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34461Re: [midatlanticretro] MARCH's 11/44

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  • Dave McGuire
    Feb 17, 2014
      On 02/17/2014 10:33 AM, David Riley wrote:
      >> Yeah. When you're at the ">>>" prompt, you're interacting with
      >> firmware running on an 8085 that has direct access to parts of the
      >> PDP-11/44's internal CPU bus, as well as the Unibus. That 8085 has 4KB
      >> of ROM and 256 bytes of RAM, on a very crowded board, and with all the
      >> bus control stuff going on, they'd have been hard-pressed to get much
      >> more functionality out of that.
      > Yup. We did get it to boot Unix successfully off of Matthew's Emulex
      > SCSI card, but that's back with him now. There are RL drives with the
      > machine (I think their cables are even still attached), but I don't
      > think they're in the rack. There's an RA60 which we didn't have any
      > media to test with (and any of the other RA drives were tripping the
      > breaker on the generator as soon as we powered them up; we need a
      > fatter power feed for this machine).

      Be careful with that RA60...don't just fire it up. Check (and
      probably clean) the heads first)

      > Theoretically, one of the RA drives might be bootable. However, my
      > recollection is that it's an RA80 and an RA92, so they may be a bit
      > balky even if we could keep them on without tripping breakers.

      The RA80 and RA92 aren't even in the same league...The RA92 is a much
      MUCH later drive, and is very reliable. It's the RA90 that had lots of
      problems. The RA92 pulls very little power. I'll see about measuring
      one at some point soon, but I'd be surprised if it were more than 200W
      real-world. If you're popping breakers with an RA92, something is wrong.

      The best bet to get it running quickly would be to have someone
      (probably Matt) bring that RA92 up here. We'll plug it into my
      media-mecca machine and write an image to it. (and make an image of
      what's there if desired)


      Dave McGuire, AK4HZ
      New Kensington, PA
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