Cratedigging

[DrG]

RE: Cassette tapes.

The KIM-1 had a very simple, and very utilitarian, cassette interface:

APPENDIX E

AUDIO TAPE FORMAT


Data is stored out onto your audio cassette recorder in a specific
format designed to insure an error free recovery. In the unlikely event
that a playback error does occur, several "ERROR DETECTION" methods are
incorporated to warn you of this condition.

Data is transmitted to the tape recorder in the form of serial
"ASCII" encoded characters (seven data bits plus Parity bit). Data
retrieved from the memory is converted into this form by separating each
byte into two half bytes. The half bytes are then converted into their
ASCII equivalents.

/----/

Each transmitted bit begins with a 3700 hertz tone and ends with
a 2400 hertz tone. "Ones" have the high to low frequency transition
at one-third of the bit period. "Zeros" have the transition at two-
thirds of the period. During playback the 565 phase locked loop locks
to, and tracks these two frequencies producing (through the 311
comparator) a logic "1" pulse of one-third the bit period for a "One".
A pulse two thirds the bit period is likewise produced for a "Zero".
Your microcomputer uses a software controlled algorithm for converting
this signal into eight bit data words.

The frequency shift keyed phase lock loop method of data recovery
is relatively insensitive to amplitude and phase variations. The "FREE
RUNNING" frequency of the phase lock loop has been adjusted at the factory
to a frequency half way between the two data frequencies (called the Center
Frequency). This adjustment is accomplished by strapping Pin A-P (Audio
Out High) to Pin A-L (Audio In). A program starting at address 1A6B HEX
provides the center frequency reference that allows the loop to be
adjusted by potentiometer VR1. Pin E-X (PLL TEST) is monitored with a
voltmeter while the pot is rotated until the voltmeter reading is at the
transition point between a logical "1" (+5v) and "0" (GND).

Because they used a ratio of frequencies to represent 0 and 1, it was not long before someone (Jim Butterfield) figured out that you could shorten the burst length but keep the ratio, and speed up the loading time.

 

[dr pepper]

Yes 1982 I think.
It had an os unlike the tangerine.
I also might still have somewhere the college's training machine which has a 8080 on it, it only has 5mm leds for display.
Such things are gone, probably a good thing, I wouldnt like to write a lora system on one of them.

 

[Nigel Goodwin]

RE: Cassette tapes.

The KIM-1 had a very simple, and very utilitarian, cassette interface:


Because they used a ratio of frequencies to represent 0 and 1, it was not long before someone (Jim Butterfield) figured out that you could shorten the burst length but keep the ratio, and speed up the loading time.

View attachment 121235

Well the Tangerine Microtan 65 came out in 1979, and the tape interface on the expansion board and the expanded ROM routines used the CUT's standard, which was 300baud if I remember correctly?, this allowed maximum compatibility across different cassette recorders. However, the first thing you did was type in a faster load and save routine, which you saved at the CUT's speed - then you simply loaded that first, and continued to use the faster routines.

Any programs you bought came at CUT's standard for maximum compatibility, however one I bought came at the high speed, because it was such a huge program (something like 28K?) - this was a text adventure, written entirely in machine code. As such I had great difficulty loading it, eventually I used one channel of my Sony Stereo Cassette Deck, and of course immediately saved it back to my normal little cassette recorder.

They were different times, lot's of fun

Must admit, I always liked the 6502 - and the peripheral chips seemed much superior to the 8080/Z80 ones.

 

[DrG]

The cassette tape on the TRS-80 was ummm challenging...and very sensitive to volume. Soon, devices came out, like this one:

They were little more than a 7414 cleaner-upper, but they did improve operation significantly.

BTW: I have used a number of tape back up units and all of them, in my limited experience, pretty much sucked whether they were older (like ones for the PDP 11/73) or newer ones for the PCs. There was always the fear, often realized, that that back up tape was going to fail when you need it most.

Now, the low price of multi TB mobile drives represent a notable improvement.

 

[Nigel Goodwin]

BTW: I have used a number of tape back up units and all of them, in my limited experience, pretty much sucked whether they were older (like ones for the PDP 11/73) or newer ones for the PCs. There was always the fear, often realized, that that back up tape was going to fail when you need it most.

My younger brother used to work for a bank, and at various times was involved in the computer side, including tape backups - I was horrified at the reliability and error rates of the tape units.

Now all that stupid stuff is long since gone.

 

[dr pepper]

In 20 or 30 years time, those of us still alive will no doubt be saying todays stuff is stupid.

 

[gophert]

My younger brother used to work for a bank, and at various times was involved in the computer side, including tape backups - I was horrified at the reliability and error rates of the tape units.

Now all that stupid stuff is long since gone.

Not long gone...
I just stumbled upon a used robotic arm at an industrial flea market. The arm was part of a tape backup system used by the State of New York. The owner said there was a library of more than 1000 tapes that the arm selected and placed into one of 64 tape backup drives.

He didn't have all the details of how the backup software worked, he was just hired to remove the arm and safety cage around the arm. It had worn out over the years and too much slop and poor reliability in the tape system caused the state to obsolete the system.

 

[dr pepper]

Back in the eraly 2000's I maintained a CNC internal mill, it had pushpin programming, some pins were diodes, some shorts some resistors, it all went to china but I wouldnt be surprised if its still running, the next model up had a tape drive, the tape wasnt on a reel, some weird big box with the tape laying in the bottom.

 

[KeepItSimpleStupid]

PDP-8, PDP-11, 6800
The Intel and Z80 assember and even CP/M really turned me off because I'd seen and used better tools.
How about the COSMAC 1802. No Gosub statement, but any register could become the program counter.
The first thing I wrote was a way to do GoSub. I hand assembled this code.
I did buy an Amiga.
One day I got bored, so I used Microsoft Word on a MAC to write programs in PostScript to send to a printer - Laserwriter NTx

 

[DrG]

How about the COSMAC 1802. No Gosub statement, but any register could become the program counter.
The first thing I wrote was a way to do GoSub. I hand assembled this code.

I did have some interest in that RCA chip. It made the rounds in the Computer and Electronic magazines and seemed "different", but, as I remember it, nobody was claiming it was as fast or better than the Z-80 or 6502.

You can get new ones for a couple of bucks on the bay. 14MhZ 65c02s are a little more expensive but are also readily available. I have spent some time looking at the many newer builds for "antique" micros...it's interesting, but with then length of my project list, I quickly stop myself from going too far.

... write programs in PostScript to send to a printer - Laserwriter NTx

In their day, HP printers were rock solid tanks and they had the best plotters around for the price. Now days, one looks at the price of toner as the determining factor *sigh*.

 

[picbits]

I started off in around 1981 on an RML380Z - interesting days. I've currently got a couple of Promate II programmers, Picstart Plus (white and black), a handful of Pickit 2 and 3s and somewhere my old P16PRO (or something) homebuilt parallel port programmer for PIC controllers.

 

[Nigel Goodwin]

How about the COSMAC 1802. No Gosub statement, but any register could become the program counter.

It was 'different' because it was a CMOS processor, and thus far lower power consumption than others - as I recall that was one of the reasons it was used by NASA, and also because you could easily reprogram it from earth.

 

[KeepItSimpleStupid]

In their day, HP printers were rock solid tanks and they had the best plotters around for the price. Now days, one looks at the price of toner as the determining factor *sigh*.

The Laserwriter Ntx was an Apple printer

The Laserjet 4m and 4m+ was a really nice printer. Work bought 4 or 5 of these. https://en.wikipedia.org/wiki/HP_LaserJet_4`

At home I have a P2015dn printer (wired network, duplex). HP took the firmware off their website. I had to bake the formatter board in an oven. It has like 30K pages on it. It really doesn't like to be single sheet fed. That area is a little flimsy. If I were doing lots of single sheet feeds, I'd put a magnetic catch on the door if I could. I do have a spare. It can have a straight paper path which is very useful.

One roller cover like to dislodge every once in a while. I've replaced a few pick-up rollers once. I need to store unused Staples paper somewhere other than the basement where the printer is.

Quality has gone way down.

 

[dr pepper]

Nige wasnt/is there an arduino on the spacestation that you can upload code to & run it?
Probably wait all day then get 2 seconds run time, but interesting.

 

[DrG]

The Laserwriter Ntx was an Apple printer

The Laserjet 4m and 4m+ was a really nice printer. Work bought 4 or 5 of these. https://en.wikipedia.org/wiki/HP_LaserJet_4`

At home I have a P2015dn printer (wired network, duplex). HP took the firmware off their website. I had to bake the formatter board in an oven. It has like 30K

My mistake. Yes on the HP Laserjets and also the 4D. They could heat a small room but they worked and they worked well and for a lng time. Yes, quality simply dissolved as they competed in the el cheapo market. I personally have a Brother and the thing had dome well by me.

Edit: and their monster color printers cost too much and always screwed up. People thought they were so cool until the realities hit them.

 

[DrG]

Nige wasnt/is there an arduino on the spacestation that you can upload code to & run it?
Probably wait all day then get 2 seconds run time, but interesting.

Ardusat?

 

[KeepItSimpleStupid]

DrG I also have a HP Laserjet Pro M477fdw color laser, but it isn;;t even out of the box. It;s been that way for quite a while. It tells you how busy I've been.

I have a PT-1400 manual Brother label printer. I was surprised how easy it was to get parts a service manual The cutter requires finese to use it. Again, got parts, got manual, but not fixed.

I obtained an Epson MFC Inkjet service manual and that manual blew me away, but Epson isn' t friendly. You need a service tool progam.
manuals are mostly unobtainium, but parts are easy. The scanner image sensor broke during a flood. I have the parts to fix. One part you have to use a new one everytime the printer is opened.

Epson wasn't responsive for a really simple modification to their scanning software except, it was a good idea. All I wanted is a suffix for the filename input.
e.g. P#####S. The numbers auto-increment.

The ADF (auto document feeder) only scans one side so you get P001, P002 etc. for each page.

Now, let's scan the other side. So, you get P001, P002 etc.

What i want is P001A, P001B, P002A ... and have Acrobat put them all together in one document.

The scanning program wasn;t smart when fed documents printed in part landscape and part portrait.

That's enough to not buy Epson.

Apple pissed me off too. I could not get past the gatekeeper and they think their stuff is flawless. On the iBook, i found that if you sent an email with ATH$ from a land-line modem, it would hang up EVERY time and they would not listen to me. 6 monhs later they fixed it.
They forgot the 1 second silence band.

Work bought an instrument from one of the following companies: Fluke, HP (Keysight), Keithley. I told them that there was a 200 V spike on the inputs that were destroying our devices when the instrument switched ranges. They were really skeptical. They agreed and immediately sent us a temporary fix that disabled other instrument functions and then engineered a real fix and did it for free.

Another company which we had a really good relationship with, a power supply died. I do my quick troubleshootig and determine that a rectifier died. No big deal except the part was rated for 10A and the device was rated for more that 40 Amps. OOPs. They offered to fix which required a new transformer as well when we sent the other part for a month re-furbish. They had to engineer that fix too. it was unclear if they knew about it.

Knowing what was wrong gave me an edge.

Recently, I bought an audio harness that switched, the front and rear speakers. The ebay seller nor the manufacturer offered no fix.
I can pull and rearrange the pins. I have the tool.

I had to re-wire a high purity vapor drier because the wire guage wasn;t large enough. I don;t think I contacted the manufacturer/

We had problems with a scientific program that would not run on a particular Macintosh without intermittant crashes. Again,they were skeptical, but they sent us a special debug version of their program and fixed it.

 

[dr pepper]

Docg ardusat looks cool.
Excellent idea for shoolkids to get a buzz out of.

 

[DrG]

. I've currently got a couple of Promate II programmers, Picstart Plus (white and black), a handful of Pickit 2 and 3s and somewhere my old P16PRO (or something) homebuilt parallel port programmer for PIC controllers.

Do you use them? If not, why do you keep them? I ask myself that question and wonder how others would answer.

 

[Pommie]

Do you use them? If not, why do you keep them? I ask myself that question and wonder how others would answer.

I have more junk than I care to admit. It'll come in useful one day. And if I throw it out, I'll need it the very next day.

Mike.