[ih] Intel 4004 vs the IMP

[Steve Crocker]

I believe the first batch of IMPs were capable of handling up to four hosts
and up to four 50kbs communication lines, but the total was limited to 7.
The limitation of 7 interfaces was due to the physical slots inside the
machine, not a bandwidth limitation.

And, yes, the communication lines were 50 kbs using Western Electric 303A
modems.  The modem sprayed the data across 12 twelve(!) voice grade analog
lines.  Digital communication lines came along later.

Steve


On Mon, Nov 15, 2021 at 10:00 PM Jorge Amodio <jmamodio at gmail.com> wrote:

>
> Weren't the BBN modems capable of handling up to 6 "phone lines" at
> 50,000bps. So basically analog dedicated phone lines.
>
> I'm sure the early lines were not DDS 56K
>
> Regards
> Jorge
>
>
> On Mon, Nov 15, 2021 at 8:35 PM Steve Crocker via Internet-history <
> internet-history at elists.isoc.org> wrote:
>
>> Arpanet lines were 50 kbs, not 56 kbs.
>>
>> Sent from my iPhone
>>
>> > On Nov 15, 2021, at 9:11 PM, Timothy J. Salo via Internet-history <
>> internet-history at elists.isoc.org> wrote:
>> >
>> > I think we all agree that the IMP was a pretty limited machine.  From
>> > the backup slides of a presentation of mine:
>> >
>> > Early ARPANET router, Interface Message Processor (IMP), (1969):
>> > o 16-bit words, 12-16 K-word memory
>> > o 100-μsec clock (10 KHz)
>> > o Early ARPANET links: 56 kbps
>> > o 0.18 clock cycles per bit
>> >
>> > I have argued that this, 12-16 K words of memory, is why we had the
>> > end-to-end argument (which morphed into a principal and then into a
>> > canon).
>> >
>> > (The rest of the presentation pretty much ignores the end-to-end
>> > argument.)
>> >
>> > Also from this presentation:
>> >
>> > Early NSFNET router: DEC LSI-11/73 (1983) with Fuzzball router
>> > o 512 KB memory
>> > o (15.2 MHz)
>> > o 271 clock cycles/bit
>> >
>> > -tjs
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>