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==  The Emulation Rambler: ZXAM Spectrum AGA           By:  Bob Colbert  ==
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A Review of ZXAM Spectrum Emulator AGA v1.3
Author: Antonio J. Pomar Rosselló

Initial Thoughts: I am a big emulation fanatic.  I drive my friends crazy
when they come over with the newest AGA demo in hand and I am playing an
old Apple // game on my A1200.  I have seen Spectrum emulators floating
around on the Internet for quite some time now and even downloaded one a
long time ago, but I never had anything to run on it.  I didn't think that
there was much software for the Spectrum, so I never bothered to pursue the
matter further.  I was intrigued to see an AGA emulation of such an old
computer, so I downloaded it.  I decided to do a little homework and found
an FTP site that had a bunch of games for the Spectrum.  The Spectrum
emulator allows the user to play some of the classic games that pioneered
the video game age.  I view the emulation as a means of playing games,
because I really don't think that there are any serious applications that
the emulation can do better than a native Amiga application.

Description: The ZXAM Spectrum Emulator allows the user to run Spectrum
programs on their AGA Amiga computer.  The emulator comes in two forms; The
FULL version that provides very accurate emulation, and the FAST version
that runs a bit faster than the full version at the expense of not
emulating all of the computer's functions.  Along with the executables is
documentation in both English and Spanish, instructions on creating a
cassette tape interface, IFF picture of the aforementioned cassette tape
interface, and an IFF picture of the Spectrum Keyboard Layout.

     Programs are stored in either the snapshot (.sna or .sp) format or on
an external cassette tape recorder.  The snapshots are "images" of the
Spectrum's 48k of ram and are either 49179 (.sna) or 49190 (.sp) bytes long
depending on the format used to save the image.  Loading an image is as
easy as pressing the 'load' gadget on the nice interface provided.  A file
requestor is then presented and you can then load the game of your choice.
One gripe that I have is that every time that I load a file, the entire
directory that I am in is reread.  Since I h ave my Spectrum games stored
on floppies this can take a long time.  An advantage of this emulation
over others that I have tried is that it allows PowerPacked snapshots to be
loaded directly, as long as the user has the powerpacker.library in the
LIBS: drawer.  This feature save A LOT of space.  PowerPacking games can
reduce the original size to as low as 7k!  Of course not all snapshots pack
that well, but when you have a couple hundred images it adds up.  The
emulation also allows you to make your own snapshots at the press of a
key, thus giving all games a 'Save Game' option.  As far as the cassette
recorder format goes, I have been unable to try it because I do not have
any games on tape.  A schematic of the interface needed to use the
cassette recorder is provided, along with a digitized picture of the
finished product.  It is a very simple circuit, and should cost no more
than a few dollars to produce.

     The program provides emulation of what is called the Kempston
Interface, which is just a joystick.  Most games allow you to chose what
type of input you will be using, but for those games that don't allow for
using the Kempston it would be nice to be able to map keys to the
joystick.  I don't like playing games on the keyboard. 
  
     Performance: The ZXAM Emulator seems to run all of the games that I
have tried, and it runs them well.  I was impressed with the speed at
which the emulation runs on my A1200 with 4 megs of fast RAM.  The FAST
version does indeed go faster than the FULL version, but its use does lead
to some interesting problems.  The main deficit of the FAST version is that
it does not emulate the microprocessor's Binary Coded Decimal (BCD) mode.
BCD mode allows the computer to work on the same number base as humans do
- base 10.  Without this, scores, times, and any other items represented
numerically are likely to be inaccurate.  Not all games use BCD and
therefore are not affected, and others you just might not care if the score
is correct (most of the time for me).

     Graphics seem to move around smoothly and the sound is very high
quality compared with other Spectrum emulators I have tried.
Unfortunately, the emulation does not multitask as it takes over the
system.  The emulation can be paused' and the system is returned untouched,
but playing a game while downloading the latest greatest AGA demo is out.
As I said I compared this emulation with a couple others that are
available, namely Spectrum-1.7 and zxspectrum4.71.  Spectrum-1 .7
multitasks, but the sound and movement are not as good as the ZXAM AGA.
Zxspectrum4.71 does not work well with AGA, the AGA graphics must be
disabled before a recognizable screen can be realized.

     Over all, the ZXAM emulator is a solid product, and best of all it is
FREEWARE!  It is available on Aminet under the misc/emu directory.  Also in
that directory is a program you should get called spconv-107-amiga, it
allows you to conv ert between most of the various snapshot formats, most
notably from the .z80 for mat that the ZXAM emulator cannot read into a
snapshot format.  If you have FTP access, you will be interested in
ftp.dcc.uchile.cl under the pub/Sinclair/snaps hots directory are hundreds
of games (and utilities) in alphabetic directories ( i.e.  games beginning
with a are in the a directory.)

Have fun!

                         Bob Colbert
                         bcolbert@s-cwis.unomaha.edu