Yes, but not necessarily very old and very expensive. If you can find a "real" speaker you could use something relatively modern and available I believe.
konc said:
Yeah, but relatively modern would also mean faster, which removes the challenge of doing this for the oldest and slowest machines.
Thanks! That's an interesting example of how people went above and beyond to get a quality sound while using minimal resources.Even with a mainboard that has a small piezo speaker, we're talking about PWM here - the speaker output is usually open collector, and the speaker itself connected between +5V and /SPK. A NOT gate such as the 7404, 1 signal NPN with its emitter grounded, and a base resistor of around 100 ohms to the output of the NOT gate, that should be enough for him to connect regular 8-ohm magnetic speaker between the collector and say +12V of the PSU to get real loud sound. No investments in expensive technology needed.
As far as the 4.77MHz XT goes, the nicest PC speaker "digitized sound" I have heard from a DOS application, was from a French game called Space Racer. It plays its theme tune that's almost a minute long from two unsigned 8-bit mono samples, MUSIC0.SPL and MUSIC1.SPL (each 42K and 55K in size, respectively), sampled at around 10 kilohertz, by loading them to memory at once, and then playing predefined parts (i.e. not the whole sound file at once). There's some whine present even on the real hardware, but it's far from being ear-piercing, and a regular ole PC/XT is enough. Their executable (SPACE.EXE) is not packed or obfuscated so you could have a look at their timer ISR. You won't get more "Hi-Fi" than this, unless you go via the route of D/A converters, reinventing the sound card in the process.
Yeah, but relatively modern would also mean faster, which removes the challenge of doing this for the oldest and slowest machines.
I'm not too concerned about price, but space is my problem. I don't have much space in the apartment or on my table for one more machine
I gave it my try this evening: made an app to convert the 8-bit PCM into 1-bit PWM, shortening the datastream size eight times, and instead of programming the speaker channel 2 frequency in the timer ISR I just flip its enable flag accordingly. This yields loud sound, comparable with regular beeps, and having zero whine at a sampling rate of 14 kHz still usable on the stock 4.77MHz 8088. But it's not really usable for "music" unlike some wacky sound effects, because of the resulting distortion. Here's Bill Hanna's famous Tom and Jerry scream played on the PCjr... I think it's fitting.
Haha, this is hilarious!I gave it my try this evening: made an app to convert the 8-bit PCM into 1-bit PWM, shortening the datastream size eight times, and instead of programming the speaker channel 2 frequency in the timer ISR I just flip its enable flag accordingly. This yields loud sound, comparable with regular beeps, and having zero whine at a sampling rate of 14 kHz still usable on the stock 4.77MHz 8088. But it's not really usable for "music" unlike some wacky sound effects, because of the resulting distortion. Here's Bill Hanna's famous Tom and Jerry scream played on the PCjr... I think it's fitting.
The program exits on the ESC key only new_int8:
lodsb
or al,al
jne not_end
mov si,offset sample
lodsb
not_end:
out 42h,al
mov al,20h
out 20h,al
iretwait_for_esc:
or bl,bl
je wait_for_esc
Wow! It is really loud and even sounds pretty clear on the recording!
Nice! I'll check this. Thanks!
Still, if it was intelligible by comparative standards, novelty and small files meant that it was worthwhile...until better techniques (better hardware) came around. The same data could, and was, used, in C64 and apple ii. You just slammed it out the speaker bit - literal bit banging.
Not sure I am following your reference "He's actually doing eight bits here" - you realize the "he" in my post / source code example is me back in the late 80s - right?