On 26/06/2020 15:24, Ahem A Rivet's Shot wrote:
> On Fri, 26 Jun 2020 14:30:33 +0100
> David Higton  wrote:
>
>> As for PCB traces: I discovered in the early 1990s, when we were
>> using 74ABT logic devices, which have nanosecond rise and fall times,
>
>  Around 1980 two of us assembled wire-wrap prototype memory boards
> (stuffed with 2kx8 SRAM and 74LS logic) the other guy was an experienced
> wireman who made a lovely job of it, the looms of address and data bus were
> really clear. I was a student and not so inclined to making things pretty,
> every wire made the correct connection but they went all over the place in
> a rat's nest. On first sight the boss commented that his was the way it
> should be and I needed to do better - fair enough I thought - his was
> pretty.
>
>  Both boards passed a DC buzz test (every wire going where it should
> be and no extras) and a power on smoke test and so were duly populated with
> components and tested. Mine worked first time - his radiated at ~30MHz
> strongly enough to be picked up by an open scope probe across the room
> purely because of the way the wires were laid out on the board (it didn't
> work of course) - he wound up hanging terminating resistors at the end of
> the bus loops to shut it up, mine didn't need them.
>
>  Wire wrap looms can behave like transmission lines too.
>
>  We all learned something that day - including the boss.
>

Yep I've seen the same, a so called professional wireman formed the
wirewrap wires into neatly tied together bundles for address, data etc.
Didn't work, and it was only running at about 1MHz too!

--
Brian Gregory (in England).

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