What all is needed (in knowledge and software) to make a small pcb design interfacing processor and external memory and other ICs? Is it possible to make such a thing virtually and give it to a manufacturing company for making it? Are there any open source customizable hardware models which can help?
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1\$\begingroup\$ Depends: Are you talking about an ATTiny running at 2 MHz interfaced to 4KiB of external SRAM, or are you talking about a 3 GHz Intel interfaced to 16 GiB of external DRAM? \$\endgroup\$– us2012Jul 20, 2013 at 13:01
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\$\begingroup\$ something like 1GHz ARM or Cortex processor with 512MB RAM \$\endgroup\$– Abhinav MukherjeeJul 20, 2013 at 13:09
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1\$\begingroup\$ I don't think that's a realistic goal if you don't have vast prior experience. Creating a PCB design and having it manufactured is not a problem (the manufacturer will happily produce anything you pay for), but getting the design right so it will actually work is a big problem. If I were you, I would look around for evaluation boards or minicomputers with your desired specs. (Maybe some Cortex vendors even provide reference designs?) \$\endgroup\$– us2012Jul 20, 2013 at 13:42
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Given your baseline of 1GHz ARM you are looking at a multilayer board (8 layers say) with a high pin count BGA package. An AM3539 is a 324-Pin PBGA package. Assuming you don't go package on package for the memory, you are looking at an awful lot of high speed interconnects, all of which have to be balanced and impedence matched. You'd start with a 5 grand licence for Altium Designer or something similar.
You can have a look at the hardware platforms like the Beaglebone and the Pandaboard which will give you an excellent idea of the scale involved. There are some terrifying videos on YouTube (example) showing you the routing involved with DDR3.
What I'm doing currently is designing a baseboard around a SoM - a system on module (A Gumstix). All the horror is taken care of, yet you have a lot of low level access to pins.
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1\$\begingroup\$ So, if you make an expansion board for a Gumstix COM and make a product out of it, can you commercially sell the product? Or is gumstix coms only for hobby use? \$\endgroup\$ Jul 20, 2013 at 18:21
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\$\begingroup\$ That's a question you should ask Gumstix, they'll happily provide you with an answer. The T&C that I can find on their website look friendly to hobbyists, but difficult to resellers. But there surely are dozens of companies out there that will happily sell you Cortex boards that you can sell on with your extra hardware. \$\endgroup\$– us2012Jul 20, 2013 at 19:24
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1\$\begingroup\$ It can, in principle, be done using free software. The required skill level, though, likely then spikes much higher since things like gEDA doesn't have tools that Altium presumably has to help with routing wide high speed parallel busses and such. \$\endgroup\$ Jul 20, 2013 at 22:03
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\$\begingroup\$ @user1430508: We'll be selling the product commercially; I considered Gumstix like I would any other part like an IC or resistor. But your question is entirely valid - I'm now going to go and check the T&Cs very carefully. Just in case :-) \$\endgroup\$– carveoneJul 21, 2013 at 13:32
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\$\begingroup\$ okay, do comment back if you get a red flag for commercial use of Gumstix in the T&Cs :) \$\endgroup\$ Jul 21, 2013 at 13:51