Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: A2000, B2000, what's the DEAL!???
Keywords: Revisions, A2000, B2000...etc etc...
Message-ID: <16011@cbmvax.commodore.com>
Date: 21 Nov 90 14:19:54 GMT
References: <15706@brahms.udel.edu> <328@rusux1.rus.uni-stuttgart.de>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 54

In article <328@rusux1.rus.uni-stuttgart.de> ps3@ph3hp840.physik.uni-stuttgart.de (ps-Gruppe) writes:

>Once upon a time there was a Amiga 1000 and a sidecar. And Commodore said
>'We should put the sidecar inside the Computer'. And so Commodore in
>Braunschweig (Germany) has built the A2000 and the XT-Card. The A2000 is
>quite similar to the A1000, they just added the slots and 512 kB Ram
>instead of 256 kB. So they managed to produce a Amiga with a XT inside
>in a short time.

That's basically the right idea.  What's called the A2000b, or B2000, or
(our official original name) the A2000-CR, was originally a started as a
cost reduction of the German design.  The A2000a was based on the A1000 chips;
thin Agnus and lots of PALs and buffers, coupled with a backplane based on the
original backplane specifications done in Los Gatos.  The A2000b borrowed 
instead from the A500 design, with Fat Agnus.  I designed the thin Buster chip
to replace the PAL logic used for the backplane and to add the "Coprocessor
interface" that made possible the A2500 bundled systems.

>Later Commodore developed the B2000, which has several differences in Hardware:

>- The keyboard sometimes have problems with the first sign you type in. This
>  problem can be solved by removing a condensator. Furthermore some versions
>  of the AT-Emulator (the software -- not the AT-Board) do not run with the
>  B2000, if the wrong version of keyboard is used.

The real problem, of which you see two symptoms here, was based on the fact
that there were two different keyboard designs.  The original, which used
a rather large design based on some buffer chips and an Intel CPU, is 
responsible for the problems with some software.  It is very close to the limit
of the published keyboard specifications, and some programs that drive the
keyboard directly, rather than go through the input.device or Intuition or
whatever, ignored the specs.  That's a problem with this keyboard on the A2000a
or A2000b, or for that matter the A1000 if you hooked one of these keyboards
up to the A1000 via an adaptor cable.  This keyboard can be identified by the
smaller function keys -- they're the same size as the "Esc" key.  All A2000as 
and a few A2000bs shipped with this keyboard.  We switched over to the newer
one, which was internally based on a MOS 6500/1 like the A1000 keyboard, soon
after the A2000b was in production.  This keyboard's function keys are the
size of the "Alt" keys.  The "miss the first character" problem is based on 
some drive differences between the two keyboards.  The original keyboard had
big buffer chips, which made it electrically noisy.  To solve this noise
problem, A2000bs were outfitted with an extra set of bypass capacitors at
the keyboard connector.  When the new keyboard came along, these caps were a
bit too much for it, only it took some time before anyone noticed there was
a missing character problem.  Eliminating the additional caps, restoring the
original design, solves the problem.

>Thomas Stuempfig             |  ocac@ds0rus1i.bitnet


-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
	Standing on the shoulders of giants leaves me cold	-REM