drive version of this, which I do not have. The MSD SD-2 is an industrial looking drive with a metal case on It. 

This particular one has been molded with toggle switches to set the drive number, a practice I am not fond of, especially when placed right on the front like this. There is also a drive reset button. There's another toggle switches on the rear That I am not even sure what purpose it serves. Then it has the regular two serial ports like any Commodore drive, but also has an IEEE-488 port so that this drive can work with the PET computers as well, which were still popular at the time of this drive's release.

In fact, it shares something else in common with the PET drives, which is how it handles having two drives on the system. To demonstrate this, I will insert Planet X2 into drive zero and then Ghostbusters into drive one. To get a directory from And yep, there's the directory for Planet X2. And then to get the directory of drive 1, you just type this, and again, drive one will fire up, and there's your directory.

Of course, to actually access a specific file, you must place a zero or a one, followed by a colon, then the file name. Or in this case, I'm using an asterisk to represent the first file on the disk. Now If no drive number is specified, the drive will usually assume drive zero. So, some software will fail to load correctly from drive 1. The problem with this is, of course, some software will have to load in additional files afterword's. 

MSD drive was popular in the early days for BBS operators, because they could store essentially twice the amount of data as a single 1541 disk drive. They were also very popular at copy parties, because they were designed to be able to copy from one drive But, moving along, I want to talk now about the Indus GT. The Indus GT has a very refined outward appearance, as compared to the industrial look of the MSD drive.

The front face is supposed to open by pushing the button, but mine needs a bit of help. Of course, the cover doesn't really do anything other than just look cool. On the rear, it has the two Commodore serial ports and then These mystery “auxiliary” ports, which nobody knows what are for. Even the manual says they are for future use, whatever that means. 

Then there are dip switches for setting the device number. Oh, and as you can see it uses an external This is how the drive ended up being a good bit smaller than the 1541 of the era, and probably helped keep it from overheating as well. When powering up, you may notice it has a little 2-digit screen here. does a few different things.

For example, it usually shows the track number, so if I tell it to load the directory you will see it jump to track 18.

Of course, there is no disk in the drive, so I can show you the second use for it, which is displaying error codes. You can look these up in the manual, but over time most people would remember the common error codes. This But, I think the most fascinating thing about the Indus GT is its built in ROM drive. The way you access it is just like a dual drive such as the MSD I just showed. So, if you load dollar sign one, like this. You'll get a special directory of files stored in the drive's ROM that you can load. You can load the first one like this, which stands for fast IO and DOS wedge. And so, what this does is essentially like a fast load cartridge, it replaces the internal drive commands in the C64 with easier to use features and faster loading routines.

For example, you can use a slash to load a regular file. And, in this case, since I still haven't put a disk in the drive, it will also display the error message on screen without even asking, which is pretty neat Although, you can also use the at symbol to check the drive status as well. You can also get a directory reading like this, without erasing your BASIC program. So, all pretty useful stuff. And you may be wondering what the Fast Copy Well, as you can see, it's a full disk copier. Not very fancy, but it works. I should also mention that there was an Atari version of the Indus GT, which I believe was actually made first, And as you can see it looks exactly the same in front, but on the rear it has the Atari SIO ports instead. So buying an Indus GT drive would be kind of like buying a Commodore drive plus a fast load cartridge.

Although, granted the fast load cartridge would probably be a little bit more convenient because with the Indus GT you do have to type a command every time you power on the system in order to get access to the fast load features. Now, before I talk about the next 3 drives I need to talk about a little problem with making drives completely compatible with Commodore computers. You see, the protocol used by Commodore's IEC disk drive port is pretty simple.

It wouldn't be hard to build a 3rd party device that would allow users to load and save files over that protocol. The problem is that the 1541 is itself a computer and it is possible to upload code into the drive itself to change the behavior. This is how all of the fast loaders work, and it is also why you can run the drive music program, unplug the disk drive from the computer and the drive will keep making music on its own. It's also how certain copy programs would allow you to unplug the drives from the computer and the drives would continue to copy any disks you insert into them on their own.

However, this feature was also used by many copy protection schemes. In fact, many games used entirely foreign, non-standard disk formats. Only track 18 needed to remain compatible with the Commodore format, just enough to load the directory and the first file After that, the rest of the disk could be an entirely foreign format, designed specifically for that game. After a few years on the market, practically every piece of commercial software was completely dependent on the 1541 disk drive being exactly If you changed any part of it, it would break compatibility with hundreds or thousands of software titles. That includes the ROM code. So, while it would be easy enough to design a disk drive that would be compatible enough for users to load and save their own programs to disk, in order to be a commercially successful product, it would need to load commercial games. This presented a problem for third party drives. They could copy the design of the motherboards easily enough since they were mostly off the shelf parts.

But the ROM code was the biggest barrier to creating a fully compatible disk drive. Some companies, like the Excelerator Plus, simply copied Commodore ’s ROM code as is, and as you might expect, they were sued by Commodore for it. So, they agreed not to use their own code, but what they really did was take the original ROM code and swap around some of the bits, which changes all of the values ??to look like nonsense if you were to read the chip in an EPRO programmer.

However, in order to make the chip still work, they just swapped around the matching traces on the board so that it all ended up making sense in the end. Of course, Commodore quickly figured this out and sued again, eventually taking this drive off the market. It's often discussed online that many of these drives, if not all of them were targets of lawsuits by Commodore at one point or another, but the truth is in my research, I was only able to find specific information about the lawsuit against the Excellerator plus. So, while it's very possible Commodore may have sued the Enhancer 2000, or the Indus GT, or the MSD drive, I just don't know for sure. It wouldn't surprise me, but I just can 't find any information on it. The enhancer 2000 was a very common 3rd party drive that seemed to be mostly 1541 compatible.

There's not a lot to really say about this other than it's the only 3rd party drive that matches the color scheme of the bread bin C64 And the last drive I have here is the Blue-chip drive. They actually made several different models, but this Is one of the last models they made, and the thing that makes it unique is that it is actually not a clone of the 1541, but rather it is a clone of the 1571. So this drive was targeted for Commodore 128 users, and it supports all of the features of the 1571. And there ’s one very important 3rd party drive, which I don’t have, so I ’m going to let Robin from 8-Bit show and tell, tell you all about it.

Hi, it's Robin from 8-Bit Show and Tell. I have here the Creative Micro Design FD-2000, which is a 3 and a half inch high density drive. It's much like Commodore's 1581 but that only accepts double density disks. This also It formats the disk to 1.6 megabytes, which is almost 10 times as much as a Commodore 1541 can store on one disk side. The FD-2000 is a little smaller than the 1581 in width and depth, and it has the same serial ports, allows configuration of up to 16 different device numbers, and is powered by 9 densities DC. Using the included FD utilities program, you're able to partition the disk into several smaller 1541, 1571, or 1581 partitions, as well as program the optional real-time clock.

There is also an FD 4000 model available that that used the rare ED disks and could store up to 3.2 megabytes, but I don't have one of those. But, I do have something even more rare, this is a dual FD-2000 As far as I know, only 3 of these were ever made. You could almost call it a prototype, but it's more of a custom build that was used for disk copying. You can see on the included disk, make master, for use only with the FD copier, a custom version of the FD-2000.

The case is kind of ugly. They took a regular FD-2000 and just added this extra bracket on the bottom here. And on the back, it's even open. This was used by Loadstar for duplicating their monthly disk magazine. So, it made thousands and thousands of copies very reliably for Loadstar. I'll be doing a more in depth video about this disk drive in a future video on my channel 8-bit show and tell, so please subscribe.

Unlike 10 years earlier, by the late 1980s, compatibility was a driving force in the computer industry. Nobody wanted to produce products or even buy products that weren't compatible in some way or another. And because the vast majority of games utilized special disk formats and copy protection on the 1541 disks, that meant a 1541 or 100% compatible disk drive was a requirement for owning and using a Commodore 64. Unlike IBM PCs, for example, which rarely ever used this sort of copy protection.

In fact, by this time, most IBM compatible games were more or less expected to be copied or installed onto your hard drive for execution. But this simply wouldn’t be possible with Commodore software because they were so heavily intertwined with the 1541 disk drive. And, while this initially made Commodore happy because they were able to sue other manufacturers trying to create 100% compatible Commodore drives, it also meant they sort of painted themselves into a corner because the Commodore 8-bit line And, like I said, it's probably not the only reason for the decline of the Commodore 8-bit ecosystem, but it would never be able to move beyond the 5 and a quarter inch floppy disk unlike competitors like the IBM PC, for example. was certainly a contributing factor.

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