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Re: Serial ports required in small systems

Greg Forsythe wrote:
What number of Accu-Votes will a second serial card added to a Personal Computer (to provide 4 upload lines with modems), support without causing GEMS problems?
  That depends on what serial card you use and how many interrupt vectors you have to use for the serial ports.  Normally PC's reserve interupts 3 and 4 for COM ports 2 and 1 respectively.  You can share these interrupts with COM 1 and 3 sharing IRQ 4 and COM 2 and 4 sharing IRQ 3 but you can only use one COM port per IRQ at any one time (i.e. you can switch between COM 1 and 3 but not use both at once).

  However, many add-on serial boards will give you an additional 1 to 4 ports and allow you to select any IRQ for each.  Using these you can add as many ports as you have unused IRQs.  WinNT will allow you to add additional COM ports using these IRQs.

  If you need still more ports, you need to go to a "smart" multi-port card such as the DigiBoards.  These provide from 8 to 64 serial ports sharing a single IRQ.  Using multiple smart multi-port cards you could in theory support hundreds of serial ports on one computer.

  GEMS can use whatever serial ports are set up in WinNT and I believe that we have used about 20 ports on some systems.