A Cassette Recorder Question

[per]

Does anyone know if it is possible to hook up a cassette recorder (that will work with the ROM BASIC) to an XT?

The PC's have a plug for cassette recorders, but the XT has not. I think there is a driver for cassette I/O in the XT BIOS, but i have no idea if there is any hardware adapter on the motherboard where only the DIN plug is missing.

[Great Hierophant]

Nope, not feasible. The driver in the XT BIOS does not contain full routines, only a small amount of code for compatibility's sake. Then you need to create an adapter in hardware.

[per]

ok.
What do the cassette drivers in the XT BIOS actually do?
*and*
Where can I find thecnical info about the cassette storage thechnique used by the 5150 PC?

[mbbrutman]

Find the technical reference manual and read it? The parts of the BIOS that handle cassette IO are listed in x86 assembly with comments.

[mikey99]

Did the early versions of the 5150 Guide to Operations include
cassette tapes ? I recall seeing a picture somewhere with the
binder open and tapes inside.

Was this just a cassette version of the Diagnostics diskette ?

[mbbrutman]

There is a cassette version of Diagnostics - I have it. I don't think that there was any other IBM labeled software on cassette.

[Great Hierophant]

There is a cassette version of Diagnostics - I have it. I don't think that there was any other IBM labeled software on cassette.

No Cassette BASIC demos? Did the PCjr. come with any cassettes? Do you know of any non-IBM but still PC-compatible software that came on cassettes?

It is interesting that IBM had a cassette interface and supplied a cassette version of Diagnostics but not the DIN-to-audiocable.

[per]

Find the technical reference manual and read it? The parts of the BIOS that handle cassette IO are listed in x86 assembly with comments.

All I found was a statement for the cassette I/O in the vector table at line 5760:

FF0D 59F8 5760 DW CASSETTE_IO ; INTERRUPT 15H(FORMER CASSETTE IO)

There is no "OFFSET" in fornt of "CASETTE_IO" so that piece of code isn't listed in the listings.

There is a cassette version of Diagnostics - I have it. I don't think that there was any other IBM labeled software on cassette.

Is it possible to make raw images of cassettes the same way as with floppies?

[mbbrutman]

My PC Tech Ref has a small section on Int 15h, including how the reading and writing to the cassette is done. The format of the block on tape is even shown. The BIOS listings for the routines are there.

The XT Tech Ref has a smaller section. ;-0 It looks like they just return 'Bad Command' when you call them. Definitely not implemented.

If I were to make an image of the casette I would do it two ways:


Make a high quality WAV or MP3 of the casette itself. This can be played back through the adapter.
Write a program to read the raw blocks of data into memory, and then save them as raw data to a diskette file. This would be for analyzing the code/data that was stored. You should use the BIOS functions to do this. A PC or a PCjr would be required for this.

[mbbrutman]

No Cassette BASIC demos? Did the PCjr. come with any cassettes? Do you know of any non-IBM but still PC-compatible software that came on cassettes?

It is interesting that IBM had a cassette interface and supplied a cassette version of Diagnostics but not the DIN-to-audiocable.

On a PC there is nothing on cassette from IBM except for the diagnostics, and I'm sure that was even done grudgingly. I suspect that nobody in IBM ever thought they would sell a machine without a diskette drive. ;-)

I don't know of 3rd party software on cassette either. It would be a hard sell, unless it came bundled with it's own cable.

The PCjr is an entirely different animal. On the low end it might have been seen as competition for a C64 or other cassette based machine. (That's a stretch.) IBM shipped diagnostics in the ROM of the machine, so that eliminated the need to ship a diagnostics cassette. The 'Keyboard Adventure' program can be counted as a demo, and it is in ROM too.

[per]

My PC Tech Ref has a small section on Int 15h, including how the reading and writing to the cassette is done. The format of the block on tape is even shown. The BIOS listings for the routines are there.

The XT Tech Ref has a smaller section. ;-0 It looks like they just return 'Bad Command' when you call them. Definitely not implemented.



What lines in the listings do you find the code at?

[IBMMuseum]

Does anyone know if it is possible to hook up a cassette recorder (that will work with the ROM BASIC) to an XT?

The PC's have a plug for cassette recorders, but the XT has not. I think there is a driver for cassette I/O in the XT BIOS, but i have no idea if there is any hardware adapter on the motherboard where only the DIN plug is missing.

Lewis Eggebrecht (who has a book I will refer to), the IBM PC design team leader, was rumored to have told Bill Gates (when there was an objection to putting such an underused, as history bore out, cassette port on the PC) [paraphrased] "Just put 35 cents of software to support 35 cents of hardware on the motherboard!". His book, [I]Interfacing to the IBM PC, covers from the PCs up to the early PS/2s. Although not really for hooking up the intended cassette drive, he does show how to modify the cassette port for other hardware applications.

[Great Hierophant]

I think we need someone to record a wave file of the diagnostic cassette playing.