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Notes on MSI/88e Deconstruction

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  • Mark Graybill
    Well, I pulled the ROM out of the MSI/88e today and wasn t able to read it with any of the 8Kx8 formats my ROM burner will read. The address and data lines
    Message 1 of 3 , Jun 5, 2003
      Well, I pulled the ROM out of the MSI/88e today and wasn't able to read it
      with any of the 8Kx8 formats my ROM burner will read. The address and data
      lines look like a standard layout, but I haven't traced the select logic on
      the board yet to see what's going on. It's pretty easy to follow, though,
      since it's on the same board as the CPU and right next to it.

      The chip appears to be a Signetics 27884, which I don't have data for. But
      since the address and data lines looked standard, I thought I'd drop it in
      the reader and give it a try. If anyone's got a suggestion for reading this
      chip, let me know. If I can figure out the select logic I may put together
      an adapter to allow the reader to treat it as a 2764.

      In the meanwhile, I'm going to check out the 1802 I pulled as well. If time
      permits around my other projects, I'll try to do a quick free-run test with
      it this afternoon.

      A note to people thinking about using the MSI/88e for parts--the assemblers
      were very good about trimming the leads on the chips, so the leads are too
      short for many types of sockets and for breadboards. Low profile sockets
      will hold onto them pretty well, but you may want to include something to
      hold the chip down to keep it from lifting out, even then. If you're doing
      wire wrap you'd probably have to put the chip in a low-profile socket then
      put that socket in a wire wrap socket, and have something to hold the chip
      down since if the socket flexes or gets jarred sharply the chip can fall
      out.

      Of course, if you're confident enough to solder the chip straight into the
      circuit, this won't be a problem. Presently I'm not that confident. (Now
      where did I put that lead stretcher?)

      -Mark G.
    • J.C. Wren
      Why not just solder the chip to a machine tool pin socket, and insert that into another socket? (You *are* using machine tool pin sockets, right? Anything
      Message 2 of 3 , Jun 5, 2003
        Why not just solder the chip to a machine tool pin socket, and insert that
        into another socket? (You *are* using machine tool pin sockets, right?
        Anything else would be sub-standard!)

        --John

        On Thursday 05 June 2003 17:10 pm, Mark Graybill wrote:
        > Well, I pulled the ROM out of the MSI/88e today and wasn't able to read it
        > with any of the 8Kx8 formats my ROM burner will read. The address and data
        > lines look like a standard layout, but I haven't traced the select logic
        > on the board yet to see what's going on. It's pretty easy to follow,
        > though, since it's on the same board as the CPU and right next to it.
        >
        > The chip appears to be a Signetics 27884, which I don't have data for. But
        > since the address and data lines looked standard, I thought I'd drop it in
        > the reader and give it a try. If anyone's got a suggestion for reading
        > this chip, let me know. If I can figure out the select logic I may put
        > together an adapter to allow the reader to treat it as a 2764.
        >
        > In the meanwhile, I'm going to check out the 1802 I pulled as well. If
        > time permits around my other projects, I'll try to do a quick free-run test
        > with it this afternoon.
        >
        > A note to people thinking about using the MSI/88e for parts--the
        > assemblers were very good about trimming the leads on the chips, so the
        > leads are too short for many types of sockets and for breadboards. Low
        > profile sockets will hold onto them pretty well, but you may want to
        > include something to hold the chip down to keep it from lifting out, even
        > then. If you're doing wire wrap you'd probably have to put the chip in a
        > low-profile socket then put that socket in a wire wrap socket, and have
        > something to hold the chip down since if the socket flexes or gets jarred
        > sharply the chip can fall out.
        >
        > Of course, if you're confident enough to solder the chip straight into the
        > circuit, this won't be a problem. Presently I'm not that confident. (Now
        > where did I put that lead stretcher?)
        >
        > -Mark G.
        >
        >
        >
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      • erd_6502
        ... For some parts, that s not cost-effective. Fortunately for me, I picked up a few tubes of 14-pin machine-pin sockets at the Dayton Hamvention last month
        Message 3 of 3 , Jun 6, 2003
          --- In cosmacelf@yahoogroups.com, "J.C. Wren" <jcwren@j...> wrote:
          > Why not just solder the chip to a machine tool pin socket, and
          > insert that into another socket?

          For some parts, that's not cost-effective. Fortunately for me, I
          picked up a few tubes of 14-pin machine-pin sockets at the Dayton
          Hamvention last month for $1/tube (that's $0.04/socket)... I
          probably should have bought the entire bin! Normally, they are
          several times more expensive than that. New CMOS parts are
          frequently cheaper, CPUs, RAM and odd I/O chips notwithstanding.

          > (You *are* using machine tool pin sockets, right?
          > Anything else would be sub-standard!)

          Absolutely. Somewhere in the attic, I have a couple of cubic
          feet of machine-pin WW sockets. All I need is a good source
          of WW wire and I'm all set.

          -ethan
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