Looking for fast transistors to build own cmos logic.

Discussion in 'Digital Circuit Design' started by Paul Griffiths, Nov 21, 2017.

  1. Paul Griffiths

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    Nov 21, 2017
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  2. dl324

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    Welcome to AAC!

    What do you plan to do with this high speed discrete CMOS logic?

    You're asking for nothing but trouble. You're going to have problems with device matching and parasitics from interconnects.
     
  3. BobTPH

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    Jun 5, 2013
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    AT 45GHz, the maximum distance a signal can go in one clock cycle is 0.66 cm. I hope what you are building is small.

    In ICs that function at 1/10 this speed, clock skew and speed of light delays of signals is a significant problem. With discrete logic it would be a non-starter.

    Bob
     
  4. Paul Griffiths

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    Nov 21, 2017
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    Well, I'm hoping to dabble in processor designs.
    I want to use fast components as saving on ordering extra.
    Any advice?
     
  5. crutschow

    Expert

    Mar 14, 2008
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    CMOS digital IC's will be a lot cheaper, faster, and use many fewer parts than you can build using discrete transistors.
    Why do you want to use transistors instead of IC's?
    You will end up with hundreds if not thousands of transistors to build a processor. :eek:
     
  6. Paul Griffiths

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    Nov 21, 2017
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    As yet to know everything but believe may save count as some transistors may be used for a few logic math than ic's that can't get to each transistor.
     
  7. Papabravo

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    This is essentially a non-starter. What you want to do is design a processor to be implemented in an FPGA. You'll do the design in Verilog or VHDL and synthesize it inside a single chip. There is NO OTHER PRACTICAL way to do this.
     
  8. Paul Griffiths

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    Nov 21, 2017
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    FPGA's not fast due to the programming logic's.
     
  9. dl324

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    The way the Big Boys do this is they have simulators that are set up for the target process. You draw the circuit, run parasitic extraction, and simulate circuit performance. Once the circuit is fabricated, you try to find out why it doesn't perform as expected. That's what we did for microprocessors that had hundreds of millions of transistors *before* the process was anywhere near production worthy.

    The last design I'm aware of that did an actual breadboard was the 80286. I knew a technician who worked on it.
     
  10. Papabravo

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    This is total nonsense. Once the device is programmed, the programming logic has no further effect.
     
  11. RichardO

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    May 4, 2013
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    Sinus23, Sensacell, absf and 2 others like this.
  12. Paul Griffiths

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    Nov 21, 2017
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    So, the logic flow is produced by nonsense?
     
    Papabravo likes this.
  13. Paul Griffiths

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    Nov 21, 2017
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  14. Papabravo

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    Does anybody except Paul know what he is referring to?
     
  15. Paul Griffiths

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    Nov 21, 2017
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    Each connected gate requires a programmed part which slows down it's entirety. All part of the game...
    Or do you believe there's an intel engineer inside with a soldering iron?
     
  16. Papabravo

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    This is cool project, but at less than 1/10 speed is mainly a tour-de-force to show it can be done. We did such things with Xilinx chips to simulate custom communication ASICS back in the 1990's. Clock recovery for Manchester encoded data ran at 1/10 th speed using 110 FAST IC's (74F series) and PALS. The rest of the chip was in 56 XC4000 series FPGAs all daisy chained together for programming. The power up delay for the programming was hardly noticeable. The 1st silicon of the part worked as expected and went directly into production.
     
  17. JohnInTX

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    Jun 26, 2012
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    @Paul Griffiths
    You are a long way from transistors here. Where are you going with all of this?
     
  18. hrs

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    Jun 13, 2014
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    I speculate a BBC Micro and a line of BASIC.
     
  19. absf

    Senior Member

    Dec 29, 2010
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    It is the BASIC statement used in BBC BASIC:

     
  20. Papabravo

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    I had a BBC model B:
    SOUND 10, -15, 128, 1000


    It has been a long time (maybe half a century) since I had any need for BASIC, so excuse me for not recognizing it or understanding it's significance to the discussion, which was building a computer out of discrete transistors. As the designers of the MONSTER 6502 pointed out you cannot buy the discrete transistors such a design requires, and you can't do anything about the massive amount of gate capacitance you need to overcome.
     
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