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Building A Computer From Scratch? 68

Posted by Cliff from the doing-it-yourself dept.
wackybrit asks: "The economy has given many of us the chance to go and work on some side projects. I was reading "Interview With Bill Gates" and have been inspired to create my own computer from parts, to write my own interpreter, and to really see if I could do what Gates and Allen did back then. With the Internet as a reference guide, it should be easy. However, things are not always so easy. I might be a techie, but I have no idea how memory chips hook up, how a data bus really works, and how to tie everything up. Do you Slashdot folk have any handy tips or resources I can refer to for building my own machine from scratch?" If you had a chance to build your own computer, would you make yours similar to existing designs (ala the PC, or the Mac), or would you do it differently?
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Building A Computer From Scratch? More

Building A Computer From Scratch?

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  • Personally (Score:2, Insightful)

    by redcliffe ( 466773 )
    I'd build a mini computer with the functionallity of an 8080, but also some features to make certain functions use less cycles than a normal microprocessor. FPGA's are cool for this.
  • Are you doing this for self-edification(or flagellation might be a better description)?

    Why not try going down a less travelled road. To make a computer from scratch is sort of like building a car from scratch.

    Why not try to find something relatively new? Maybe a PVR. There are plenty of sites that have instructions but it's still a relatively new tech unlike PC's.

    Then again, why should I cast stones/doubt? I'm not coming up with many alternatives.
  • The whole idea of building your own computer is one of those things that people talk about but never end up doing.

    A basic handbook of computer architecture is probably very necessary, so let me suggest the one that everyone's probably read: Hennessy & Patterson. [amazon.com]

    Good luck!
    • Am I the only one that found this book next to impossible to read? Everyone seems to use this book, but I have yet to find a student who thinks it is a clear and consise presentation of the material. Perhaps for a Senior/Graduate course for computer engineers, but when I had to use it for a (poorly taught) mid-level computer science course on architecture, I found it more infuriating than anything else.

      I've found (and understood) good books on Computational Theory, so I figure I am capable of understanding Computer Architecture from a book as well, if it was presented well.
      • This book is quite thick, but with a halfway decent instructor and 3 years of undergrad CS behind me, I found this book very manageable. We used it in our senior CS/CPE architecture course, after each of us had already been through a microprocessors course, a compilers course, a computer organisation course, and a programming lang. theory course. Having those specific courses under our belts made the book digestable.
      • We used the software version in a graduate Computer Architecture class for software engineers. My background is EE,and I found it pretty easy going. Most of the class had CS background and they didn't have any trouble.
      • I agree, I took a computer architecture course using the book last semester and found it verbose (in a bad way) and vague. I don't think graduate students would like it either; the book is simply poor. Fortunately I managed to get by without buying it, so it's not wasting any space on my shelf.
  • i'd grab my handy-dandy C-64 programmer's manual and study the schematic diagram (big thing it is).

    now where did i put that damn thing?

  • Good book (Score:3, Informative)

    by .@. ( 21735 ) on Monday May 20, 2002 @12:02AM (#3548186) Homepage
    If you can find a copy, "Bebop Bytes Back" (found here [doone.com]) is a wonderful book. Despite the childish title, the book will walk you through designing a computer, from scratch. An included CD-ROM provides you with all sorts of routers, simulators, and so forth, including a few IMSAI simulators.

    Even if you don't actually build a computer, you'll feel like you've done when you make it through this book. Bebop To The Boolean Boogie and Designus Maximus Unleashed are also very good tutorials.

    These books aren't going to teach you how to build with off-the-shelf components. They're going to help you understand bus-level logic and so forth.

    From there, you may want to look into the How to Write Your Own Operating System [mega-tokyo.com] page, which will help you get something running on the ahrdware you put together.

  • Go simple (Score:4, Informative)

    by Snowfox ( 34467 ) <snowfox@[ ]wfox.net ['sno' in gap]> on Monday May 20, 2002 @12:18AM (#3548228) Homepage
    Go simple if you're building your first one.

    Use a 65816 or even a 6502. Don't plan on making this your main machine. Just go with what's easy to build, because you're going to make a hell of a lot of mistakes.

    The advantage of a simple processor with a narrow bus and address space and with well-defined behaviors is that you're going to spend a whole lot less time debugging bad traces and similar basic mistakes, and more time getting at the real meat of the system.

    You might also grab a copy of Embedded Systems or similar and grab one of the many microcontrollers advertised therein, with a decent amount of RAM and basic I/O controllers on the chip. Getting memory working involves a lot of busywork, connecting pins over and over and over and over and over.

    Another user suggested getting the C64 programmer's reference manual and looking at the schematic in the back. This would be a good start. Look at at least a few reference designs before anything else. Most of the really old systems had complete schematics available so your average electronics repair shop could troubleshoot them.

    • Re:Go simple - processor (Score:1, Informative)

      by morbid ( 4258 )
      The poster recommends using a 6502. Consider using a Z80 as well. They have their own RAM refresh generator and some internal 16-bit features (e.g. registers pair to become 16-bit BC, DE, HL (16-bit accumulator)) and have a nice instruction set with loops, block moves, block compares, a separate I/O bus and an alternate register set (useful for holding system context), and two 16-bit index registers. The interrupt modes are pretty good too. There are plenty software emulators about that you try out your code on.
    • Bleh. Cheapest I've seen a 6502 is $7, and he'd need logic to do dram refresh. The z80 is $2 at jameco.com, and can do its own refresh.

      Then again, I guess that's moot nowdays... he almost certainly can find a few static 32k's for less than a buck (the cache ram off a 486 works nicely). In that case, 6502 asm is nicer than z80, I never did like the idea of io ports.

      Most modern IDE hard drives aren't easy to interface to an 8bit data bus. Go with a cheap Compact flash chip, which is ide-like and 8 bits wide. Cheap, can get them at walmart, and they have a crapload of storage for a 8bitter.

      Keyboard is tough, I wouldn't want to interface a ps2 to the thing, and yet it's a pain to build your own matrix keyboard (though the concept is simple enough). Maybe a serial port for this?

      Monitor is another problem, but probably a cheap serial lcd would work nicely. Heck, earthlcd.com has some kickass pixel lcd's, in the sub $50 range. Could actually have it do pacman like games and whatnot, if he cared to. Though serial would be simpler.

      Note: Don't listen to the morons that will try to push a Strongarm or something on you... that's an intermediate (or higher) level project.
      • In that case, 6502 asm is nicer than z80, I never did like the idea of io ports.

        If you don't like using io ports, just memory map all your I/O on your Z-80 design.

        Really, the 6502 is one of the weaker 8 bit architectures, and the Z-80 is one of the stronger.

        People like the 6502, IMHO, mostly out of the historical fact that Apple used it on their 8 bit machines. That's not really enough of a reason anymore.

        Or, of course, you could design your machine using my namesake chip as one of the central chips and go all low level TTL. You'll probably want a 74S182 then, too (look ahead carry generator).

        • Yes, the z80 is technically stronger, even I listed several advantages of it (though by no means, all of them). I don't know why I like the 6502, but it's a nice enough chip. I wouldn't want to call it weak, by any means.

          Again, I think that a cpu built out of 74xx is an intermediate level project. I'm not sure that I'm really up to that myself. Not a project he shouldn't pursue, but would be difficult and dissappointing this far along. Definitely something you'd do before trying to implement acpu on fpga...

  • Starting places (Score:4, Informative)

    by arb ( 452787 ) <amosba AT gmail DOT com> on Monday May 20, 2002 @12:25AM (#3548242) Homepage
    First of all you should decide on exactly what you want to do. Do you want to design and build your own computer, or are you happy to build a computer that other people have already designed? I started building other people's designs (the first computer I built was a Z-80 kit computer) and managed to teach myself enough to tackle designing and building a simple 8-bit computer. 8-bit computers are reasonably simple to design and build and there's quite a lot of resources on the net available.

    I would suggest that you look at sites like 6502.org [6502.org], www.coprolite.com [coprolite.com], Mark-8 [his.com], POD 6502 [hccnet.nl] or Grant Searle's collection of sites build your own UK101 [freeserve.co.uk], build your own ZX-80 [freeserve.co.uk] and build your own Jupiter Ace [freeserve.co.uk]...

    These are all quite good sites, and you can study their designs to learn how they work.

    Hope this helps!

  • Bill and Paul had all the time in the world to perfect their craft. They sponged off of their millionaire parents untill they got it right. Microsoft is a riches to riches story - backed by papa Gates's law firm and Momma Gates's political connections and topped off with the Allan family chest of money.

    So if you fail to get your basic interpreter under 4K don't beat yourself up - you probably have a job to go to.

    • I'm all for Microsoft bashing, but this is assinine.

      BG and PA came from privileged backgrounds, but so have plenty of people who didn't manage to build multibillion empires.

      Sure, their family's wealth may have given them an extra cushion (as well as a chance to play with some swell DEC's in high school), but their achievements were on their own in ways that money didn't buy.

      In business, Bill Gates may be an asshole, but he also has a legitimate claim as a pioneer in personal computing. The Gates and Allen did write the first programming language for the first personal computer.

      And Linux Torvalds wrote linux when he had barely a pot to piss in, while living with his mother and sister.

      Money didn't buy any of these people's success.
  • I think this other interview was more revealing:

    • Fucking Crap.

      Some of you boys have a weird fetish on this Gates guy.

      I read that interview, and he really doesn't say anything too shocking.

      All he basically says is that most users don't complain about real bugs, not in a strict technical sense. He does open the possibility that some people don't know how to use their software. Big Whoop.

      He then goes on to say that MS never markets its new versions on bug fixes, but on new features. Again, big whoop.

      Whoever posted the interview doesn't know the difference between bad design and a technical bug.

      I don't know why I'm even bothering (this is the second Gates basher I've taken on in this topic).
      It's just that the stupid, uninformed, deliberately-misleading MS bashing is starting to get dull.

      There are plenty of legitimate MS bashing arguments. But how about moving on?
  • If it were me, I'd write circuit-simulator software and do it in simulation on the computer. Who wants to deal with burnt-out components and other perils of the real world? Plus, this way allows for lots more interesting experimentation, and you get to code up the ICs rather than using off-the-shelf components.

  • It fun (Score:3, Informative)

    by jackb_guppy ( 204733 ) on Monday May 20, 2002 @01:15AM (#3548358)
    I have two of them. Both still work. Z-80 Wire Wrap Motherboards. The first one took almost 6 months to build. The second only a month.

    IT IS VERY BORING TO DO. The first machine has almost 4,000 wires. I made 6 mistakes.

    I got the plans from Kilobaud Mag. They did a three part artical.

  • Been there, done that. (Score:3, Insightful)

    by Animats ( 122034 ) on Monday May 20, 2002 @01:31AM (#3548415) Homepage
    I built a programmable computer out of several hundred telephone relays in the 1960s. The thing occupied six feet of rack space, homebrew paper tape reader and all. It took me two years of evenings during high school. In retrospect, it wasn't worth it.

    If you want to do this today, you might consider designing your own CPU and implementing it with an FPGA. Look into the Forth processors; they're about the minimum useful machine you can build.

    • I have wondered if people did that, in their spare time - was this something for a class project, or was it a hobby?

      In you opinion, how many people typically did this? Do you know of any references to others?
      • I know at least one person who started building his own microprocessor from logic chips in high school. He got as far as the ALU and part of the instruction decoder before losing interest.
        It's one of those things that seems interesting at first, but then you realize your talents are better spent working at higher levels of abstraction.
        • Doing this today (or even 10-20 years ago, though 20 years ago would still be rather impressive) isn't something that "intrigues" me - I mean, I have books on building robots (and attendant CPUs) from the mid to late 1970's.

          But this guy was describing building a computer from telephone relay equipment, etc in the 60's! More or less on his own time, in high school!

          I just wonder how often this occurred - I have yet to find an old Popular Science or Popular Mechanics article from the period discussing such projects (ie, homebrew computers from the 1960's) - the closest I have found was a telephone dialer system for an alarm (with complete plans for a rotary telephone), and a later book detailing building a simple calculator based on transistor logic (from the very early 1970's). I haven't found anything on people homebrewing machines in the 1960's from scavenged telephone equipment parts.

          It isn't that I don't believe it impossible - I know full well that people could do this, and knew that at least a few people had done it - but how many? Was any of these efforts documented?

          The closest I have come to "early homebrew computer documentation" was an old stapled, photocopied "pamphlet" from 1975 (I think) detailing how to build a computer "from scratch" - even so, it detailed info on logic circuitry, etc (74xx series), and so wasn't in the era of relay logic.

          I tend to think that some of these people who possibly built such machines might have been technicians who worked on "relay ladder logic" for process control, and came home to build similar systems, but with their own curious designs - but this is just a theory, with no proof in any manner...
          • I picked up an Electronics Illustrated magazine from 1959 at a flea market a few weeks ago. The cover story was a 'build your own computer' project. Basically the design is to build a set of cascading flip-flops using discrete transistors (they used big heat sunk TO-3 transistors for some weird reason). The input device was a few toggle switches to select 'operation' and a telephone dial to enter numbers. Basically just a simple flip-flop based binary adder. But I bet it was cool to have back in 1959.
  • The MIT 6.270 project [mit.edu] course has been running for a long time. When I was an undergrad, they has a very cool design for a Motorola 68HC11 based SBC that was perfect for motor interfacing and various small scale projects. These days, the same architect (Fred Martin) has a modernised version of the original 6.270 SBC available at HandyBoard.com [handyboard.com] and there are variants of the original SBC with it's documentation here. [handyboard.com]

    Other posters who suggest that you do some studying are not unwise. Digital logic is straightforward when you have a background in combinatorial logic and a few other concepts up to about 25MHz. Designs with that level of clock speed can easily be wire-wrapped. Beyond that, you are going to have to start considering high-speed design issues when you route your boards.

    One of the most rewarding things that I did as an undergrad was design my own SBC around a Motorola 68HC11 to run the mechanics for a 3-D scanning system that interfaced to an SGI workstation.

    I really think that if this interests you, you should pursue it . The current 'state of the hobby' is now so advanced that it is somewhat mind numbing what can be done with some FPGAs and some software to layout a PCB.

    The Motorola Dragonball family (or it's decendants) are an excellent 68000 core family of chips that are easy to use and you can design a modestly useful machine around them with a classic buss / memory mapped IO architecture without working up too much of a sweat.

    Good Luck!

  • Start small (and simple) (Score:5, Informative)

    by Restil ( 31903 ) on Monday May 20, 2002 @02:19AM (#3548552) Homepage
    Assuming you're doing this for the educational experience and not because you plan to end up with a powerhouse computer when you're done, your best bet will be to build something on the scale of the Apple II. The first bit of good news, the parts necessary to build it are dirt cheap now.

    The first thing you need to do is to understand all the logic gates and how they work, and then work with the various logic gate chips (the 74 series) to get various simple experiments working. This will get you familiar with HOW the circuits are passing information around, as well as give you some experience with wiring the components together in a useful fashion.

    After that, CPU's and memory are just largescale versions of your typical logic chips. Of course, its not as simple as it sounds and you definitely have your work cut out for you if you plan to do it completely from scratch. If you want to follow some old schematics your job will be simpler, but that might defeat some of the purpose.

    As for programming, you'll be starting at the raw assembly level. You'll also need some type of interface to input and view data, as well as storage. In the beginning, you can use programmable rom chips to hold enough operating system information to get you going. Yes, you will have to develop at least a simple operating system.

    Hope I didn't scare you too much. If you manage to get all that working, you'll be in a great position to move onto something more complex. Today's computers won't even seem that complex anymore, it will simply be a matter of scale.

    -Restil
    • re:
      The first thing you need to do is to understand all the logic gates and how they work, and then work with the various logic gate chips (the 74 series) to get various simple experiments working. This will get you familiar with HOW the circuits are passing information around, as well as give you some experience with wiring the components together in a useful fashion.

      Whilst you're reading up on this you'll probably find that most electronics text books include chapters on computers.

      My personal favourite "The Art of Electronics" [artofelectronics.com] by Horowitz and Hill walks you through an example of incorporating a 68008 (I think, I haven't actually got my copy of it available at the moment) into an instrument (ie. specialized rather then general purpose computer) they construct in chapter 11.

      If you want to start off really simple (think more of really simple programable calculator kind of level) then something more along the lines of a PIC 16fxx microcontroller from Microchip [microchip.com] is a good starting point, as you can have something up and running very quickly with just a breadboard, the microcontroller and a handful of discrete components (and maybe some LED's for output) using a PC to program the device, and then slowly add to the base design with some external memory, and LCD display, a numeric keypad for input, and so on ...

  • m68k cpu (Score:3, Insightful)

    by StandardDeviant ( 122674 ) on Monday May 20, 2002 @05:27AM (#3549004) Homepage Journal
    This is also a project I've been idly thinking about for a while, simply for the challenge. :-) (So, you're not alone or crazy, heh.) I've been thinking of using an m68k cpu, for a couple of reasons:
    1. It seems like everybody was using them in the mid 80s to early 90s (sun, amiga, macs, next, just off the top of my head). This means that a) they're probably easy to design around, b) they've probably got LOTS of public-domain documentation, and c) they're cheap ;-)
    2. The initial versions of SunOS as well as all the versions of NeXT ran on m68ks, so I know it's possible to run a Unix-like OS on them.
    3. I've been told that m68k assembly is comparatively easy and straight-forward to learn, and I'm going to have to hack at least SOME asm to get an OS going on my theoretical creation.
    4. Did I mention they're cheap? ;-) At maybe five bucks per good chip on ebay, I can afford to fry quite a few of them
    Of course, I'm just a software dude (actually, my formal training is in chemistry, I just sort of fell into programming), so if any hardware people are in the audience hopefully they'll correct any stupid assumptions I've made.
    • An undergrad course I'm taking right now use 68k8. (A slightly cheaper version of the 68k; it has fewer interrupt levels for instance.) I can certify that it's a really nice CPU to work with. (Not that I've tried all that many others. ;-)

      To get a simple computer board going you only need a 68k8, some ROM and RAM and some programmable logic circuits. (To control the signals to ROM/RAM circuits.) When we started on the project it seemed rather hard, after only a few weeks now I'm confident that we could have done a lot more fun stuff. (Given the time to do so naturally.)

      We're creating a MOD player btw, this involves some slightly more hardcore circuits, mainly a medium sized Lattice (FPGA).
    • Unix for 68k? NetBSD ;) Just some porting needs to be done for your own firmware... And offcourse, as you probably will use only serial terminal as input/output... Well on another thought you will need some ROM to store NetBSD on... and... you know... hobby machines have never been and never will be heavy-artillery in desktop market... or smth..
      • Yeah, that's another implicit reason. If I get lazy about writing my own OS to run on the hardware, I'd have something to fall back on... ;-) Come to think of it, it probably would add some jazz to the NetBSD team to be able to say "we run on XX arches, even a custom built one, just for us" heh. not that anyone would ever use the theoretical machine as more than (at most) an X term, but distributing all the plans and parts lists and whatnot along with the distribution would be a pretty cool thing for hobbyists and students to fool around with...

  • Gates may be good at taking credit for others... (Score:5, Informative)

    by Alex Belits ( 437 ) on Monday May 20, 2002 @07:36AM (#3549257) Homepage
    ...but it's worth to remember that "standing on the shoulders of giants" applies to anything related to the computing that actually works. One man making a big show out of making, of all things, BASIC interpreter for hardware made by others, doesn't mean that something decent can be built from scratch without serious learning and existing components.

    I have seen second or third-year MIPT (Moscow Institute of Physics and Technology, in Russia) students building 8080 or Z80-based computers in 1987-89, and tweaking a lot of hardware and software in them, but I don't know if that can be really described as "from scratch" -- at that particular place there were two or three dominant base designs, with some simple "OS" written by different people, including a bunch of BASIC interpreters, editors, assembler, etc. (those things were too small to run CP/M). Making those things required mostly knowledge of electronics plus understanding of microprocessors, knowledge of 8080 instruction set, and some programming skills, not necessarily all in one person, and when I studied there I have seen, I think, about one of those things per four-people dorm room. Of course, that was in the FRTK (mostly EE) students' dorm, and at the time the most common computer that we used at the school was a russian clone of PDP-11.
    • I built an 8088 based SBC by hand as my senior design project in high school. It had bugs, but I was able to latch the data bus to a few leds, and make them count up from zero.I could have made something useful, if I'd had more time to spend with it.

      All you need is the intel docs, really. There are oodles of schematics on line, as well as a number of books on it.
  • Well, its interesting that you bring this up since this was the final project I had in college Electronics. Its actually a pretty long project, but very fun and educational. First thing is to decide on an achitecture in which to build your system on, then find as much technical information on the device as possible. I went off an 8086, and finding Intels technical documentation for this isnt very hard. From the pin outs, you can kind of start to figure out what you want your device to do. Mine didnt use any disk I/O, it used serial based communication, so in addition to memory, DMA, ect ect, I had to find the correct UART for the serial device. Its been some time since Ive actually done this though. But finding the documentation isnt very difficult, and when I did this I already had 4+ years experience in computer/electronics, and the 2 years of college to add to it. If you get a basic understanding of digital logic circuits, the rest kind of falls in to place if your willing to do lots of reading and persist in your efforts. Best of luck....

  • A different starting point - divide and conquer (Score:3, Insightful)

    by dpilot ( 134227 ) on Monday May 20, 2002 @08:06AM (#3549364) Homepage Journal
    There are really two issues with what you want to do. First is digital logic and computer design, the second is hardware design and practice. The last word, "practice", is an especially tough nut. One other poster talked of wire-wrapping and messing up 6 connections out of 4000. I would suggest splitting this project into two phases, to be tackled in no particular order.

    One Task: Learn about hardware construction on some simpler projects. Learn by building from working schematics.

    The Other Task: Learn about computer design with simulation. Go get Icarus Verilog. (http://www.icarus.com/eda/verilog/index.html) There are microprocessor netlists available, get one. (Don't have a URL handy.) Learn to simulate it, learn Verilog, (or VHDL) then start designing your own.

    Put the Two Together: Once you know how to work with hardware, and once you have a design that will simulate correctly, start thinking about building it. Besides, this is the way it's done in the Real World. Nobody comes up with a schematic, implement it in hardware, then begin debugging, any more. You don't start to touch hardware until you have a reasonable belief that your design will work, from simulation. Even then, there will still be plenty of room for debug on hardware.

  • One book to buy.... (Score:3, Informative)

    by erf ( 101305 ) on Monday May 20, 2002 @09:50AM (#3550065)
    "The Art of Electronics" by Horowitz and Hill and its companion book "Student Manual for the Art of Electronics" by Hayes and Horowitz.

    This will walk you through analog and digital circuit design and construction, and culminates with the building of a 68000 based fully functioning computer with I/O, buses, the works.

    I had the pleasure of taking an electronics course taught by Mr. Hayes, and building your very own computer is fun. It is also time consuming, complicated, and frustrating. You'll also need a moderate amount of equipment such as an oscilloscope, power supply, function generator, DVM, and the like.

  • Gates and Allen (Score:2, Informative)

    by qurob ( 543434 )
    Although they DID write BASIC and other language for a ton of machine, they didn't 'build their own computers'.

    You're thinking of Jobs and Woz
  • I can't believe nobody's mentioned Doug Jones' Ultimate RISC yet. a 16-bit version can be built with about 50 chips or so (I'm working on one now), and they don't get any simpler than this one-instruction machine!

    Jeff
  • Build your PeeCee exclusively out of DSP cores (and any necessary passives for the interfaces)...

    That'll keep you busy for awhile.
  • You will need that, and more (lots and lots of patience, primarily) to pull it off. I am not saying it is impossible, but it will be frustrating.

    First off, read all of the comments here, they contain good advice.

    Second, realise this, which I have rarely seen talked about:

    Computers are nothing more than extremely complex player pianos.

    Honestly. Think of memory as a very long (but non infinite, though it can be considered an endless loop, because when the address register of the machine "rolls over", you start at address zero again) roll of player piano music, the holes representing instructions and data, and the rate at which the computer runs (the clock) the speed at which the roll is moving (tempo?).

    Anyhow, that is all a computer really is - sure, some instructions may say "move to this point on the roll (address)" or "play this note (add this number to this register)" - but all in all, it is the same.

    Most of what computing is today was thought out in mechanical arrangements by Charles Babbage in the 1800's - because computer ARE inherently mechanical (read the book "The Difference Engine" for more).

    Now, this doesn't explain how modern processors work. Modern processors perform some extreme "magic" - but most of what they do isn't that arcane, and you certainly aren't suggesting that you want to build an 1.5 GHz Athlon or something (and you would be insane to try to do that at home).

    One thing to keep in mind is that if you are doing this at home, don't try to go much beyond 2 MHz - otherwise you will drive yourself batty trying to figure out certain problems that only appear when you run at full speed vs single stepping the clock, etc (ie, speeds of signals in the bus not arriving at proper times, etc) - if you are thinking about building such a faster machine without a logic analyzer (I think that is right - kinda like a combo logic probe with multiple inputs and an oscope like trace screen), you will be in for some surprises (read "Soul of a New Machine" for fun in this regard).

    Good luck - and remember to document your progress, and let us know about it!
  • FPGAs? or ENIAC/EDSAC/an early UNIVAC/Burroughs/CDC/PDP/DEC or Knuth's MIX machine emulated in FPGA? That way you learn all the Good Stuff (Instruction set implementation, architecture, microprogramming, embedded software - and some history too!) without the enormous pain of dealing with soldering, Electro-magnetic compatibility, signal integrity, physical clocking, board layout. Working with modern day small chips,. Ball Grid Array and Surface Mount chip packages are not for do-it-yourselfers! Save yourself a lot of needless pain (& waste of money) with no corresponding learning (unless you want to become a board design expert) and go FPGA emulation route.
  • ( designed ) - just never built them.

    The first was a group of 7400 logic chips wired together to form a 6-bit computer with a real simple instruction set. I'm pretyt sure it would have worked properly - had access to memory etc.

    The second was really a C64 and all of it's components re-designed / simplified. I added banked memory / a lcd controller driver etc.

    I was always too lazy with these guys to actually build the stupid thing. I now look back and wish I had built the 6-bit 7400 one...

    *sigh*

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