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Simple CPU

simplecpu.com

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Re: Simple CPU

#41

Post by dagw »

ajkjk wrote: post #36
noonespecial wrote: post #26

Earlier quoted context omitted.

I don't know. I heard about nibbles right at the beginning and then promptly forgot them. I even remember thinking that the word was silly. But it set me up for a very nice epiphany the first time I saw bytes written as hex and played a part in my instantly grasping that.

I'd be curious to poll people's experiences, but, I can say that I had never heard the term until today and I've known this stuff for a number of years. And it sounds silly and adds nothing. That too. (edit: my education on this stuff was in the 00's. Sounds like it was more common in the 80s. I'd definitely support obsoleting the term entirely now, though! It adds unnecessary complexity.)

While I haven't heard or thought about the term in years, I do remember it from learning about computers in the 80's. I guess it made more sense back in the days when binary math and bit twiddling where a more common technique and keeping close track of the number of bits you where using was important.

Re: Simple CPU

#42

Post by muyuu »

HanyouHottie wrote: post #22

I thought this was pretty clever: 00000001 A program that doesn't work if you move its location in memory is pretty hilarious.

That was extremely common in 8-bit days. But then again it was commonplace to destroy userspace upon loading of programs and you finished your session by either resetting the computer or turning it off (1~2s boot times helped though).

Re: Simple CPU

#43

Post by rdc12 »

wazoox wrote: post #15

It's very similar to Charles Petzold's "CODE" book. An excellent read. http://www.charlespetzold.com/code/

I found it easier to understand how the d-latch worked from this they Petzold's book, probably because I could see the changes vs working it out and having to convince myself I was reading it all right.

Re: Simple CPU

#44

Post by rdc12 »

ajkjk wrote: post #36
noonespecial wrote: post #26

Earlier quoted context omitted.

I don't know. I heard about nibbles right at the beginning and then promptly forgot them. I even remember thinking that the word was silly. But it set me up for a very nice epiphany the first time I saw bytes written as hex and played a part in my instantly grasping that.

I'd be curious to poll people's experiences, but, I can say that I had never heard the term until today and I've known this stuff for a number of years. And it sounds silly and adds nothing. That too. (edit: my education on this stuff was in the 00's. Sounds like it was more common in the 80s. I'd definitely support obsoleting the term entirely now, though! It adds unnecessary complexity.)

My algorithms teacher (3rd year paper) mentioned them when doing a few lectures on information theory, data compression and encoding, then set an assignment on implementing LZW or LZ78 with a bit-packer (and the inverse). The spec allowed you to either compress via bytes or nibbles.

That was last year, I also got the impression that he liked to fill likely gaps that he could do with small detours.

Re: Simple CPU

#45

Post by jhdevos »

mockery wrote: post #10

This is awesome. "You can scroll through memory as well" --> Would be nice to have a scroll-bar because I missed this at first and wondered why there were only 6 bytes of memory. (Would also be nice to see a bit more of the memory at once, although then the instructions might be easy to miss. Maybe a "show more memory" check-box?) Would also definitely be nice to reset / modify the instruction pointer. And of course…

A button to execute a single instruction would also be nice.

Re: Simple CPU

#46

Post by couchand »

ajkjk wrote: post #36
noonespecial wrote: post #26

Earlier quoted context omitted.

I don't know. I heard about nibbles right at the beginning and then promptly forgot them. I even remember thinking that the word was silly. But it set me up for a very nice epiphany the first time I saw bytes written as hex and played a part in my instantly grasping that.

I'd be curious to poll people's experiences, but, I can say that I had never heard the term until today and I've known this stuff for a number of years. And it sounds silly and adds nothing. That too. (edit: my education on this stuff was in the 00's. Sounds like it was more common in the 80s. I'd definitely support obsoleting the term entirely now, though! It adds unnecessary complexity.)

It's yet another term that you can get by without knowing, and you'll probably be fine. But understanding why it's relevant to even have a word for it is the important insight. We should just as soon obsolete the term flip-flop.

Re: Simple CPU

#47

Post by michaelmior »

AndrewDucker wrote: post #6

The memory scrolling doesn't work in FF - you can only see the initial 6 locations... And he's fixed that. Awesome! Also - it would be very neat to have a "reset" on the Instruction Pointer, so that you don't have to refresh the current page if you want to start your program over...

This is fixed in the sense that I can now scroll through the memory, but the page scrolls at the same time, which makes it a little awkward.

Re: Simple CPU

#48

Post by KeriWarr »

I was attempting to create the most simple infinite loop that I could, and found that the instructions do not work in the way that I thought they would. Here are a couple programs I wrote. If someone could explain why they work the way they do..?

00000011

00000100

00000000

00000001

Looking at this, I expected that it would read line one, then move the value addressed by line two to the value addressed by line three. i.e. set the instruction pointer to 00000001. This didn't work. What did was:

00000000

00000000

00000000

00000011

00000111

00000000

00000001

This program advances to line 4 then remains there. Could someone explain why program two is an infinite loop, but program one isn't? Thanks!

Re: Simple CPU

#50

Post by r00nk »

KeriWarr wrote: post #48

I was attempting to create the most simple infinite loop that I could, and found that the instructions do not work in the way that I thought they would. Here are a couple programs I wrote. If someone could explain why they work the way they do..? 00000011 00000100 00000000 00000001 Looking at this, I expected that it would read line one, then move the value addressed by line two to the value addressed by line three.…

Hi, I made this site.

The problem is that it moves that value into the instruction pointer, then the instruction pointer increments itself by 3.

the instruction pointer always increments itself by 3 after every instruction.

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