Loading ...
Sorry, an error occurred while loading the content.

31479Re: [midatlanticretro] VAX 780 vs. 750

Expand Messages
  • Dave McGuire
    Jul 1, 2013
    • 0 Attachment
      On 07/01/2013 02:41 PM, David Riley wrote:
      > The 11/750 was a smaller, slower, cost-reduced version of the 11/780. The
      > 11/730 (even later), was a smaller, even slower, further cost-reduced version
      > of the same. My recollection is that most of the size and cost reduction was
      > accomplished by using more highly integrated gate arrays to replace discrete
      > TTL logic chips (which, at the time, were faster than the gate arrays).
      >
      > I believe the 11/730 was small enough to be easily rack-mountable, while the
      > 11/750 occupies most of a short cabinet. I could be misremembering, though;
      > I've never actually seen any in the flesh (part of why I'm excited for the
      > workshop).

      The 11/730's implementation of the VAX instruction set is more
      heavily based in microcode than that of the 11/750, making it much
      smaller and much slower. Basically fewer and fewer functions
      implemented in hardware, more and more functions implemented in microcode.

      The 11/730 CPU is built from Am2901 bit-slice chips. The control
      store (where microcode lives) is actually RAM, so when the 11/730 is
      powered up, it doesn't speak the VAX instruction set. Microcode is
      loaded from a TU58 tape cartridge into the control store by an
      8085-based service processor within the machine.

      Most 11/730 CPUs are in BA11-K style chassis, VERY compact by VAX
      standards of the day. Standard 19" rackmount.

      The VAX-11/725 is an 11/730 repackaged into a roll-around deskside
      chassis. The VAX-11/751 is a repackaged 11/750 that can be mounted in a
      standard 19" rack. The 751 was targeted at embedded and OEM applications.

      -Dave

      --
      Dave McGuire, AK4HZ
      New Kensington, PA
    • Show all 14 messages in this topic