From: barrett@iastate.edu (Marc N Barrett)
Subject: Problems with the A4000
Followup-To: comp.sys.amiga.misc
Organization: Iowa State University, Ames, IA
Date: Sat, 12 Sep 1992 08:38:19 GMT

   For about a week or so, I've been promising to post my detailed explanation
of exactly why Commodore's use of a super-cheap IDE HD interface in the A4000
has very likely pushed the initial list prices higher than what they would have
been had SCSI been used.

   The problem comes down to the architecture of the A4000 itself.  As has been
rumored before, several good systems were canceled not long after DevCon '91,
a year ago.  What has not been said is that these included all of the systems
that Dave Haynie designed that incorporated the AA chipset.  Indeed, none of
the new Amiga systems -- including the A4000 -- were designed by him.  They
were designed in a rush by junior engineers at Commodore.  

   The whole design of the A4000 can be summed up in a fairly short sentence:
the A4000 is an A3000 with the CPU moved to a card, the AA chipset kludged in,
and with the SCSI subsystem replaced with IDE.  I will get back to the issue
of SCSI & IDE in a minute, but I would first like to explain what other 
problems this has.  Basically, the A3000 was not designed for the AA chipset.
The Ramsey and Buster chips in the A3000 were designed for use with the ECS,
in particular the 2M Agnus chip.  The new Alice chip in the AA chipset -- the
replacement for Agnus -- can potentially address 4M of chip RAM.  But since
the Alice chip has been kludged to work with other chips intended for the
2M Agnus chip, none of the new Amigas can use more than 2M of chip RAM.  The
use of the A3000 architecture also has other problems, namely the 
restriction of 16M of fast RAM on the motherboard.  This was not a problem
several years ago with the A3000 was designed, but 16M is not all that 
much anymore, with RAM prices at $34/megabyte for 60nS static-column memories.

   OK, I've established that the A4000 is an A3000 with the AA chipset kludged
in.  Now it makes sense to me that it would have cost less in development costs
to simply leave the A3000's SCSI design there instead of removing it and
replacing it with something else.  The costs of including SCSI in the A4000,
then, would have been practically zero in development costs.  

   In addition to the costs involved in removing the SCSI subsystem from the
A4000's design, though, we also have to consider the costs involved in 
designing the IDE design.  These costs would have been practically zero if
the A4000 had simply used the same IDE design as the A600.  The problem is
that it does not -- the IDE design used in the A4000 is a whole new design.
The new design was created by Randall Jessup, and includes extra hardware to
make the IDE interface and HD look somewhat like a SCSI interface and HD to
Amiga software.  This is a reasonable effort to make the most of a bad
situation, IMO, but the simple fact is that a design like this must have cost
quite a lot to develop, and would not have been necessary had the A3000's
existing SCSI design simply been left in the design for the A4000.

   As Dave Haynie and Randall Jessup have already pointed out, IDE -- even the
new one in the A4000 -- costs next to nothing in terms of manufacturing costs.
But the development costs involved in creating this IDE design must have been
very substantial compared to the costs that would have been involved in
simply carrying over the A3000's existing SCSI design to the A4000.  These
development costs are still costs, and Commodore is going to want to recoup
these costs as quickly as possible.  This means boosting the list prices
to pay the development costs, and then lowering the list prices later as
soon as these development costs have been payed for.  In the short-term, then,
the prices on the A4000 and other new systems will be higher than if they
had used a SCSI design. 

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| Marc Barrett -MB-  |  email: barrett@iastate.edu
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