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[ih] NCP and TCP implementations
Ah. And other memories are slowly coming back. In 1981 I joined The
Aerospace Corporation to establish a computer science research lab. There
was an IMP at the Air Force operation across the street, and I arranged to
get our lab attached to it. When it came time to register our host name, I
used "Aerospace" as the long name but I was challenged to find a good short
name. The official name of the corporation was "The Aerospace Corporation"
and it was not uncommon to see "TAC" used internally. But that would have
caused massive confusion.
What actually happened was even more interested. I decided to register
just the letter A. It took Carnegie-Mellon University off the net. They
had several hosts, CMU-A, CMU-B, etc, and the were using single letters
internally as abbreviations. Their A machine was the gateway to the
Arpanet. In short order, single letter host names were prohibited from the
On Tue, Mar 10, 2020 at 2:38 PM Bob Hinden <bob.hinden at gmail.com> wrote:
> H Steve,
> > On Mar 10, 2020, at 11:03 AM, Steve Crocker via Internet-history <
> internet-history at elists.isoc.org> wrote:
> > Argh. I echoed Leo's use of "TAC." I read it as referring to the TIP.
> > I recall correctly, the "TAC" was an access control method on the TIPs.
> > "TIP Access Control" I think.
> The Terminal Access Controller (TAC) was a TIP like machine that ran
> TCP/IP instead of NCP. I think it was done for the DDN, but my memory on
> that part is hazy.
> > Steve
> > On Tue, Mar 10, 2020 at 1:55 PM Bernie Cosell via Internet-history <
> > internet-history at elists.isoc.org> wrote:
> >> On 10 Mar 2020 at 13:23, Steve Crocker via Internet-hi wrote:
> >>> The TAC was an extension of the IMP. The original IMP was built on
> >>> the
> >>> Honeywell 516 (and later 316) platform, which was a 16 bit twos
> >>> complement
> >>> computer. I assume Hinden's reference to 15-bit arithmetic reflected
> >>> the
> >>> fact that the arithmetic was signed.
> >> I honestly cannot remember what the TAC was!! Was that the TIP?
> >> Regardless,
> >> yes, the x16s had 16-bit signed arithmetic with 10 bit addressing 9 bits
> >> of page
> >> address, 1 bit of "this page" or the 0 page, 16Kwords of memory.
> >> Things got more complicated with the 316 -- it supported 32K words.
> >> we
> >> did for the TIP [and maybe the TAC, whatever that was] was to keep the
> >> *unchanged* in the bottom 16K, and then in the upper 16K we wrote a
> >> self-contained "host". There was some [small!] hack to fake interrupts
> >> input/output to this host but to the IMP it thought it was just another
> >> NCP
> >> connected host. It'd set up a host output buffer and instead of doing a
> >> hardware
> >> "send" it'd pass control to the upper 16K. Similarly [at least for the
> >> TIP], when it
> >> got something in from a terminal it'd copy it into a host-input buffer
> >> then
> >> issue an "interrupt" down to the IMP. Worked quite well.
> >> /Bernie\
> >> Bernie Cosell
> >> bernie at fantasyfarm.com
> >> -- Too many people; too few sheep --
> >> --
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