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Mini version of the OSI-300 trainer
Posted: Wed Dec 16, 2015 12:58 am
by ChuckT
Mini version of the OSI-300 trainer
The OSI Model 300 Computer Trainer was advertised by Ohio Scientific Instruments in 1976 as a computer designed to introduce individuals to computers and teach them the basics of programming the MOS 6502 processor. The original trainer consists of a MOS 6502 processor, 6810 128 byte static RAM, one bit output latch, switches for entering data, and LEDs for reading the values of RAM.
The trainer was intended as a starter for individuals before moving on to their more advanced Model 400 Superboard system.
I first encountered one of these at VCFE 9.1 in 2014, and was intrigued by the simplicity of the design. I was particularly interested in the operation, and wanted to learn how the switches and LEDs were interfaced to perform the data read/write operations.
I did a google search of 6502.org and did not find anything on this topic so I'm sorry if I duplicated anything.
Re: Mini version of the OSI-300 trainer
Posted: Wed Dec 16, 2015 1:33 am
by BigEd
LEDs and switches - love it!
The original is bigger but somehow looks simpler, as seen on Hans Otten's site:
Re: Mini version of the OSI-300 trainer
Posted: Wed Dec 16, 2015 1:59 am
by Dr Jefyll
There's a thread (including a schematic) on anycpu.org
here.
Re: Mini version of the OSI-300 trainer
Posted: Tue Apr 05, 2016 4:43 pm
by BigEd
Re: Mini version of the OSI-300 trainer
Posted: Wed Apr 06, 2016 5:45 am
by barrym95838
... The original is bigger but somehow looks simpler ...
It looks like the original had only 128 bytes of address space, while the updated version supports up to 4KB.
Mike B.
Re: Mini version of the OSI-300 trainer
Posted: Wed Apr 06, 2016 7:48 am
by BigEd
Imagine what you could do with 4k!
Re: Mini version of the OSI-300 trainer
Posted: Wed Apr 06, 2016 8:42 am
by barrym95838
Imagine what you could do with 4k!
Get blistered fingertips from hand-jamming a few dozen machine instructions to calculate and display (on four LEDs) the 3141st digit of pi, only to have it all lost to a momentary power glitch?
Mike B.
Re: Mini version of the OSI-300 trainer
Posted: Wed Apr 06, 2016 9:40 am
by BigEd
We must suffer for our art. I'd certainly be tempted to toggle in not too much more than a loader, but that presumes some kind of peripheral to load from - there is none here. A pi program might only be a hundred bytes - most of the memory would be used for data. I accept the challenge!
Re: Mini version of the OSI-300 trainer
Posted: Sun Feb 02, 2020 4:27 pm
by BigEd
There's a recent video showing off the original OSI-300 - there's also an overview of Ohio Scientific's rise and fall.
Toggling action from the 9 min mark:
https://www.youtube.com/watch?v=vww6XbDc2pY
Re: Mini version of the OSI-300 trainer
Posted: Mon Feb 03, 2020 2:08 am
by BillO
At a quick glance the OSI-300 had some ... unique ... approaches to things ...
- Data bus was assumed to be high if left floating
- Writes to memory were not qualified with Phi-2 (in this case fair enough, but not a great template for the student of the 6502)
- No de-bounce on the reset - must have produced some interesting results from time to time
- that clock circuit
- No de-bounce on the NMI - wouldn't this confuse the interrupt handling in the CPU from time to time?
Talk abut being built down to a price.
However the tutorial in the manual was pretty good.