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12876Re: [midatlanticretro] Re: makeshift IBM monitor

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  • B Degnan
    Jun 1, 2009
    • 0 Attachment
      U33
      MK36C35N-4
      1501476
      ZA
      (copyright) IBM CORP
      1981, 1983
      D Malaysia

      Tells you it's a 2nd REV16K-64K (upgraded) ROM set.  The first rev did not have a routine for using hard drives, and some other things so most people upgraded the ROMS so they could use newer parts and memory.



      Here's as much info as I can pull off the mainboard

      Machine Serial:
      0177038
      this year I worked on the following other 16-64K boards, so yours is right in there among them, definitely an original, probably from late 1981 early 1983.:

      0159618
      0239462
      0192592 (MARCH's with original ROMS)

      On the planar:

      SW1
      on on on on off on on off

      SW2
      on off on on off off off off


      you have a full complement of RAM (64K) on the motherboard. 

      I assume you have SW1 reversed.  Up means "on" if facing from the front looking down. 
      If you have a co-processor, two drives, CGA monitor then SW1 should be: [off on -- -- on off off on] (where pertains to RAM).

      If SW1's 5 is up and 6 down  - that means CGA display.  Monochrome 5 and 6 are down.  Never mix and match without first changing the switches before powering on.  Otherwise you will fry the board and short the system.

      Math co-processor 2 = up/on.

      In a nutshell it looks like you have a standard configuration, no changes needed assuming you use a CGA monitor.  Don't try to use monochrome with these settings.  Someone did that to MARCH's 5150, and we had to replace the display card as a result. 

      Hope this helps.

      Bill

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