3 megabit ethernet

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Does anyone here know about 3 megabit ethernet?

Do any such chips still exist?

Or maybe an FPGA based bridge to 10 megabit would be the easiest
way to do the conversion.

-- glen

Re: 3 megabit ethernet
On Tue, 31 Mar 2015, in the Usenet newsgroup comp.dcom.lans.ethernet, in article

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Haven't seen any since....  1996?

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It's getting AWFULLY close to the first of the month...  but what the
hell!

I haven't seen (Motorola) 10000 series ECL chips for sale in YEARS, but
I honestly can't recall if they were used in the 3 MHz version or just
10Base5 reference implementations.  Given we're talking 1976, I vaguely
recall most of the circuit was discretes.   Hey, at least it wasn't
vacuum tubes.

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Why?   Sneaker-net would be faster to implement.  (yes, I do have a box
of 8" floppies as well as several boxes of 5.25s).

        Old guy

Re: 3 megabit ethernet
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No, it is actually for an Alto.
  
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I think they don't have floppy drives on them.  

-- glen

Re: 3 megabit ethernet
On Wed, 1 Apr 2015, in the Usenet newsgroup comp.dcom.lans.ethernet, in article

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Never worked on one, but my understanding was that the chips used were
"ordinary" 74 series TTL.  The 74164 (S->P) and 74165 (P->S) were 8 bit
parallel shift-registers.   The line driver and receiver were discretes.

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What are you actually trying to do?

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Alto - correct, the hard disk cartridges were removable.  I was thinking
of the more "modern" DLion, which did have an 8 inch drive.  We had a
number of them, and at least one had both 10 and 3 MHz interfaces, which
was used as a limited capability router.  

        Old guy

Re: 3 megabit ethernet
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Someone else is actually trying to do it, which is connect an Alto
to modern ethernet. I believe the reason is to use it for network
based disk storage.  

One possibility would be to create a bridge between 3Mb and 10Mb
ethernet.  Another would be to adapt a 10Mb to the Alto I/O bus,
such that it could talk to it like it was 3Mb.   (Yes, I know that 3Mb
has 8 bit addresses.)

Thanks.

-- glen

Re: 3 megabit ethernet
On Wed, 1 Apr 2015, in the Usenet newsgroup comp.dcom.lans.ethernet, in article


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Didn't think there were any outside of museums

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I'd assume you mean having an outside box act as a network disk for the
Alto -  the other way 'round makes no sense, as the Alto disks were
something like two or three megabytes.

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about the only solution

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Never worked on the hardware, but my impression is that the interface was
CPU bandwidth limited - and can't service interrupts much faster than the
3 Mb demanded.

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The bridge device (actually a gateway) handles that.

        Old guy

Re: 3 megabit ethernet

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It is in a museum, but it is supposed to work.
  
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Yes.  

I don't know the details, but it seems that the disks don't
work very well.
  
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Well, it could also be a router.  There probably won't be much else
on the net, so it probably doesn't matter much either way.
  
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That is fine. At some point, most devices couldn't handle interrupts
as fast as 10Mb/s ethernet could generate them, but most of the time
they didn't have to.  
  
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Yes.  

I just put that in, in case someone thought about mentioning it.

-- glen


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