How to fabricate on copper clad CPU, RAM, ROM. On a primitive level.

Discussion in 'Digital Circuit Design' started by Zerokill, Sep 11, 2016.

  1. Zerokill

    Thread Starter New Member

    Dec 10, 2015
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    What I want to do is build an early stage pc that ran like dos operating system. I know I can print my circuit out and iorn on copper clad and acid etch circuit and make in limited to few hundred transistors for all my components. but wonder how to link transistors to form latches into memory, and an ALU, shift registers, etc. How to programe simple operator system and map ask2 codes for a keyboard and basic math and to make a basic write tool like notepad.
     
  2. absf

    Senior Member

    Dec 29, 2010
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    I have seen people making 555 and 741 using transistors.

    But just making a 8088 using transistors is no trivial matter. It would take thousands of BJT or mosfet to make a working 8088 CPU.

    May be you can just get a working old 8088 from some junk PC board and find some TTL chips like latches, bi-directional buffers, SRAM and Eproms and make the simplest 8088 computer. That I think should be doable.... Just my 2 cents.

    Allen
     
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  3. be80be

    Senior Member

    Jul 5, 2008
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  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    We built simple computer in Navy C school.
    It was pitiful. We input 10 numbers that represented grades (90,89,75,95 etc.) and program to get an average.

    Memory was 4k and program used little more than half.

    Took us a full month to do so, and it was IC based. Doing it via individual transistors is simply insane.
     
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  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Check out the transistor clock. It is a very simple circuit compared to even a 4-bit computer, but it contains 194 transistors, 566 diodes and 400 resistors. You can see towards the end of the manual the description of how logic gates and latches are done on a transistor level (RTL logic). http://www.transistorclock.com/tranmanual.pdf

    Here you can find the schematic of intel 4004 processor http://www.4004.com/
     
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  6. hp1729

    Well-Known Member

    Nov 23, 2015
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    "Few hundred transistors"? Many 100,000 transistors!
    The very early Intel 4004 used about 2,300 transistors., and that would be just the CPU, without any memory or I/O.
    You could build a computer out of TTL or CMOS logic gates but that would take up about 5 to 10 square feet of PC board space.
    I have worked on computers made just of transistor circuitry and they take up the space of a refrigerator. :) Search on "Univac 1212".
     
    Last edited: Sep 12, 2016
  7. RichardO

    Well-Known Member

    May 4, 2013
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  8. hp1729

    Well-Known Member

    Nov 23, 2015
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    Outrageous! And that is just the "functional part" of the 6502? The ALU only? No memory included? No I/O?
     
  9. absf

    Senior Member

    Dec 29, 2010
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    The original MOS6502 chip has 3910 transistors and the Intel8088 has 29000 transistors.... here

    If the 8088 is made the same way as the Monster6502, it will need a board space 7 times bigger.:p:D

    Why did the WDC65C02 need 11,500 transistors is beyond me?

    Allen
     
  10. RichardO

    Well-Known Member

    May 4, 2013
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    The 6502 is a microprocessor. It has the clock generator, instruction decode and sequencer, program counter, ALU, working registers (accumulator, X and Y index registers, stack pointer), status register, interrupt control, address and data buffers.

    No memory except for (maybe) ROM storing the microcode. You need to take a step up to a microcontroller to get fancy I/O functions and program and data memory.

    See here for a block diagram:
    http://www.devili.iki.fi/Computers/Commodore/C1581/Service_Manual/Page_05b.gif


    p.s. I was told that to make an 8008 microprocessor (Intel's predecessor to the 8080) into a "computer" needed about 25 chips. At that time there were no bus-wide buffers or latches. There were 6-bit parts but no 8-bit parts.
     
  11. RichardO

    Well-Known Member

    May 4, 2013
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    The lowly 8008 had 3500 transistors according to your reference. The 6502 designers were _really_ stingy with their resources. :eek:
    For instance, the address register was output only, not tri-state.

    One reason the WDC65C02 has more transistors is that it is a CMOS part, not NMOS. I am not sure if the 6502 had active pullups that used transistors instead of resistors.

    p.s. Your reference says 3510, not 3910, transistors for the 6502 -- only 10 more than the 8008.
     
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