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Microcomputer History
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=93728&th=23133#msg_93728
We talk about tube radios here on AudioRoundTable.com from time to time. Those are definitely vintage pieces of electronics history. But it occurs to me that early microprocessors and microcomputers are too. And since I still have a lot of those eight-bit microcomputers and chips from the 1970s and 1980s, I decided it might be worthwhile to do write-ups on some of them.
So I started out with the Synertek Systems Sym-1. Click the link if you're interested in the early years of microprocessors:
]]>Wayne Parham2021-05-11T21:03:08-00:00Re: Microcomputer History
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=93729&th=23133#msg_93729
Rusty2021-05-11T22:01:36-00:00Re: Microcomputer History
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=93730&th=23133#msg_93730
Well, yes and yes. On some of the most primitive computers, the code is entered one character (or half-character 'nibble') at a time and, yes, it's incredibly tedious. Which was one of the main early goals or programmers in the early days - to develop languages and operating systems that made programming less tedious.
When you enter code that way, it's called machine code, binary or object code. You are talking directly in the computer's language. You might tell the computer to get the contents of a memory location, load into a temporary place called a register, test the contents (like for equality, less than or greater than) and jump somewhere else in the program if the condition was met. Or maybe you'd load contents from memory, add to contents or another memory and store somewhere else.
Each instruction is one-byte code (in a machine like these), so for example, in the 6502 microprocessor, the load instruction is decimal 169 or hexadecimal A9. Microcomputer guys think in hexadecimal. Lots of minicomputer guys think in octal and that same load instruction is 251 in octal. So to program in machine code, you hand-enter a bunch of numbers in sequence. That's your program.
Next level up would be assembly language. In that case, you don't have to know the number of each opcode. You can call it by name, or actually by a "shorthand" abbreviation we call a mnemonic. That A9 load code I just described is called LDA in assembly language, the mnemonic for Load Accumulator. You can also label memory locations instead of calling them out by numbers. So it's one level of abstraction above machine code, not much above, just barely.
Then above that would be languages like BASIC or C. Those are more "human-readable" and require an interpreter or compiler to translate the program into machine code for the computer to be able to act upon.
]]>Wayne Parham2021-05-11T22:19:49-00:00Re: Microcomputer History
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=93766&th=23133#msg_93766
]]>gofar992021-05-14T01:39:08-00:00Re: Microcomputer History
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=96013&th=23133#msg_96013
I love those old multi-platter disk drives. And you're right that they were the size of washing machines. Shook like a washing machine too during rapid disk seek operations. They usually had a large linear motor that moved the heads, and by large, I mean 100 pounds or so. Enough force they could break your arm if it went into emergency retract while you were aligning the heads. So you had to be careful how you adjusted the heads, where you pushed them as you tightened the set screw.
Love the old 9-track tape drives too. Especially the Data General 6026, which used vacuum columns as tape tensioners. It was a beautiful drive. Loved to watch 'em jerk into motion, to seek, retrieve data and return back to BOT.
Quick update - I have created pages on the following computers:
Just finished the Altair page so that reminded me to come back here and mention it. The Altair page talks about "the old days" and it also has a "build" section with links to places to buy parts. It even has a link to a page that documents the entire build process.
]]>Wayne Parham2022-09-22T18:59:13-00:00Re: Microcomputer History
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=96017&th=23133#msg_96017
gofar992022-09-23T01:44:53-00:00Re: Microcomputer History
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=96020&th=23133#msg_96020
You're right that the disk drive cabinet would have been at least 250 pounds. Those multi-platter pack drives had huge transformers for the power supply and a linear motor that was 100 pounds, all by itself. And a fairly large support structure in the cabinet to support all that. So they were pretty meaty boxes.
Back in the day, I considered experimenting with using one of the linear motors from a Data General Zebra disk drive as a big subwoofer. But at 100 pounds, I just never "got around to it."
Linear motor that positions the heads (with shipping head lock in place)
Data General 6061 Zebra Disk Drive
]]>Wayne Parham2022-09-23T19:06:38-00:00Re: Microcomputer History
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=96024&th=23133#msg_96024
gofar992022-09-25T01:40:06-00:00