From: doiron@starpt.UUCP (Glenn Doiron)
Newsgroups: comp.sys.amiga.misc
Subject: Re: Problems with the A4000
Date: 14 Sep 92 21:51:03 GMT
Organization: 68K Software Development
X-NewsSoftware: GRn 1.16e (7/4/92) by Mike Schwartz & Michael B. Smith

In article <1992Sep12.083819.17967@news.iastate.edu> barrett@iastate.edu (Marc N Barrett) writes:
>    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.

Tune in next week for Marc's explanation of why Surface Mount Technology
pushes price higher than conventional assembly methods.

>    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.  

Whose names Marc will withhold because He Doesn't Know.

>    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.

Here it is folks- the great Marc Barrett facts.

> 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.

Well, one fact in an entire article is pretty good for -MB-.

> The Ramsey and Buster chips in the A3000 were designed for use with the ECS,
> in particular the 2M Agnus chip.

Ramsey and Buster have nothing to do with ECS.  Ramsey controls the fast
ram arrays/SCSI address generation.  Buster controls the Zorro3 bus.
Neither Ramsey nor FAT Buster (which is the correct name for the chip in
the A3000) have anything to do with ECS, indeed they are only connected to
the local CPU bus (and Ramsey is, of course, connected to the motherboard
fast RAM).  Chip RAM arbitration is somewhat complicated, but I'll
simplify:

1.  Chip RAM is made up of 2 16-bit (512k or 1meg, depending on how much
chip RAM you have) banks.  Special "Bridge" circuitry electrically connects
the two data busses together.  When Agnus wants to access the "near" 16-bit
bus the bridge circuits do nothing.  When Agnus accesses the "far" 16-bit
bus the bridge circuits kick in, moving the "far" 16-bit data onto the
"near" bus for Agnus to get at.  When the CPU accesses chip RAM, *BOTH*
busses are accessed SIMULTANEOUSLY (bridge & cpu logic are provided via the
morass of PAL's on the A3000's motherboard).  So, now you can see, Ramsey
and Buster have *not a thing in the world* in common the the ECS chips,
except that they might be in the same machine.

> The new Alice chip in the AA chipset -- the
> replacement for Agnus -- can potentially address 4M of chip RAM.

Sources please?  Do you have Barrett (TM) X-RAY VISION that lets you see
schematic diagrams thousands of miles away in Westchester, PA?  Or perhaps
you glanced a peek at the top layer of a multi-layer motherboard and
deduced all the traces?

> But since
> the Alice chip has been kludged to work with other chips intended for the
> 2M Agnus chip,

Err.. yeah, whatever.  You should check your "inside" sources at Commodore
again.

> none of the new Amigas can use more than 2M of chip RAM.

This may or may not be the case of the Alice chip.  Since I don't have any
technical specs either, I'm not going to overtrump your BS with my BS.
Suffice it to say that I as a developer have received *NOTHING* that states
that Alice can address 4 megs of RAM.

> The
> use of the A3000 architecture also has other problems, namely the 
> restriction of 16M of fast RAM on the motherboard.

Yes, but how that suddenly became a restriction or why you can't use the
ProRAM-3000 boards in the A4000, only you know...

> 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.

Duh, like it would be cheaper to redesign Ramsey to address more RAM.  Few
people even have the whole 16megs that they can in their machine.

>    OK, I've established that the A4000 is an A3000 with the AA chipset kludged
> in.

No, you've established that you have absolutely not a (ahem) CLUE about
what you're talking about.  But, I digress.  You've already proven that
many times.

> 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.

Pretty ridiculous.  So your whole bullshit argument revolves around the
bullshit which you've tried to prove with bullshit.  Eeew, what did I just
step in?

> The costs of including SCSI in the A4000,
> then, would have been practically zero in development costs.  

Just about as much as including IDE, maybe more, considering what IDE
really is.  All the s/w work was done by Randell Jesup for the A600 anyways.

>    In addition to the costs involved in removing the SCSI subsystem from the
> A4000's design,

...this should read: "...involved in not putting SCSI in there in the first
place"

> 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.

Hardware-wise it's trivial.  Software wise it's trivial too- all the work
was already done on the A600.

> The problem is
> that it does not -- the IDE design used in the A4000 is a whole new design.

Wooooooooweeeeee.  Big farts.  Even if it is a "new design", it still costs
less to put IDE on than SCSI, although I don't agree with the decision on a
design level myself.

> 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.

All that "new design" is in fact "old design" because it was already done
on the A600 which was also announced at the show.

> This is a reasonable effort to make the most of a bad
> situation, IMO,

No, my reply is a reasonable (IMHO) effort to make the most of a bad
situation (more -MB- facts).

> but the simple fact is that a design like this must have cost
> quite a lot to develop,

New machines do have a tendency to be that way.

> and would not have been necessary had the A3000's
> existing SCSI design simply been left in the design for the A4000.

Since your point is moot (as pointed up above), this statement simply does
not apply.
 
>    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.

Therefore it will cost less to produce each unit.

> 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.

Development on SCSI was already done.  Development on IDE was already done.
Since carrying over SCSI would mean carrying over extra chips like the
WD33C93A/SuperDMAC/glue logic, it would be more expensive than the itty
bitty piece of space on a chip they use for IDE logic.

> These
> development costs are still costs, and Commodore is going to want to recoup
> these costs as quickly as possible.

Yep.  Expensive first, cheaper later.

> 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.

Duh.. was Economics one of those courses you weren't sleeping through?

> 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. 

Yeah, sure.  Whatever.

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

Glenn Doiron
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