Magic 1 was what inspired me to start the project, I continue to be in awe at the ambition of Bill's project. Watch this space for a more technically focused post.
It awed me as well. Plus, the performance and such gave me inspiration that homebrew might be an answer to non-subverted computers post-Snowden. At least, for the bootstrapping phase of other computers, SCM/builds, or key storage.
Only thing was that a HW guy told me the TTL chips he used might be hard to come by. I looked them up and had trouble finding them. So, rather than cloned, the next Magic 1 should be ported use components currently available... preferably 10 year horizon. Also, ideally something fabbed at 0.35 microns or above for visual inspection. Plus realism, as we're practically cheating if you're using deep submicron for "hand-built, old-school" systems.
What kind of primitive components are you using or found consistently available?
I really wish he'd document even the barest scraps of the CPU architecture. Is it microcoded? There's 7400 series like 7402 or 7473, and there's 7400 series like 74154, 74181, etc.
"hey kid, I built one of these too, back in the day, and it was damn hard and time consuming, but oh a labor of love. I had no internet, nor any schooling. I read articles in Popular Electronics and I read the TI 7400 series databook. Then I reread them. Then I reread them." Yes, in fact it was snowing, uphill, and I in fact had no shoes!
Completely agree, this was just the first foray into documenting this project and I wanted to make it less heavy on the details of the hardware to reach a wider audience. I'm definitely going to put up a more technical post and the sources/schematics as soon as I can.
To answer your questions, it's hard wired with the control logic made out of the simpler chips (7400, 7408, 7432 etc) but the rest of the system does contain more complex chips, the 74181 ALUs being the largest.
Judging from the small number of chips in the photograph, they used the higher integration 74 series logic rather than the lower level flip-flop/NAND type.
> Built from simple logic chips, it runs at a blistering 4MHz, has 32kb of RAM
I know that the author was being sarcastic, but really, 4MHz with 32kb of RAM is like state of the art 80's technology. The fact that we are even able to get to this point with protoboards and discrete off-the-shelf logic chips is impressive.
I mean, I learned how to program back in 1988 in a computer not much more powerful than that.
It's a wonderful, in fact an astonishing course. I hope that when they come out with part 2, it really does go all the way to Tetris. The "nand" bit is a slight fudge (they actually start you off with both nand and a flip-flop, which is still amazing), but we can grant them a bit of poetic license on that. But not on the Tetris!
I wonder if this had something to do with someone I countered a day or two ago thinking all you needed was a NAND gate to do anything. I said you need memory and some other things for most hardware. Maybe that commenter got the idea from this project's name...
Yes, and in one of their Coursera videos the nand2tetris guys sketch out how this works. But I wish they'd have included it in the course itself. Maybe it would have needed an extra chapter, but for those of us who never studied it before it's really cool stuff.
That's neat. Lets test the rest then. Full claim was a computer needed logic cells, RAM, ROM/flash, and analog components (eg I/O & power-related). Still only need a NAND gate? ;)
Agreed, this is super cool. I've read the book "Code" a few times, so I understand a lot of this stuff in theory, but I sure don't understand the practice. Awesome work.
I read code a couple of times and did Nand2Tetris. I also found the edX 6.004 mit course[1] to be extremely useful to fill in some of the gaps. I'm waiting for part three to start in a couple of weeks.
Does it do pipelining, branch prediction and (hyper)threading? How is its memory hierarchy (cache levels) organized? Does it support a privileged mode? Does it support hardware page faults? Did you implement floating-point operations?
> In order to be able to program it at all, I wrote a very simple compiler (strictly speaking it’s actually an assembler)
Does that compiler/assembler run on your hardware?
In a word: no. Processors this simple don't implement any of the features you mention, including multi-level memory hierarchies, and I doubt the author had any inclination to make the assembler self-hosting.
I'm not saying one should expect or demand it in a project like this, but minimalistic pipelining should be doable; both the 6502 (http://www.6502.org/users/andre/65k/arch.html#pipelining) and (IIRC) the 8080 started fetching the next instruction before finishing execution of the current one, where possible.
@ All
This is how you do homebrew CPU's and presentation best:
http://www.homebrewcpu.com/
Links to others for anyone wanting to learn about this stuff:
http://www.homebrewcpu.com/links.htm