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I would like to build a computer. It is a child's dream that I had and now that I am at college, I finally gain the knowledge I need.

I want it to be simple. I admire the early designs of 1990's notebooks and I imagine building something like that myself. I think it could be interesting to build a device with limited computational power, yet gain the advantage of using highly-integrated components available today (instead of hundreds of single purpose ICs).

I would write a very simple operating system myself, firmly tied to the actual design to run efficiently, as well as few other programs I cannot live without (vi clone for start).

When I wanted to buy a new notebook eight months ago, I did not find anything that would make me happy. Here's what I want from a notebook to have fun:

  • 60 MHz CPU
  • 8 MB RAM
  • 256 MB non-volatile storage space
  • monochrome VGA resolution display
  • 10 hr battery life

Only high-end notebooks or simple netbooks have the required battery life. Small netbooks kill ergonomy (I really love large keyboard), high-end models are expensive (Lenovo is close to what I need). I decided to keep my old SONY VAIO VGN-FW21Z and gave up on buying a new notebook.

(Note: The moment I start xorg, the fan gets a little loud. I always think: why do I feed the CPU with so much energy and keep it cool all the time, if I only need a fraction of its actual power? It is my strong belief that a vast amount of the power of today's PCs is totally wasted for nothing while having super-fancy logos and trademarks all over the damn shiny chassis.)

Designing my own computer from beginning to end would be partially a great exercise, partially I would like to build something that fits my precise needs. It would be great fun of course.

Recently, I have been through discussions on the topic of CPU selection.

  • ARM processors seem to be way more powerful than I need
  • Texas Instruments offer MCUs that seem to be designated for real-time control and floating-point performance
  • Atmel MCUs (AT32UC3C0512C in particular) seem to be the best fit

What confuses me is this. The AT32UC3C0512C is SoC device that itself incorporates main memory (68 KB SRAM), A/D converters etc. I would really like to wire my own RAM modules and drive them myself rather than having them on the chip already. The same applies to most of the other peripherals already contained in the package.

It seems I would need the sole UC32 CPU. My question is - is there a simple CPU operating around 60 MHz with solid architecture that I would use in this project? I am not looking for legacy components.

By the way, if you have any experience you can share, I kindly ask you to post a link to it.

Nice hacking!

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closed as too broad by Matt Young, Dave Tweed, Anindo Ghosh, Leon Heller, Daniel Grillo Nov 22 '13 at 11:05

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ "Designing my own computer from beginning to end would be partially a great exercise..." Don't take this the wrong way because I do think it is a great exercise but what you describe isn't designing your own computer from beginning to end. Here's what that actually entails: homebrewcpu.com Still, I think your project is interesting. \$\endgroup\$ – Alfred Centauri Nov 22 '13 at 0:12
  • \$\begingroup\$ This is absolutely astonishing. Maybe building a simple portable computer the way I proposed above will one day result in such a beautiful project. Right now, I know I would not be able to make it. Thank you for the link! \$\endgroup\$ – David Nov 22 '13 at 0:20
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    \$\begingroup\$ I find it astonishing too as I felt sure you would. By the way, you can telnet in to his homebrew minicomputer and, among other things, play "Adventure". I must confess I do this from time to time. \$\endgroup\$ – Alfred Centauri Nov 22 '13 at 0:38
  • \$\begingroup\$ I'll second your choice of AVR32 as a base architecture. \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 22 '13 at 1:39
  • \$\begingroup\$ CPU design and computer designed diverged a generation ago; it's not real likely the same engineers would be trying to do both today, as even an eval board for a modern CPU is going to need a substantial experience-skill set in board design wholly distinct from that of ALU, etc design. \$\endgroup\$ – Chris Stratton Nov 22 '13 at 18:12
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If you want to find a device with a minimal amount of on-board peripherals and an external memory / data bus then "MPU" or "Microprocessor" is a good term to search for on supplier websites. For example the following is the embedded microprocessor page at Digikey:

http://www.digikey.com/product-search/en/integrated-circuits-ics/embedded-microprocessors/

If you use the parametric search on that page the problem you'll find is that a lot of simpler ones that fall roughly inside those specs are obsolete. Most of the current more capable ones run at a higher clock rate and come in BGA packages that would be harder to work with and are generally more complex. That's not suprising because most modern commercial designs would either benefit from the integration of a microcontroller or require something at the higher-end where design and manufacturing complexity is less of an issue.

I'd probably stick with a microcontroller similar to the one you've already found with an external data bus / SDRAM controller to attach external RAM. You could also do the memory interfacing directly using I/O pins. For the peripherals you can always choose what on-chip peripherals you use versus what you add externally. You'll probably find plenty of challenges such as attaching the VGA LCD to keep it interesting.

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  • \$\begingroup\$ Thank you for your response. I will look at Digikey first and if I found nothing, I will stick to the MPU I proposed. \$\endgroup\$ – David Nov 23 '13 at 20:09

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