Date   : Tue, 26 Oct 2010 17:08:07 +0100
From   : philpem@... (Philip Pemberton)
Subject: Reversing the Tube ULA (destructively)

On Tue, 2010-10-26 at 15:52 +0100, Mark Haysman wrote:
> There is a third chip, made by AMS
> 
> http://www.retroclinic.com/misc/tubechips.jpg
> 
> It maybe a cousin of the AMI one, as both come from Austria it seems. I've 
> also not seen the one on the daughterboard, do you have a pic?

That AMI chip was probably made by AMI Semiconductor, now part of
ONSemiconductor. They started out marking their chips "AMI", then
changed to "AMIS".

The AMS chip was made by Austria Mikro Systeme, now austriamicrosystems.

This is not entirely surprising -- back in the early 80s, AMI and AMS
were running the fab plants as a joint-venture. In 1987, AMI and AMS
split, leaving the American fabs under the control of AMIS and the
European fabs under AMS's control. It was probably easier for AMS to
handle the European customer base, and leave AMI to deal with American
customers.

In any case, the photomasks would have been at the AMI Austria fab.
Rather than move them and risk them getting damaged, it was probably
MUCH easier for AMI to leave them with AMS, and for Acorn to place
future parts orders through AMS.

Inside the plastic, it's probably the exact same chip, right down to any
logos or ID markings. Once you make a mask set for an IC, you DO NOT
change it unless there's something wrong with it. Too much risk -- "if
it ain't broke, don't try and fix it!"

-- 
Phil.
philpem@...          
http://www.philpem.me.uk/