AMIGA RAM

   What kinds of RAM Amiga has?  Well,
that's  easy:  Chip and Fast.  Chip is
the portion in which...    NOT TRUE!!!

   Once  again  Commodore proved to be
unreliable,  confusingly unlogical and
utterly  stupid!   When  people bought
A501  memory  expansion  for Amiga 500
they  thought  that  they got 0.5MB of
Fast  RAM.   Well,  they didn't!  They
were  cheated by Commodore!  What they
got was 0.5MB of Chip RAM disguised to
be  recognised  as  Fast!   The system
thought  (as well as the user) that it
is  the Fast memory, accesible only by
the  MC68000  and therefore faster, as
it  didn't  have  to  share bus cycles
with custom chips.  But, in reality it
didn't   have   none   of   the  speed
advantage  of the Fast memory, it only
had  the disadvantages!  The REAL Fast
RAM  on  Amiga is mapped from $200000!
That's  the  only  RAM  in which 68000
really  operates  faster.   (This fact
may  be  invalid on Amigas with 2MB of
Chip, but as I didn't encounter any so
far, I'm not sure where their Fast is
mapped.)
   If  your  Amiga  500  has  rev6  or
higher   motherboard   revision,  that
'Fast'  memory,  mapped  at $C00000 is
mirrored from $80000 to $100000, so if
you're  a coder you can take advantage
of  that:   if you're not using system
procedures  you  can  use  that memory
exactly  the  same as you if had 1M of
Chip    RAM.    That   means   blitter
operations,  screens,  music, anything
can  be  placed  and  executed in that
part  of the memory.  You just have to
adress  to  it  from  $80000, not from
$c00000!   Furthermore,  you  can make
that  memory appear as a real Chip RAM
just  by resoldering one jumper on the
motherboard.   I  can't remember which
one  at  the  moment,  but  if want to
know, contact me and I'll look it up.
   Why did Commodore do this?  It is a
mystery.   The internal expansion slot
of  the Amiga was allways planned only
for Chip RAM or other peripherials, it
physically can't be used for Fast RAM,
so why did they introduce A501 as Fast
RAM  expansion,  although knowing that
it  isn't?   Part of the reason may be
that  at  the  time there still wasn't
Agnus chips capable af handling 1MB of
Chip,  but  then  why did they make it
map at $c00000 even on Amigas with Fat
Agnus?   The answer to this one may be
that  these  Amigas have capability of
installing 1MB of Chip directly on the
motherboard,  but then why didn't they
document  that option, and why is that
jumper factory soldered to 'fake Fast'
position  although the space for extra
0.5MB of Chip on motherboard is empty?
The A500 could have been equipped with
1MB  of  Chip RAM as standard as early
as  1989!   Why wasn't it?  The stream
of  questions  could  go  on for quite
some  time,  still  without  any  good
answers.
   It   seems  that  Commodore  really
doesn't   give   a  damn  about  their
customers  and  even about the quality
and  competitivness of their products.
With   this   kind   of  attitude  I'm
wondering how the hell they think they
will  survive  in  the  future?   With
merely  minor  efforts they could have
made the Amiga much more as popular as
it  is  today,  and at least two times
powerful   on  the  market,  but  they
rather  go on with bad policy and even
worse products...


           DR.J/PLS