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画像:Amiga Format]
This article was originally written by Simon N Goodwin for Amiga Format
magazine, and is used by permission of the joint copyright holders.
It should not be copied any further without written permission.
The free emulators mentioned were included on the accompanying CD with
the magazine, and are generally available - often in updated form - from
this site. The text is as originally submitted to the magazine - which
means there are some differences, mostly extra text which was cut to fit
into the pages available - with the addition of hyperlinks to new or
updated information which has since become available. This approach has
been taken to preserve the structure of the original series, while making
new information readily available. Simon welcomes comments from readers,
care of Tomas Amsrud, who has generously prepared the material for
publication on the Internet.
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AER
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8 bit Apples and Ataris
Simon N Goodwin explores Apple 2
emulators for your Amiga and new
commercial offerings from Blittersoft
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No sooner have we tested PCX, the latest from Emplant impresario Jim Drew,
than two more emulators arrive from his new company, Microcode Solutions.
A][ and ACE emulate eight bit Apple and Atari computers. They're a cut above
most PD and shareware emulators, and reasonably priced at 」19.95 together.
With three free Apple emulators already available, a commercial rival faces
competition. David and Stephen Firth's Atari800, reviewed at Christmas, is
also PD but very slow, demonstrating that Atari emulation is a tough nut to
crack. But if anyone can do it, Microcode Solutions can.
Requirements
The new emulators require at least a 68020 processor, taking advantage of
its speed and ability to read misaligned words. They can run in one
megabyte of RAM, but prefer two megs, preferably 32 bit fast RAM, for good
performance. They use the American keymap rather than the Amiga one, so the
quote, hash and at symbols are not where Europeans would expect them. Other
keys appear in their usual Amiga positions.
ACE and A][ need Amiga Kickstart 2.04 or better, and do not include the
original system ROMs. The Atari emulator has ROM emulation, but to run Apple
2 software you'll need the system and BASIC ROMs from a real Apple, or as a
file from CD or the Internet. Sound, colour and mono displays are emulated.
Eight bit Ataris and Apples were produced for a decade from the late
seventies and periodically tweaked to boost performance and sales.
Microcode Solutions set out to emulate the Atari XL and XE, Apple 2C
portable and the 2GS super-Apple,as well as the original machines.
The Atari Console Emulator - ACE for short - is written by Joe and Mike
Fenton. Don't confuse it with the big, slow 'Atari Computer Emulator'
written in C for Unix boxes.
On the Amiga, ACE challenges the freeware Atari800, another Unix
conversion. ACE makes full use of Amiga sprite and sound hardware, and it
shows. Processor emulation is written in machine code rather than C, giving
a colossal speed advantage.
In BASIC ACE can loop 10,000 times in 14 seconds at standard settings,
compared with 48 seconds for the same test with Atari800 - about thirty per
cent of the speed of the real thing, on the fastest Amiga currently
available! Keyboard response is instant with ACE, while it lags on Atari800
- although the new release 0.6 is some improvement.
Selecting 'unlimited' speed on a Cyberstorm 68060, ACE runs the same test
in under four seconds - three and a half times faster than a real Atari,
equivalent to a 6502 at over 6 MHz, and ten times the speed of its freeware
rival. ACE delivers full Atari performance on any 68040 Amiga, and performs
respectably on a 68030.
Some of the speed of ACE in BASIC comes from passing arithmetic
calculations through to the Amiga. Pressing right Amiga and M toggles this,
but the difference is not just speed: PRINT 1/9 gives 0.11111111
(correctly) by default, but 0.121951219 thereafter! This suggests a BCD
emulation bug, but all is well if you leave the default setting.
Sound and Graphics
ACE is multi-tasking, although like A][ it uses a custom screen so you
can't grab images as you could with a standard Amiga window. You can run
two at once, and prioritise emulators when displayed and hidden for best
multi-tasking performance. The defaults are well chosen.
Like Atari800, ACE supports ECS, but makes best use of the extra colours
and improved sprites of AGA. Some Atari programs re-use sprites but ACE does not emulate this
correctly, so a horde of horsemen in Necromancer appears as a vertical
column, rather than a scattered group. Atari800 gets this right, but at
great cost in speed as it renders each sprite into the background.
Qix looks and sounds fine but collisions between the Qix and the player
were ignored, ruining the game. Centipede, Adventureland, not-so-super
Mario's 1981 Nintendo debut Donkey Kong and the immortal Star Raiders all
run perfectly.
Sound emulation is extremely impressive - the best of any eight bit emulator
on the Amiga, and practically indistinguishable from the real thing, except
that it's in stereo! To manage this, ACE uses all four Amiga sound channels.
Key features
The Amiga function keys emulate START, RESET and so forth on the Atari,
with Right Amiga and other keys used to control emulator features. A start
-up menu appears on a custom screen when the emulator is launched, and a
help screen shows the layout and assignment of Amiga keys.
Configuration is essential. Some Atari disk programs need the 8K of memory
occupied by the cartridge slot, while others need BASIC. A few are fussy
about the ROM version - ACE supports the original Atari 800 and 400 ROMs,
although it has ROM emulation good enough for most games, but not BASIC.
ACE menus feature the XL and XE models as well as the original Atari 400
and 800; the main difference is the amount of memory free for programs. It
supports European PAL and American NTSC display formats, which have
slightly different timing on an Ataris, as on Amigas.
You can preset these options with Icon tooltypes, or adjust them on a
workbench control panel, much like those used with Shapeshifter and PCX.
Other controls configure serial, printer, cassette and disk file re
-direction to use Amiga hardware or Atari peripherals, via an adapter.
ACE
DISTRIBUTOR: Blittersoft 01908 261466
PRICE: 」19.95
Speed
Impressively fast
Documentation
No monitor details
Compatibility
Needs some work
Value
A lot of work for the price
OVERALL VERDICT:
A very promising debut.
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83% |
Filing
ACE supports up to ten simulated disk drives and re-directs Atari tape
CSAVE and CLOAD commands to an Amiga file requester. ACE recognised all the
disk, file and cartridge formats I threw at it, but some later releases are
incompatible with the Atari 400 ROM it uses or emulates.
If you're confident of your hardware skills you can link the emulator to a
real Atari system with a cable from the Amiga parallel port to a couple of
the all-purpose Atari controller ports. The documentation includes a circuit
diagram and programs in 6502 and 68000 code to manage each end of the net,
but you must type the 6502 code into your Atari to get started.
The Atari has four controller ports, but the Amiga has only two. Switched
joysticks and CD32 controllers are supported, but unfortunately not
analogue joysticks or paddles, although the Amiga mouse can emulate the
first two Atari proportional controllers.
Documentation is an decent Amigaguide with a keyboard graphic. I'd prefer
printed documentation, with more discussion of compatibility and optional
combinations, but got it working with a little trial and error - more
related to my dim memories of the original machine than emulator problems.
Amiga B calls up an impressive-looking but sadly undocumented built-in 6502
code debugger.
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The Apple 2 was a very early home computer, introduced at the end of 1977.
The previous Apple model was a bare board which sold only a handful of
units, but the Apple 2 was a much more professional - and expensive -
offering, with a neat case, keyboard, internal power supply and expansion
slots. The only obvious omission was a TV output, skipped to avoid the need
for Federal Communications Authority approval, but readily available from
other firms, at least in the USA.
For its day, the Apple had quite remarkable features, including sixteen
colours (at a VERY chunky 40 by 48 resolution), high resolution colour
graphics (its 280 pixels per line were unprecedented in a 1970s micro,
though small beer today) and support for up to 48K RAM.
Apple 'hires' gives six colours from under 8K; a zero byte gives seven
black pixels. Adjacent set bits come out white, but odd and even bits in
groups of seven appear orange and blue, or purple and green, depending on
the setting of the eighth bit! It's MPEG writ tiny; designer Steve Wozniak
brilliantly exploited TV display limitations.
Disk drives soon arrived, although the Apple never used a conventional disk
controller, relying on Woz's software and an eccentric but effective
interface made from cheap 'glue' chips. It is possible to read Apple disks
on an Amiga, using the obscure GCR decoding scheme, but it's easier to grab
files from the net or CD. The PD utility Disk2File reads Apple DOS 3.3
disks from an Amiga 1020 drive.
Apple disk image files are about 140K in size, accessed at authentically
slow pace. Apple2000 comes with AFID, a utility to manipulate files inside
a disk image, and reassuringly shows the 'track' number being accessed as
it goes along.
A][ is Mike Fenton's Apple 2 emulator, bundled with ACE. It can emulate a
48K Apple 2 with a language card and two disk drives, but needs Apple's 12K
ROM image. Cassette files go directly to Amiga drives; there's no handler
for genuine Apple media. One bit sound is supported.
Apple game paddles are emulated with the mouse or numeric pad. Neat icons appear
momentarily when you change these, or the speed of emulation, with function
keys. The Amigaguide is skimpy - the monitor is not documented at all - but
compatibility is good, and almost everything I tried worked first time.
Free Apples
The greatest challenge to A][ comes from Kevin Krillian's Apple2000, a very
competent emulator which has been in free circulation since 1994. At one
point Utilities Unlimited demonstrated it as the promised 'Apple 2 module'
for Emplant, but that deal fell through.
Apple2000 is on the C64 Sensations Volume 2 CD, with the required ROM
image. It's also on Aminet but in that case you must get the ROM
separately. Like A][, Apple2000 demands at least a 68020, Workbench 2 and 900K free RAM. I had to
disable the 68060 data cache momentarily during start-up to prevent
sporadic gurus. Speed can be unlimited or configured from half to double
normal, in 50% steps.
The author recommends a 25 MHz 68020 for full speed, and a two-button
joystick for compatibility with real Apple sticks. Real Apple joysticks use
proportional controllers, rather than Amiga-style switches. If you've
already got a proportional controller Apple2000 can take full advantage of
it, and this can make all the difference to emulation of some programs.
My stopwatch revealed that Apple2000 was almost four times faster than A][
on simple BASIC, although A][ almost caught up on a hires graphics test. At
best Apple2000 ran eight times faster than a real Apple on my Cyberstorm,
with good softwarecompatibility.
The old A2
Richard Skrenta's A2 was one of the earliest Apple emulators for the Amiga.
It's supplied in source form, with a sample disk image which also works
with other Apple emulators.
A2 is entirely written in C, which makes it slow. It incorporates a monitor
with useful memory, file and 6502 debugging options, and supports official
6502 and 65C02 instructions, Apple DOS 3.3 and the later ProDOS.
A2 can emulate a 16K language card as well as the main 48K RAM of an original
Apple 2, with integer or 'Applesoft' ROMs, but these are not included.
There's software to transfer ROMs and disk images. A2 is slow and a bit
hard to use, even though key ROM routines are re-written for speed.
AppleOnAmiga is another early effort, this time with source in Modula 2.
Like A2, it's incomplete and documentation is scarce - unless you're fluent
in Modula - but A2 is free and has some features which might repay the
interest of programmers.
Verdicts
A][ works fine but Apple 2000 is better in some respects, and free - see A][
as a 'free gift' with ACE and you won't be disappointed. The menus describe
ACE as version 0.1 and it's still early days. It ran half the programs I
tried, giving a scrambled screen or messages on the rest. When it works, it's
awesome - technically one of the most impressive eight bit emulators on the
Amiga, capable of running excellent software even by 1990s standards.
Further development should improve compatibility; I'd like to be able to use analogue
joysticks and paddles. For emulator enthusiasts and former Atari eight-bit owners,
ACE is already worth getting, and has the makings of a classic emulator in every sense.
A][
DISTRIBUTOR: Blittersoft 01908 261466
PRICE: Free with ACE
Speed
Quick 040 required
Documentation
Rather skimpy
Compatibility
Generally good
Value
How can you compete with 」0?
OVERALL VERDICT:
Apple2000 blows it away.
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71% |
Web page design Copyright © Tomas Amsrud
Articles Copyright © 1996-2002 Simon Goodwin
