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From: stever@videovax.UUCP
Newsgroups: comp.sys.amiga
Subject: Grounding of high-speed logic
Message-ID: <4226@videovax.Tek.COM>
Date: Sat, 14-Feb-87 15:51:02 EST
Article-I.D.: videovax.4226
Posted: Sat Feb 14 15:51:02 1987
Date-Received: Sun, 15-Feb-87 09:10:16 EST
References: <2438@jade.BERKELEY.EDU> <1375@cbmvax.cbmvax.cbm.UUCP> <7@ethz.UUCP>
Reply-To: stever@videovax.Tek.COM (Steven E. Rice, P.E.)
Organization: Tektronix Television Systems, Beaverton, Oregon
Lines: 21
Summary: Agnus undoubtedly needs both those grounds!

In article <7@ethz.UUCP>, Claudio Nieder (claudio@ethz.UUCP) writes:

> . . .

> According to the AGNUS PIN ASSIGNMENT printed on page C-2 of the Amiga
> Hardware Reference Manual Agnus has two VSS pins (27,41). Is there
> really no way to use one of these to add an additional address line ?

High-speed logic needs solid grounding to avoid all sorts of problems.
An example of this is the 68020 processor, which has *13* ground pins
(and 9 Vcc pins)!  If you are switching eight or ten outputs (to say
nothing of 64+), the inductance of the ground pin and the lead inside
the package can develop more than a volt drop during output transitions.
This kind of voltage drop across the "ground" raises havoc with logic!

Agnus undoubtedly needs both those grounds. . .

					Steve Rice

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