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Converting a PC Booter Game to Cassette Tape

mogwaay

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Mar 5, 2021
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32
Hi all,

Just wanted to share my little show-and-tell YouTube video I made of my loading the old PC Booter game "PC-MAN" from cassette tape.


Here's the links to the repo with the WAV file (there is an MP3 file, but I actually haven't tried that yet!) if you want to give it a go yourself - I'd love to know if anyone gets it working on their IBM 5150 or PCjr as I don't have either of these machines and could only test that using the MAME emulation of both those machines:

https://github.com/moogway82/pcman_tape

I also have a little more information about the process I went throught to create it.

I load it on my own PC clone, the XTjr - it's a derivavtive of Serge Kise's Xi8088 and a few of his expansion boards with a bit of simplification and an additional Tandy 3-voice sound, more details on that here:

https://github.com/moogway82/XTjr

Anyway hope someone finds this interesting,
Cheers,
Chris.
 
I for one like seeing this project! Imagine being able to get use out of your cassette port for programs that should have been available for it back then. PC booters are a great choice too, since they make you have to reboot when you're finished playing (like those other computers that only had cassette storage).

Several years ago, I came up with the idea of burning audio CDs of cassette-based programs for TRS-80, ZX81 & Spectrums, Commodores, etc. Among the advantages are that you don't have to worry about tape (shrink)age altering the playback of the program, you can't accidentally record over the only copy of the program, and you can put each program on it's own separate track so that you can easily separate each program from the others. This is a great way to store your collection of published or finished programs for cassette-port-only computers.

Just imagine the updated product line that could have been launched in 1983-84: PC booter games on (audio) CD: the forerunner to CD-ROM games.

I can see it now, the first CD Arcade Game collection:
Astro-Dodge
Battlezone
Donkey Kong
Galaxian
Joust
Lode Runner
Paratrooper
PC-Man
Stargate

Just select the track your game is on, press play, and start loading.
 
Congratulations on getting that working. Amazing how the IBM PC cassette port received more development support decades after IBM canceled the line than when the PC was in production.

@acgs: You have described the dream behind the Advance-86A, a cassette only cheapest gaming PC possible in 1984 that could be upgraded to XT compatible status with a expansion case with ports and slots. Alas, with only 3 employees and a few thousand systems sold before IBM noticed the pirated ROMs, the chance for a sizable IBM PC gaming library delivered through audio was never realized.
 
That's unfair! Stealing a guy's idea 38 years before he thought of it. At least they didn't get the audio CD angle!

Seriously, though, I agree that the cassette port is ironically more interesting now than when it came out. I think mogwaay/Chris's XTjr is a great design for this kind of system. (He only needs to add :) a cassette port to it now.) It's somewhat similar to the Advance-86A (which I had never heard of before this), but more like the Commodore 8-bit systems since it's all under the keyboard.

This thread's original topic is really very much like some of the computer club programs you'd see in the 1980's. In fact, I remember seeing one that allowed you to copy the Cassette BASIC ROM to a file and use it to run IBM BASIC(A) on compatibles that (obviously) didn't have the ROM built in. Sort of like this program's concept in reverse.
 
@acgs I was a bit stunned that there didn't seem to be *any* games released for the 5150 or PCjr on tape - especially as it was a common interface to all those machines and anyone buying the basic 16KB version, loading from BASIC would've been pretty useful to make the most of the RAM. I guess that means that pretty much nobody did buy the diskless 16kb PC - or PCjr. Also in Europe there was compilation Audio CDs of games and for some computers - Nostalgia Nerd went through some of them a while back, for the ZX Spectrum and Comodore 64 I think:

I would like to try this process with more PC Booters - my retro tinkering time is always very limited and I have other projects I'd like to get around to, but if there's anything that anyone would like to try, I might give it another bash - maybe an Arcade Mega-Mix Tape would be cool, that list might be a nice starting point for a compilation!

@krebizfan I had never heard of the Advance-86A and now I'm REALLY interested :D - this sounds awesome and just like the kind of thing I was looking for. I'm also now really interested to know if this maybe turned into the Amstrad's PC1512 as there are some similarities - UK Based, 8086, cheap and I think Amstrad used Ferranti for their ULA, so maybe some overlap? Anyway, I'd love to see some schematics for the Advance-86A to see how it ticked and was upgraded to the Advance-86B - I poured over the PCjr and 5150 schematics (to extend and understand Serge's Xi8088 which was the main basis for it) when trying to build the XTjr - might give me some ideas...

I tried making a cassette adapter based on the IBM5150s, and the Apple II as I could just about understand them with my limited analogue electronics know-how, but these were both quite basic interfaces and it didn't work well for me. The ZX Spectrum +2A tape amp was a bit better and made it easier to get a good level to load from. Plus, it's the only tape deck I have that works at the moment!

Anyway ta for the feedback. I'm still super keen to know if anyone with an actual 5150/PCjr is able to load the tape file I made - anyone out there wanna give it a bash? VWestlife was a big inspiration for me with his video on (
) which give some good info on interfacing a tape deck to it.
 
Well buying a 5150 with no floppy drive would be like buying a luxury car with manual windows. It was a high end personal computer that was expensive to start with. Anybody looking for a cheaper option was likely going to buy a C64 or other home computer.

Cassettes are interesting from a historical perspective but for everyday use they suck. So if you are a software developer and 99% of your market has a floppy drive, you are releasing on floppy.
 
A 16K cassette only 5150 would cost more and be less effective than a 16K cassette only TRS-80 Model III. 8086 code would be slightly bigger and losing 1k to interrupts doesn't leave a lot of memory even for a minimal word processor like Electric Pencil. IBM also charged a lot of money for those empty slots and bays. Now, a 64K+ IBM PC with cassette could do more than the Z-80 counterparts but for business, the upgrade to disks was a no brainer. 64K takes about 6 minutes to load off cassette. For a hypothetical 128k text editing system, that would mean 6 minutes loading the text editor, 6 minutes loading the file, 6 minutes saving the file for lunch, 6 more minutes saving the file before leaving for the day for a total of 2 hours wasted each week. Not difficult to discover that floppy disks will quickly save money.

Cassette usage for IBM PC compatibles was an interesting oddity. Most of these systems I didn't know anything about until relatively recently. The Soviet Union had 3 or 4 cassette equipped PC compatible models with modest libraries of mass produced cassettes. Much of the software was translated copies of software available on disk before. Basicode had routines that could use the IBM PC cassette port or a parallel to cassette adapter for XTs or ATs to get radio broadcasts of software converted. The trainer MPF-1/88 could import IBM PC BASIC files from cassette; I don't know if there was any software on the 5150 side to assist with development.

https://nosher.net/archives/computers/your_computer_1984-05-004 gives a capsule history of the Advance-86. The price isn't too far off that of the Commodore 64. I can understand the impetus to designing it but I doubt Advance had the resources to pull it off. The Advance manual does have a section of cassette usage which is fairly interesting in a historical context. Someone saved a draft version of the Genie 16 documentation which was a proposed variant of the Advance for the German market. No copies of the Welcome cassette have been located.

CD players were too expensive to use in support of computers in the early 80s. 1984 was when Sony introduced the first $500 CD player. Floppy drives look quite appealing in comparison. The other problem is audio storage is inefficient at only 10kB per minute with the 5150 and similar cassette routines. Even placing different programs on the right and left channels still means only a little more than a megabyte could be stored. The CD instead of cassette was an interesting concept once the 90s and cheap CD players arrived but mostly would be gimmicky cover discs.

Lest I forget, there were two advertised sets of software on cassette in the US. AFAIK, neither was released in cassette form. One was MS's Typing Tutor as seen in 5150 catalogs. The other was Home Computer Magazine which offered the listings on cassette for the PCJr.
 
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Plasma and krebizfan make a good case against audio storage taking off on the IBM. Just in case anyone mistakes the tone, what follows below is not me trying to start an argument, flame war, or make personal attacks. I'm just proposing an alternate view of what might have followed IBM embracing the audio capabilities of their "capture-all-markets" microcomputer.

Well buying a 5150 with no floppy drive would be like buying a luxury car with manual windows. It was a high end personal computer that was expensive to start with. Anybody looking for a cheaper option was likely going to buy a C64 or other home computer.
A 16K cassette only 5150 would cost more and be less effective than a 16K cassette only TRS-80 Model III.

True, but people were buying IBM's like crazy back then and IBM seemed to feel it was necessary to offer 16K machines without floppy drives. (Indicating they had no idea where this was going to go or that they wanted to aim at all micro markets.) The PC could be hooked up to an existing TV, saving on the price of a monitor. It had the cassette port to hook up to an existing cassette player, saving on the price of other data storage systems. As a home computer, it was expensive, as was an Apple II. But, it was an IBM! Logic doesn't necessarily apply here, especially in the early '80s. I remember coming across magazines for kids with really simple IBM BASIC program listings in them, so kids could learn programming with the IBM PC at home. This shows at least some kind "recreational" home computer market existed for the IBM.

IBM also charged a lot of money for those empty slots and bays. Now, a 64K+ IBM PC with cassette could do more than the Z-80 counterparts but for business, the upgrade to disks was a no brainer. 64K takes about 6 minutes to load off cassette.

Did the cassette port ever seem like a viable business solution on any microcomputer? I think the cassette port was aimed at the home computer market. Upgrading only the computer's RAM to 64K+ and not adding disk drive(s) would be a cheaper upgrade and allow cassette programs to perform closer to their 8-bit home competition.

Cassette usage for IBM PC compatibles was an interesting oddity.

True. Why was it included in the first place? My guess is to make the 5150 a competitor to every micro on the market, no matter what target audience. Perhaps a hedging of bets to make the projected high volume of sales seem more believable to IBM execs.

CD players were too expensive to use in support of computers in the early 80s. 1984 was when Sony introduced the first $500 CD player. Floppy drives look quite appealing in comparison.

Yes. By 1984 the cassette port was essentially the IBM PC's/PCjr's appendix. No one seemed to really have done anything with it to capture the public's interest. But, if cassettes had already become popular, the CD player as a medium for software might have looked attractive to the home computer buyer. Not only can you play high quality music, but you can also use it to load video games, etc! If you were already going to spend the $500, you would get this option as a bonus.

Also remember: In 1987, when CD-ROM was really expensive, "Microsoft Bookshelf" was launched to promote/encourage the adoption of the technology. The same kind of thing could have happened with audio CDs.

The other problem is audio storage is inefficient at only 10kB per minute with the 5150 and similar cassette routines. Even placing different programs on the right and left channels still means only a little more than a megabyte could be stored.

Then again, the most common disks being used to publish programs at the time were 5.25" 360K in size. A single audio CD could take the place of three of those. As the industry progressed, file compression was used to stuff more on the same disk. This could have happened on the audio side as well. We got expansion cards to improve everything else in a PC, why not improved cassette ports with faster, more data per second algorithms?

Cassettes are interesting from a historical perspective but for everyday use they suck. So if you are a software developer and 99% of your market has a floppy drive, you are releasing on floppy.
The CD instead of cassette was an interesting concept once the 90s and cheap CD players arrived but mostly would be gimmicky cover discs.

Unless the cassette port was well established as a publishing medium. Even in the early 1990's, ZX Spectrum programs were still being released on cassette. And as mogwaay said:
Also in Europe there was compilation Audio CDs of games and for some computers - Nostalgia Nerd went through some of them a while back, for the ZX Spectrum and Comodore 64 I think

Granted, the Spectrum had started out with only cassettes. By the '90s, however, Spectrums could also have disk drives. The question really seems to be one of pursuing the low end market, which IBM had no reason to bother with when they were raking in cash on the disk-based systems.

Lest I forget, there were two advertised sets of software on cassette in the US. AFAIK, neither was released in cassette form. One was MS's Typing Tutor as seen in 5150 catalogs. The other was Home Computer Magazine which offered the listings on cassette for the PCJr.

This makes me think that the success of the disk-based market was surprising enough to cause the IBM team to focus exclusively on it. Also, they really blew it trying to target the home market with the PCjr. Again seeming to show a mindset geared toward the higher end/business market that was IBM's normal field. The problems with the PCjr were also on the consumer side, expecting a cheaper version of the IBM PC "tank" they already were using at work. Not the cheaper yet lightweight, somewhat incompatible, less indestructible "thing" that appeared on the shelves. (No offense meant to those who love the PCjr. From what I've heard, this was the public opinion of the time.) The Junior's cartridge system never took off and cartridges were a big medium on IBM's home competitors at the time.

On a final note, and getting back more on to the original topic of this thread, one of the real mistakes I think IBM made with the PC cassette port was not integrating it into the disk-based side of the system. Being able to transfer to disks by yourself the programs you previously bought as cheap tape versions would have been a boon for the upgrading consumer. Conversely, transferring disk-based programs to tape (which mogwaay did for PC-Man) on your IBM at work, so that you could use the program you bought at home, would have been a boon to the lower end consumer. This should have been a simple DOS command like COPY and totally automated for the user. Instead, IBM sold everyone two separate computers in the same box and only supported one of them.

I think if this conversation is to continue any further, we should start a new thread, perhaps in a different group.

Basicode had routines that could use the IBM PC cassette port or a parallel to cassette adapter for XTs or ATs to get radio broadcasts of software converted.

This is interesting. I wasn't aware of any cassette option at all for the XT/AT series. Can you post a link to any further info about the adapter? It might be a way for mogwaay to be able to try his PC-Man tape file on a machine he owns. Would it work for his TXjr?

@mogwaay: I hope you haven't minded this digression from your thread. I would like to see further PC Booters converted to tape. My list above would be a great starting point, I think. It's an interesting, if not "really useful" project for seeing what the capabilities of the neglected side of the PC/jr are. (So neglected, for example, that I remember coming across a PC magazine reference that suggested the only use for the cassette port was to make "motor boat" sounds.) It would also be great if someone can confirm this process works on real hardware. After you've done a few of these, I'd think you should be able to program a MAKETAPE command for DOS that does the work for you.
 
I still suspect that IBM only added the cassette and 16K options for marketing. They could advertise a lower "starting at" cost to draw buyers in, just like auto manufacturers. Then when people add the options they really want, they discover the cost is significantly more. But some would purchase anyway. Remember that PC DOS had zero cassette support and couldn't even run in 16K. So if you were buying a 5150 in this configuration, you were paying a lot of money for a computer that couldn't even run IBM's own OS.

Also it makes no sense to distribute software on audio CDs. CDs are already digital. You would just be adding an unnecessary step that makes them slow and inefficient.
 
Basicode and its parallel to cassette adapter: https://github.com/jacgoudsmit/Basicode which includes source code to allow it to run. There was also a mass produced design offered through Dutch public radio and a similar design produced to handle the former Soviet IBM PC compatible cassette formats. The Dutch public radio version includes comments on the range of systems it will work with ranging up to the PS/2 Model 70 and some special case modifications like adding batteries to work with the Amstrad parallel port. Note: a disk drive will be needed to run the software.

Business cassette use: The TRS-80 had a lot of business software available for cassette system during the time before disk controllers became available. I used those as a sort of benchmark for my thought exercise of what IBM would have done had half the world's production of floppy drives vanished. The British scene (especially the Spectrum) had a good selection of cassette applications. Having multiple disk interfaces meant that developers targeted cassette with software that could run on whichever disk the user had. Japanese designs like the Sharp MZ-80 had built in cassettes and software to match. The absolute most absurd use of cassette in business was in the Communist nations where central planning intended on producing 10 computers for every floppy drive. With the oodles of cheap memory available in the late 80s, the MC-85 running CAOS and Wordpro could edit 48K files from cassette. Sadly, the Soviet PC compatibles did not have similarly capable business software on cassette.

CD versus floppy: One other problem for CDs is the cost of producing the master copy for the pressing. What I remember is that in the 80s, it cost many thousands of dollars to do that. The production run has to be massive to spread out that cost. A magazine cover CD would have the volume. The Basicode CD includes an apology about not using CDROM which would have stored every single program ever written for Basicode with ease. But Basicode was from the land of Phillips and probably happy to promote CDs. A floppy disk would be cheaper and store as much and doesn't have the startup costs. After the mid-80s, floppy disks were even cheaper than cassettes. Change was coming and it was digital.

IBM PC cassette port: It was necessary for the development of the PC. The floppy controller wasn't ready until February, 1981 so the first 6 months were spent using programs from cassette to test all the other features of the PC. After that, it could have been dropped but would only cut the final price by a dollar. Having the cassette allowed IBM to advertise an artificially low price and meet contracts that required a cassette port from school districts steering away from minis. The useful unit price with 2 floppy drives and 64K of RAM was about the same as the TRS-80 and Apple II with full memory expansion and 2 floppy drives.

One side note: The IBM PC's comparatively impressive sound capability is done by the same circuitry that did the cassette port sound generation. An IBM PC developed without cassette might have had a very rudimentary beeper. The corollary to that is that the IBM PC might be able to run the cassette port reliably at much higher speeds.
 
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:cautious:

Even compared to the Apple II and TRS-80, I can't say the PC speaker is impressive. Maybe adequate.
The Apple II with machine language assistance matched the PC producing sound in the same way. The TRS-80 required removing the cassette deck to run the sound out the port which is fairly inconvenient. The competing S100 machines tended to have no sound of any type and don't believe the Tarbell cassette card could be tweaked to output meaningful sound. For a business machine in 1981, the IBM PC sound was amazing.
 
Weren't there Apple II sound cards already available when the 5150 was released? And a year later the C64 was released. Adequate for "business" yes, amazing no.
 
IBM PC cassette port: It was necessary for the development of the PC. The floppy controller wasn't ready until February, 1981 so the first 6 months were spent using programs from cassette to test all the other features of the PC..
Didn't they have that "manufacturing test" device mentioned in the BIOS listing, which loaded custom code through the keyboard port during POST?

I can remember at least one commercial IBM PC game (Avalon Hill's Galaxy?) which was sold on disk, but had the option of saving to/loading from cassette. Naturally the game itself was written in BASIC. I suppose they were trying to save you the cost of a blank diskette, back when they still weren't cheap.
 
Weren't there Apple II sound cards already available when the 5150 was released? And a year later the C64 was released. Adequate for "business" yes, amazing no.
There was the Mockingboard which had fairly limited support. I couldn't find an exact date for release but the 1983 pricing was about $100 for just the simple music and $200 to have music and speech which significantly cuts into the price advantage of the Apple II. Which is more useful for a machine: 128K of extra RAM, or a floppy drive, or a sound card that is only supported by a score of programs some of which won't appear until 1988? (Each option cost about $200 in 1983.)
 
There was the Mockingboard which had fairly limited support. I couldn't find an exact date for release but the 1983 pricing was about $100 for just the simple music and $200 to have music and speech which significantly cuts into the price advantage of the Apple II. Which is more useful for a machine: 128K of extra RAM, or a floppy drive, or a sound card that is only supported by a score of programs some of which won't appear until 1988? (Each option cost about $200 in 1983.)
Well that depends if "amazing" sound is a priority. IBM decided it wasn't, so we got the PC speaker.
 
Didn't they have that "manufacturing test" device mentioned in the BIOS listing, which loaded custom code through the keyboard port during POST?

I can remember at least one commercial IBM PC game (Avalon Hill's Galaxy?) which was sold on disk, but had the option of saving to/loading from cassette. Naturally the game itself was written in BASIC. I suppose they were trying to save you the cost of a blank diskette, back when they still weren't cheap.

Nothing I can find explains the details of the manufacturing test though if I understand it correctly, the program will only be 255 bytes long. That short a program won't test the interactive functions in the way that even a simple BASIC program can.

Galaxy was the one. I am not sure why AH bothered to remove the cassette support when they ported the other games over to the PC.

One other program using the cassette port was The Organizer or The Desktop Organizer which was an early PIM ported from the Apple II. It used the cassette port for a copy protection dongle. It was released just after the IBM XT which made for unfortunate timing.
 
Doesn't the red binder "introduction to the IBM PC" that was shipped with all 5150s describe a system with no floppy drives? So it must have been in someone's head back in 1982, along with a TV adapter. (No need to purchase a 5151 or 5153). A 16K-no floppy 5150 "bare unit" (no cards installed) with keyboard was being sold for about $1000 at Computerland--one could buy a Z80 system with monitor and floppies for about that.
The cassette port was mostly useful because it gave you a program-controllable relay.
 
@mogwaay: I hope you haven't minded this digression from your thread. I would like to see further PC Booters converted to tape. My list above would be a great starting point, I think. It's an interesting, if not "really useful" project for seeing what the capabilities of the neglected side of the PC/jr are. (So neglected, for example, that I remember coming across a PC magazine reference that suggested the only use for the cassette port was to make "motor boat" sounds.) It would also be great if someone can confirm this process works on real hardware. After you've done a few of these, I'd think you should be able to program a MAKETAPE command for DOS that does the work for you.
Not at all, I find this discussion really interesting! I don't think I have too much more to add really - I'm no expert in IBM PC history :) I don't think I'll make another tape soon as I've got other projects on the go, this was mostly a technical demonstration that loading a binary game from Cassette BASIC on a PC was possible - no DOS required, just like a Speccy/BBC/Amstrad/C64, etc...

My summation seems to be that there was clearly no appetite at IBM for Cassette tapes so they ditched it ASAP once it had served it's purpose of showing they had launched a 'real' Micro-computer. I'm still a little surprised that none (apart from the ill-fated Advance-86) of the cheap clones tried to run with it - esp. the Tandy 1000s, which I think did well in the home market, or the Amstrads in the EU, but I guess by that time IBM PC Compatible = Offie Computer = Disk Based Computer. That also sums up a bit of my confusion as a kid that the PC was a Microcomputer as a Microcomputer to me didn't have Disks (mainly Hard, but Floppy was also fancy), a DOS, expansion slots, monitors, etc...
 
Basicode and its parallel to cassette adapter: https://github.com/jacgoudsmit/Basicode which includes source code to allow it to run.

Thanks for that! It looks like an interesting addition for this thread.

@mogwaay: I hope you haven't minded this digression from your thread.
Not at all, I find this discussion really interesting! I don't think I have too much more to add really - I'm no expert in IBM PC history :)

Great, then I have a little more about this:

A 16K cassette only 5150 would cost more and be less effective than a 16K cassette only TRS-80 Model III. 8086 code would be slightly bigger and losing 1k to interrupts doesn't leave a lot of memory even for a minimal word processor like Electric Pencil. IBM also charged a lot of money for those empty slots and bays. Now, a 64K+ IBM PC with cassette could do more than the Z-80 counterparts but for business, the upgrade to disks was a no brainer. 64K takes about 6 minutes to load off cassette. For a hypothetical 128k text editing system, that would mean 6 minutes loading the text editor, 6 minutes loading the file, 6 minutes saving the file for lunch, 6 more minutes saving the file before leaving for the day for a total of 2 hours wasted each week. Not difficult to discover that floppy disks will quickly save money.

Business cassette use: The TRS-80 had a lot of business software available for cassette system during the time before disk controllers became available. I used those as a sort of benchmark for my thought exercise of what IBM would have done had half the world's production of floppy drives vanished. The British scene (especially the Spectrum) had a good selection of cassette applications. Having multiple disk interfaces meant that developers targeted cassette with software that could run on whichever disk the user had. Japanese designs like the Sharp MZ-80 had built in cassettes and software to match. The absolute most absurd use of cassette in business was in the Communist nations where central planning intended on producing 10 computers for every floppy drive. With the oodles of cheap memory available in the late 80s, the MC-85 running CAOS and Wordpro could edit 48K files from cassette. Sadly, the Soviet PC compatibles did not have similarly capable business software on cassette.

Okay, now I'm confused. Granted most computers that had a cassette port had business software available on cassette. I also agree that a cassette-based 64K IBM PC was more powerful for business than a cassette-based 64K Z-80 competitor, like the TRS-80. But, since the TRS-80 had an optional floppy disk system too, why do you think business program cassettes made sense for the TRS-80 vs. IBM PC? Why didn't the 2 hours wasted each week cause a mass switch to floppy disks on the TRS-80? Or have I misunderstood your point regarding TRS-80 business cassettes?

IBM PC cassette port: It was necessary for the development of the PC. The floppy controller wasn't ready until February, 1981 so the first 6 months were spent using programs from cassette to test all the other features of the PC. After that, it could have been dropped but would only cut the final price by a dollar. Having the cassette allowed IBM to advertise an artificially low price and meet contracts that required a cassette port from school districts steering away from minis. The useful unit price with 2 floppy drives and 64K of RAM was about the same as the TRS-80 and Apple II with full memory expansion and 2 floppy drives.

Well, those are some things I wasn't aware of. I assume when you say "cut the price by a dollar" that you mean they would only drop the DIN connector from the finished product. It makes more sense that the PC would have a cassette port if they couldn't use/weren't sure they'd have a floppy drive by launch time. The school districts requiring a cassette port would also reinforce the need to keep it. That clears up that point well.

But, I'm still skeptical that these were the only reasons. Even adding the point about marketing at a low price doesn't explain why the PCjr, launched in 1983 -- 2 years after the floppy controller was ready -- had a casette port. This computer was supposed to be for the home and had a superior sound system. Did it have a cassette port for the same reasons? It seems unlikely to me, but I don't know either.

One side note: The IBM PC's comparatively impressive sound capability is done by the same circuitry that did the cassette port sound generation. An IBM PC developed without cassette might have had a very rudimentary beeper. The corollary to that is that the IBM PC might be able to run the cassette port reliably at much higher speeds.

I'm not too familiar with the hardware of the PCjr, so I'm wondering if its sound circuitry was also used to generate the cassette port output. If so, then maybe it had a cassette port for the same reasons. But, then again, why was the port removed from the PC XT since it had the same sound circuitry as the PC? My guess is that the PCjr continued to have a cassette port because it was for the home market where cassette usage was still common and the PC XT had it removed because it was intended for the business market where cassette storage was quickly becoming obsolete.

Regardless of which one of us is right, we all know that floppies and hard disks where eventually going to win, even if IBM had embraced the cassette port. It was only a matter of time before all cassette based machines still being produced would phase out cassette storage.

In case anyone hasn't come across it before, further info on the cassette port, especially as it was available on the PCjr, comes from mbbrutman on his website:

https://www.brutman.com/Cassette_Waveforms/Cassette_Waveforms.html

On that page he says "In reality nobody probably ever used the cassette port on an IBM PC - it is just too slow and unreliable. Anybody who was forced to use a cassette on any machine would immediately buy a diskette drive, no matter what the cost."
 
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