Subject: Re: Which '040 is this?
To: None <amiga@NetBSD.ORG>
From: None <is@Beverly.Rhein.DE>
List: amiga
Date: 02/07/1996 11:19:49
Patrick Phalen ( wrote:
: >>     The cpu has XC68040HRC25M printed on top along with a smaller block
: >                    ^^^^^   ^^
: >Obviously, it's a 68040/25MHz.  A Full '040.  The EC040's (XC or MC68EC040)
: >had a disabled or nonexistant MMU, and the LC040's (XC of MC68LC040) had
: >a disabled or nonexistant FPU (Floating Point Unit... Aka the Math
: >Coprocessor).
: Okay, now I'M confused. Following is a quote from a review (May 1993) in
: of the Progressive Peripherals Inc. Mercury 68040
: accelerator for the Amiga 3000:

Look at the difference between your chip (without EC) and the chip below
(with EC in it). 
: ------------
:   "The 68040 supplied was not a production chip, but was designated
:   'XC68EC040RC25'.  Contrary to my first angry conclusion, this chip DOES
:   have a full 68040 with MMU and FPU inside, but it has the less advanced

which I don't understand. To my knowledge and that of Motorolas 68040 UM/AD,
there is no such thing as an EC with MMU or FPU or both (Maybe with the exception
of errors at the factory when stamping.) Maybe it didn't pass some test, was stamped 
EC, and he just didn't notice the errors? Then again, the EC is guaranteed to create 
a type 4 (8-word) stack frame on unimplemented instructions, so he would have noticed 
the difference.

:   bus system of the 68EC040.  Also, the "XC" designation means it has at
:   least one minor bug (in the design), and is therefore only for prototyping

To my knowledge, this is wrong. "XC" just means that the particular mask
revision was in distribution for less than, say, a year or so. In any other
respect it is identical to later stamped versions printed off the same
chip mask.

:   purposes.  I have, however, had no problems with it, and it performs in
:   every way like a full MC68040."