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101090 discussions

Audio Cassette formats, was: RE: Recent Finds & Thoughts

by allisonp＠world.std.com

< > Yeah 44100Hz/16/stereo eats up space perdy quick, which is why < > I'd like to try or hear from someone whose tried the various FYI, protable casette recorders 3db point is 11-14KHz for the better ones and they typical ones used 9.5-12.5KHz is more realistic. Sampling above 20Khz is wasting bandwidth and recording time. Even the fastest audio formats (sudding and TARBEL187bytes/sec) had bandwidths below 5KHz. Allison

27 years, 9 months

Front Panel Theory

by cmcmanis＠freegate.com

Not trying to be a snob here, but true "Front Panel Theory" can only be practiced on a computer where the 'innards' are exposed. Most microprocessors are too integrated to support a "real" front panel. This is one of the reason they died out fairly quickly in the micro world but lived for quite a while in the mini-world. Basically an ideal front panel contains enough switches to set any memory address, load any register, and start, stop, and single step the CPU, and enough lights to monitor both system state and the current address. Many older panels let you look at several things simultaneously but later ones like the PDP-11 and PDP-8 panels used selector switches to multiplex the lights and reduce cost. --Chuck At 06:03 PM 11/25/98 -0600, you wrote: >This might be a bit of an odd question, but can anyone point me in the >right direction to find info on theory of operation of a front panel? I >have a z80 based computer which I built a few years ago (wire-wrapped) >which uses an eprom for program storage. I would like to add a front >panel (switches and lights) to it to get better aquainted with the old way >of doing things. Unfortunatly, my knowledge of microprocessor-based >systems post-dates the era of front panels. The eventual goal is to build >a hands-on display to show how systems were bootstrapped. (without >letting people abuse a 'priceless' altair or imsai) > >Thanks, >srw > >

27 years, 9 months

Audio Cassette formats, was: RE: Recent Finds & Thoughts

by cswiger＠wilma.widomaker.com

Mark[SMTP:mark_k@iname.com] sez: >I have many old computer cassettes, and have been thinking of >recording them onto a computer in order to preserve their >contents. The signal from computer tapes oscillates between >two levels, right? This being the case, it should be possible >to record them using 1-bit sampling. Perhaps record with 8- or >16-bitsampling and then convert down to single bit. > >Are there any programs to do this conversion? I imagine the >equivalent of a Schmitt trigger (in software) would work. What >about playing back a 1-bit audio signal? Are there any standard >audio file formats that can be used to store 1-bit data? Well, there were/are many formats to put data onto tape, the only one I'm famalier with is as you said a FSK or frequency shift keying, using one tone for a mark or '1' and another for a space or '0'. See http://www.threedee.com/jcm/audio/index.html for some work in this area. >Actually recording tapes to audio CDs is quite wasteful since >you can only get 70 minutes or so on a CD (an issue if you have Yeah 44100Hz/16/stereo eats up space perdy quick, which is why I'd like to try or hear from someone whose tried the various levels of RealAudio or open std. MP3 compression - using those one can get hundreds of hours of 'not bad' audio on a single CD. (e.g., one 30 minute radio program = about 5Mb of MP3). Chuck cswiger(a)widomaker.com P.S. Nerds 2.0.1 on PBS tonight

27 years, 9 months

Dismantling an AT keyboard entirely

by Philip.Belben＠pgen.com

>> The only time that I would think the clicking would give someone a headache >> would be if they were locked in a sound-proof round all-white room with no >> windows, and dome ceiling, but then again, that's just my opinion. > > Try teaching an operation or programming class in a room full of > thosed damned clicky keyboards. You'll fire up the chainsaw before > an hour is out to drown out the racket. A lot of people don't like key clicks. I do. When I worked at IBM I received a lot of dirty looks for typing on a 3279 terminal, in an open plan office, without turning off the key clicker. Now that really was loud! Philip.

27 years, 9 months

Front Panel Theory

by scott＠saskatoon.com

This might be a bit of an odd question, but can anyone point me in the right direction to find info on theory of operation of a front panel? I have a z80 based computer which I built a few years ago (wire-wrapped) which uses an eprom for program storage. I would like to add a front panel (switches and lights) to it to get better aquainted with the old way of doing things. Unfortunatly, my knowledge of microprocessor-based systems post-dates the era of front panels. The eventual goal is to build a hands-on display to show how systems were bootstrapped. (without letting people abuse a 'priceless' altair or imsai) Thanks, srw

27 years, 9 months

Old 386 and 486 pc's

by manney＠lrbcg.com

>One was an Everex with a mondo-scarce RLL drive. . . Which one? RLL's aren't _all_ that scarce. manney

27 years, 9 months

Call for final Elf99 design input

by allisonp＠world.std.com

< This means no CHIP-8. :-( No it means CHIP-8 graphics are out. Chip-8 can be hacked for other devices like terminal io. Also the resolution of the VIP was slow low that a matrix of leds might be doable as a display. as a possibel subtitute. Allison

27 years, 9 months

more interesting finds!

by rigdonj＠intellistar.net

I went to a scrap place yesterday and found a couple of interesting items. One is a 16K core memory board for a Data General Nova. Huge sucker! It's marked "DATA GENERAL CORP DGC NOVA 800 16K MEMORY STACK copyright 1973". Anyone need this or should I just hang it on the wall to admire? I also found several odd looking boxs that are labled as HDS ViewStation. they're made by a company called Human Designed Systems. They're about 2" tall and 12" square. They have connectors for all the following; thick and thin ethernet, twisted pair, sun keyboard, standard PC keyboard, RJ serial port, DB-25 serial, DB-25 parallel, PS-2 mouse and standard VGA video. Does anyone know what these are or why they have so many ports? Joe

27 years, 9 months

Call for final Elf99 design input

by yakowenk＠cs.unc.edu

On Tue, 24 Nov 1998, Ethan Dicks <erd(a)infinet.com> wrote: ] I am cranking along with the capture of the Elf99 design (on OrCAD for DOS, ] a 10-year-old program, no less). I wanted to throw out what I have ] descided on and ask for suggestions on what is not set in stone. ] ... I didn't speak up before, but I'm sitting on the "interested" side of the fence. As for my personal preferences, modern chips are fine, if they are cheap, easy to use, readily available, and relatively standard (so they are likely to remain available for a while yet). I never had an Elf of any sort, so I don't have any attachment to any particular aspect of that. So to me, being 1802-based and being cheap/easy would be the big attractions. If I could populate the entire board for under $20, that would probably be enough to pull me off the fence entirely. Cheers, Bill.

27 years, 9 months

Dismantling an AT keyboard entirely

by allisonp＠world.std.com

< The keyboard should now work. Mine does -- I typed this on it. You forgot one step in the disassembly... NOTE where each key is removed from. Otherwise I typed this on it. becomes Y riowd kida no wq, ;) Allison

27 years, 9 months

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