/// The Emulation Examiner
    ----------------------
    By Jason Compton
    (jcompton@mlinknet.uucp)



Among the many talents of the Amiga lies in the ability to emulate pretty
much any computer on the market, provided someone wants to sit down and
develop a hardware or software or both method way of doing it.  To say I 
have an avid interest in this is sort of exaggerating.  I'm obsessed with 
it, and have done my best to find out as much as I can about just how well 
all of it works.  Believe it or not, some of it is actually useful, 
practical, and cost-effective.  I'll examine the lowest-cost options for 
emulation I know of:  Questronix's A64 Package and three software-only 
IBM emulators.

The A64 Package is a good place to start.  It is a Shareware product, with 
the approximately $40 registration fee getting you a better version and a 
hardware interface which plugs into the parallel port and gives you full 
support to 64 daisy-chainable peripherals on A500s and 2000s (the 3000, and 
presumably the 4000, has a bus that's just too fast for the 64.)  The 
software comes as two disks, one with the program, the other with the 
detailed documentation and utility programs, which allow for 64-Amiga 
copying, 64 DOS options, and optimization and 680x0 conversion of "frozen" 
A64 programs. It also provides for usage of real 64 ROMs (the package comes 
with special kernal and BASIC rom files written by Questronix), access to 
the PRT: device (assuming you have a parallel-port multiplexer or forego 
the hardware interface for a time), partial serial emulation (I've only 
been able to connect at 1200 baud), and joystick port access.  The package 
is great if you want to stroll down memory lane, switch some files between 
the 64 and Amiga, maybe use an old 64 program you haven't been able to use 
in a while, but it doesn't replace the real thing.  First off, it's rather 
slow on a stock Amiga, and while it supports the 68010-030, there is no 
word in the documentation about the 68040.  In all fairness, it runs near 
100% on my 68020/14, but that's not all of it.  A64 doesn't support most 
fast loaders, so most of your games are out.  The games that don't fall 
under this category probably won't work very well, because while A64 
supports sprites, it has a very difficult time with raster interrupts. 
This causes a lot of problems, and pretty much no graphic demos will work 
properly.  There is sound emulation present, but you're pretty much better 
off without (ever heard a PC speaker? This is a notch above.) For free (or
for $40 for the emulator), who's complaining? It doesn't promise anything 
it can't deliver, and is perfectly well suited for any 64 program which 
doesn't want to use a raster interrupt. 

Now, on to the IBM software-based emulators, one commercial, one shareware, 
and one with a status I'm really not sure of.  I'll begin with that one to 
get it out of the way:  Amiga Transformer, a 286-emulating program which is 
really only worth mention as a curiosity, and because it emulates a 286.  
It takes over the system completely and irreversibly (well, you can reset, 
but you know what I mean), is 2.0 unfriendly, monochrome only, and provides 
no port emulation that I'm aware of.  Its one redeeming quality might be 
that you can use 4 floppy drives with built-in MS-DOS emulation, but that's 
a questionable plus.  Since the release date on it states 1988 and I've 
never heard of it being offered for sale or as Shareware, I'm completely in
the dark as to its status. But that's probably a good thing, as it's mainly 
just going to come in handy if you're DYING to see an A:> prompt.

Next, onto the commercial product:  CrossPC, available with Consultron's 
newer CrossDOS programs. Formerly the Shareware emulator IBeM, this program 
emulates an 8088 with CGA.  As IBeM, it was a real pain getting drives to 
work with this, as you needed to reassign them in mountlists with a CrossDOS 
or similar filesystem, etc. etc... now that it's included with CrossDOS, I 
believe things have gotten a bit simpler.  To my knowledge, the CGA
emulation is faithful enough (how tough can it be, it's CGA).  I am unsure 
as to how it handles ports.  I do know that the original IBeM had an 
enhanced version for processors above the 68000, which is basically a must 
(I'll explain at the end of the article).  If you're going to buy CrossDOS,
you may as well give CrossPC a look, but CrossPC isn't worth the full price
alone...but will run XT programs that don't make intense BIOS calls (again,
I'll explain later) with respectable faithfulness.

Finally, the flagship of the software IBM emulators: the Shareware-prolific 
Chris Hames' PC-Task.  With the advent of V2.0 of his 8088 emulator, Hames 
added EGA and VGA emulation to his program (which on AGA machines can be 
used as a full 256 color VGA screen).  While I've found that GIF viewers 
don't want to touch the EGA emulation (not enough video RAM allocated by 
PC-Task for EGA), the VGA is real enough, in the video modes my 2000 gets 
me for the program.  PC-Task supports two floppy drives with its own MS-DOS
reading system, as well as supporting up to two Bridgeboard PC hard drive 
files, which to my knowledge is unique among software emulators.  PC-Task 
enables you to choose the task priority for the program when it is both 
elected and unselected.  It provides serial and parallel ports for the 
emulation, and is overall the best software-based PC emulator available.

Hames' shareware pitch is to disable all disk writing until you pay him 
$40, which is really sort of reasonable considering surplus supplies of XT 
Bridgeboards are going for about $50, with only a 360k 5.25 drive available 
to the Bridgeboard.

Now it's time to point out some drawbacks that all of these PC emulators 
share.  First, and most obviously, they are limited by speed.  It's not the 
easiest thing in the world making a Motorola chip want to be an 8088, so a 
lot of effort goes into doing it.  For instance, I've found that on a 68000 
machine, a PC emulator gets somewhere near .5 mhz.  That's really, really, 
really slow.  A 68030/25 should have no problem getting the 4.77 mhz of an 
8088, and then some, though, based on the improvement I get on my '020/14.  
BIOS support is another issue to consider: any program that wants to take a 
look at the PC's BIOS is going to be in for a big surprise, because these 
emulators seem to have enough to get by, and that's about all.  I have only 
been able to get one system information program to work on these emulators, 
and it was a very old one which I can no longer find (but it got me the 
speed reading).  Memory is another consideration: on a 1 meg Amiga, you can 
get somewhere near 500k of memory on an emulator, which isn't a whole lot. 
Unfortunately, as much memory as you may have, you'll only get up to 704k 
before the emulator can't support any more... of course, for an XT program, 
that shouldn't be a problem.  But there will be no XMS available, ever.  
Then, of course, should you ever get really involved with a nice emulation 
system, say a 4000 running PC-Task in VGA, you won't get niceties like a 
joystick or sound card...(PC-Task and I believe CrossPC do provide mouse 
emulation, however).  In all, if you're not planning to be a power-PC user 
(no pun intended), going with a software-based emulator might just be 
enough for you.  In the future, I'll cover what I know of IBM hardware 
emulation (doing my best not to repeat the work of Dave Johnson's 
AmigaWorld article on hardware emulation...), Mac emulation, and anything 
else that happens to come up with any remote focus on whatever I have been 
or will talk about.  Please send me mail with your questions, comments, 
experiences, etc. with emulators.  Amiga Report willing, we'll meet again 
soon...