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In my student days - this was in 1979 - one of the lab exercises were with an AMD 2901 Evaluation Kit. The 2901 was a 4-bit "bit slice" ALU, with carry in and out, so you could hook two of them together for an 8-bit machine, four for a 16-bit or 8 for a 32-bit. We had only a single one.
With the ALU came a memory for 64 words of 16 bit microcode: Flip 16 switches, press Deposit, flip again, press Deposit ... 64 times to fill the entire microcode memory. We hooked up each of the 16 bits to the control lines for the ALU: Load accumulator from bus, dump accumulator to bus ... actually, today I have only a vague memory of what the control signals were. The 'sequencer' was a separate chip that selected one word from microcode RAM, transferring it to the ALU control inputs. It had a microcode address counter; one of the control signals incremented this counter.
We did succeed in microcoding an instruction for reading four switches (the "bus") as data, adding another 4 bit value, and display the result on 4 LEDs (plus one for the carry line).
This was an exceptionally valuable lab exercize to learn what (an extremely simpified) CPU is like in its very basic mechanisms. If 2901 Evaluation Kits were still on the market, I would recommend it to anyone who wants a true hands on experience with a CPU. (If you happen to find one on eBay: Be prepared to do some thorough studying of the ALU before trying to microcode it; microcoding is not to be don on intuition!)
Of course: Anything like the 2901 kit can teach you only the basic techniques of simple, unsophisticated computers, the way they were built in the old days. I see other people refer to 'modern' CPUs as if they have little to do with what an evaluation kit can teach you - but you can immediately forget jumping directly onto a 'modern' CPU. It is so complex, contains so many fancy tricks for speeding it up, that you will be be completely blown down. Better start with something that you have a chance to really understand, and then add the fancy techniques one by one. If you get as far as to thoroughly understand even a third of them, you will be qualified as Chief Engineer at AMD or Intel Or, to phrase it differently: Don't expect to understand the fancy techniques. You may get as far as to understand what they want to achieve, but don't expect to understand how.
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I remember bit slicing processing and the 2901 set. We also do some similar exercises. I agree, modern CPU's are much more complex, but the AMD 2901 exercises really help one to understand the basics that almost all CPU's have in common. I also agree, micro-coding is not intuitive and that was why we were getting a lesson in it.
WOW blast from past. Thanx for sharing that.
"A little time, a little trouble, your better day"
Badfinger
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all your assumptions are both correct, and are over-simplifications of what modern CPU's are, and do.
maybe do some reading on Von Neuman architecture [^], and what a Turing Machine is [^].
«The mind is not a vessel to be filled but a fire to be kindled» Plutarch
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Doesn't exactly anwser your question, but Ben Eater has a series of videos where he builds an 8-bit computer on breaboard starting with a chip
Ben Eater Build an 8-bit computer from scratch
Gives a lot of insight into the workings, there are a couple of specific videos below, but the whole thing is fascinating.
The first thing is the CPU is powered - the microchip has a ground and dc positive pin. If you think about it interms of electronics, what is a "0" or "1": 0 is easy, it's ground voltage, but 1 needs to be voltage close to a reference - which the +ve provides. This dc reference voltage also provides the power to keep the values in the register. There isn't any flushing - the Clock (which is just a square wave) just gets the CPU to cycle.
“Hello, world” from scratch on a 6502 — Part 1 - YouTube
This video tells you how CPUs actually execute machine code
How do CPUs read machine code? — 6502 part 2 - YouTube
Hope this helps - the videos are right on the edge of electronics / programming. Bill Woodruff's suggestion about the von Neumann architecture and Turing machines is excellent, it explains how we got to 8 bit chips
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Dolly Parton is 77 today.
I'm not really a fan of her music, but I adore her just the same.
Edit: I just found out:
She's getting into the Rock & Roll Hall of Fame.
Her reaction was "I guess I better actually make a Rock & Roll album". And she is.
Ha!
To err is human. Fortune favors the monsters.
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She is a legend for sure. Love the music she made with Linda Ronstadt and Emmylou Harris.
"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
"I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle
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She's an example of how celebrities should be.
Jeremy Falcon
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Jeremy Falcon wrote: She's an example of how celebrities should be.
This.
I don't mind some country music, but TBH there's only so much of her albums I can take.
That being said, I would NOT let anyone say a single bad word about her. As a human being, she's what a lot of people should aspire to be.
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My kids have all benefitted from her Imagination Library, so I certainly have some admiration for her.
A friend of mine works at her theme park, Dollywood. He's mentioned that she's quite a lovely and respectful person.
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If I remember correctly she's turned down a nomination to the Hall of Fame several times.
Zach
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It really made Joe lean, Joe lean, Joe lean, Joe leannnnnnn....
(Joke aside, this is one of my favorite songs. Especially the Miley's cover).
Advertise here – minimum three posts per day are guaranteed.
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Ouch.
Just the joke… I also like that tune.
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englebart wrote: I also like that tune.
And the story behind it[^] is so much Dolly Parton... truly an icon.
Mircea
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It took me a couple of seconds.
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She was officially inducted on November 5 last year.
Kelly Herald
Software Developer
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Oh, well I'm just repeating what I heard from a friend. *shrug* Guess I was wrong.
To err is human. Fortune favors the monsters.
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Nice lady and singer, and does a lot for the world through her charities. I was surprised to hear about her Confederate-themed diner. It has changed formats, and is not (as?) offensive from other articles I've read, so she listened to criticism and is growing. Gotta respect that, too. I wish her well.
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That's totally on brand. She's a class act. I don't expect her to be perfect, but she always seems to want to do right by the world - going out of her way to. I admire that about her immensely.
To err is human. Fortune favors the monsters.
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If you know her life history, especially early on, she was made of very tough stuff. Class act indeed.
"A little time, a little trouble, your better day"
Badfinger
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When I visited Gatlinburg on the way to the Smoky Mountains I was told that no matter what political affiliation you have in Tennessee. "No one speaks bad about Dolly".
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So you have some freedom of speech, but it doesn't go that far ...
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Wait - you mean the actress from that one episode of "The Orville"[^] is going to start a music career?
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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If you were on the side of the road, Dolly Parton would stop and help change your tire.
Same for Keneau Reeves. They are both legendary, and they are humble.
There is your nugget - be humble.
Charlie Gilley
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759
Has never been more appropriate.
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Are you kidding? I'm the most humble person I know!
To err is human. Fortune favors the monsters.
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