[HECnet] No connectivity to arsgea 4

[David Moylan]

Reminds me a little of the hardware development of the BBC Micro. The original design used an NS 81LS95 multiplexer for the memory, and for reasons that nobody could explain, only the NS component worked in their design - the same component from other vendors failed.

The core reason was due to the bus speed and how the original infrastructure design was done, but the choice of many components was critical to the stability of the machine.

I'm not implying NS is better - just saying that it's interesting to compare stability and long term failure rates in the field and how much they can vary.

Cheers, Wiz!!


> -----Original Message-----
> From: owner-hecnet at Update.UU.SE [mailto:owner-
> hecnet at Update.UU.SE] On Behalf Of Dave McGuire
> Sent: Sunday, 24 January 2021 5:23 AM
> To: hecnet at Update.UU.SE
> Subject: Re: [HECnet] No connectivity to arsgea 4
> 
> On 1/23/21 12:48 PM, Johnny Billquist wrote:
> > Speaking of things like 74-series stuff. Based on various restoration
> > projects I'm aware of, there seems to be a huge difference in quality of
> > those ICs. Depending on manufacturing batch, and manufacturer...
> >
> > Some never fail, while with some others, you can almost predict that
> > they will be non-functional now.
> >
> > So I guess it also do depend a bit on who you picked as supplier back in
> > the day.
> 
>    Yes, very much so.  We've noticed that National Semiconductor is the
> worst offender for actual IC failures, and Texas Instruments is the
> worst for corrosion on IC leads.
> 
>               -Dave
> 
> --
> Dave McGuire, AK4HZ
> New Kensington, PA