[TUHS] 2.10

Noel Chiappa jnc at mercury.lcs.mit.edu
Sat Nov 22 01:37:53 AEST 2014

    > From: Clem Cole <clemc at ccc.com>

    > an old Able "Enable" board which will allow you to put 4Megs of memory
    > in an 40 class processor (you get a cache plus a new memory MAP with 22
    > bits of address like the 45 class processors).

But it doesn't add I/D to a machine without it, though, right? (I tried
looking for Enable documentation online, couldn't find any. Does anyone know
of any?)

I recall at MIT we had a board we added to our 11/45 which added a cache, and
the ability to have more than 256KB of memory, but I am unable to remember
much more about it (e.g. who made it, or what it was called) - it must have
been one of these.

I recall we had to set up the various memory maps inside the CPU to
permanently point to various ranges of UNIBUS address space (so that, e.g.
User I space was assigned 400000-577777), and then the memory map inside the
board mapped those out to the full 4MB space; the code changes were (IIRC)
restricted to m45.s; for the rest of the code, we just redefined UISA0 to
point to the one on the added board, etc. And the board had a UNIBUS map to
allow UNIBUS devices access to all of real memory, just like on an 11/70.

    > From: Jacob Ritorto <jacob.ritorto at gmail.com>

    > So does that single board contain the memory and everything, or is this
    > a backplane mod/special memory kind of setup?

I honestly don't recall much about how the board we had at MIT worked, but i)
the memory was not on the board itself, and ii) there had to be some kind of
special arrangements for the memory, since the stock UNIBUS only has 18 bits
of address space. IIRC, the thing we had could use standard Extended UNIBUS
memory cards.

I don't recall how the mapping board got access to the memory - whether the
whole works came with a small custom backplane which one stuck between the
CPU and the rest of the system, and into which the new board and the EUB
memory got plugged, or what. I had _thought_ it somehow used the FastBUS
provision in the 11/45 backplane for high-speed memory (since with the board
in, the machine had a basic instruction time of 300nsec if you hit the cache,
just like an 11/70), and plugged in there somewhere, but maybe not, since
apparently this board you have is for a /34? Or maybe there were two
different models, one for the /45 and one for the /34?

    > With the enable34 board, do I have some hope of getting 2.11bsd on this
    > one?

Since I doubt it adds I/D to machines that don't already have it, I would
guess no. Unless somehow one can use overlays, etc, to fit 2.11 into 56KB of
address space (note, not 'memory').

    > I do have an 11/73 I'm working on that could run that build much more
    > easily and appropriately..

That's where I'd go.

I do have that MIT V6 Unix with TCP/IP, where the TCP is almost entirely in
user space (only incoming packet demux, etc is in the kernel), and I have
found backup tapes for it, which are off at an old tape specialist being
read, and the interim reports on readability are good, but until that
happens, I'm not sure we'll be seeing TCP/IP on non-split-I/D machines.


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