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Tools - YAPE
Last updated:2018-03-18
Created by:G., Attila (Gaia)

YAPE is short for Yet Another Plus/4 Emulator. Has been in development since 2000 and is still actively developed. Visit the homepage for the latest version and the description of its features.

Keywords: Commodore 16 Emulator, Commodore Plus/4 Emulator

Yape User Manual

YAPE (Yet Another Plus/4 Emulator) is copyright Attila Grósz, 2000-2017


What is YAPE?

YAPE is a Commodore 264 family emulator. It's an 8-bit microcomputer
family from the once-great-now-defunc Commodore Business Machines Ltd.
They were released as a successor to the immensely popular Commodore 64
supposedly to either compete with the ZX Spectrum or other micros but
eventually failed to gain market success and the whole line was dumped
within a couple of years. However they were hugely popular in a few
countries such as Hungary, Germany or Italy (to a certain extent also
in the UK).

The program features an accurate cycle-exact approach and a high
level of emulation. The user interface aims to exploit the potentials
of the Windows operating environment. The emulator is written in C++
and is compiled with MS Visual C++. There's an older port to other
platforms than Windows (using the SDL
). In the future there'll probably be other ports made.

YAPE was born out of a disassembler project during the summer of
2000 and had been for some time the only actively updated Commodore 264
family emulator. See the Changes.txt for development and release

Minimum system requirements

Since YAPE is a cycle-based emulator (much like the Commodore 64
emulators Hoxs or Frodo), its system requirements are higher than that
of other line-, instruction- or event-based emulators. In return however, it makes
development easier for me while providing maximum possible accuracy. For
attaining 100% relative speed to the original hardware, you need:

PII 333 MHz or higher without sound and true drive emulation.

PII 500 MHz or higher for both sound and true drive emulation.

8 MB VGA card capable of DirectX 3.0

Sound card (DirectSound compatible)

Windows 9x, 2000/XP (and NT 4.0 without sound)


All the known 264 family members are emulated:

  • Commodore 16/116 (optionally with 64 KB memory extension)

  • Commodore 232 (prototype unit with 32 KB RAM, never sold)

  • Commodore plus/4

  • Commodore V364 (prototype unit, 64KB + Speech hardware)

You can select the desired machine configuration from the 'Machine'
submenu's Configuration option. The Commodore 364 prototype unit is also
emulated even though the interfacing (MOS 8706R0 custom ASIC) between the
machine and the speech hardware (Toshiba 6721A speech synthesizer LSI) is to
some extent unknown. Note that it is real emulation, not 'simulation', no
speech samples are used, but all the utterances are generated realtime, on
the fly.

The following hardware components are emulated:

  • cycle exact CPU (MOS 7501/8501) and TED (MOS 7360/8360) emulation

  • cycle exact 1541 drive emulation (6502 CPU, VIA 6522 i/o chip and FDC

  • cycle exact 1551 drive emulation (6510T CPU, TIA 6523 i/o chip and FDC

  • 100% of regular and illegal CPU opcodes are implemented

  • 16K, 32K, 64 and 256 KB RAM configurations are all supported

  • all TED character and graphic modes

  • rasterline exact hardware cursor

  • timer and raster interrupts

  • PAL and NTSC video modes with most known artifacts

  • full ROM banking and external cartridge support (in raw format only)

  • PRG/P00/D64/G64/T64 image format support, also ZIP-ped

  • TAP image support, both MTAP and digital samples (aka WAVs)

  • keyboard+joystick emulation via the PC keys and/or joystick

  • full TED sound (generated noise and 2 channel square wave), decent
    SID-card emulation (both 6581 and 8580 selectable) with custom chip

  • simple high- and low-pass sound output filter; oversampling filter for
    TED sound

  • functional T6721A Toshiba speech chip and custom MOS 8706R0 glue chip

  • user port (RS-232) lightpen

  • partial PAL emulation (dynamic YUV palette: brightness, contrast,
    gamma correction, saturation; the emulator expects 'valid' vblank
    signals otherwise the emulator screen may start flickering like the real

  • emulator and multimedia snapshot (video, audio), screenshot support

Note, that the SID card and the 256 KB RAM are hobbyist extensions to the
original hardware and not to be found in stock machines.

The following are not emulated at
the moment:

  • all low level TV signals

  • 157x series of floppy drives

There are three emulation accuracy levels. These are:

  • low level: the emulation is
    line based, the timers are also updated every line only. Provides very
    good performace on older computers while at the same time adequate
    accuracy for playing most of the well-known classic games, though true
    drive emulation is not available. Also do not try running demos in this

  • high level (default): the
    emulation is very accurate, the only missing features are the video
    shift register emulation and a few weird quirks of the clocking. Runs
    99.9 percent of the programs perfectly, only a handful of demos will
    fail, that are deliberately overwriting the horizontal counter (and not
    even all of them fail per se)

  • very high accuracy: all
    known TED effects are emulated, should run all programs ~100%
    accurately; if not, report it immediately :)

In case you're coding a demo, the last option is the best choice, otherwise
just go for the default option. If your computer is made prior to 1999, then
you probably have to use the low level mode.

YAPE can interact with the Windows operating environment in the following

  • You can copy the contents of the
    screen memory to the Windows clipboard
    by pressing ALT+C

  • You can copy the contents of the
    Windows clipboard to the emulator
    . In this case the clipboard
    is interpreted as text and will be feeded to the emulated machines's
    keyboard buffer

  • You can associate YAPE with the
    most common CBM emulator images
    (PRG, D64, G64, TAP). Select
    'File associations'from the File menu and tick the file extensions you
    want to get associated. Untick causes the association to be deleted from
    the Windows Registry.

  • Drag'n' drop support: by
    dragging a supported emulator image over the window of the emulator,
    it'll get autostarted as if you had selected 'Autostart image' from the
    menu. If you drag an image file with the Ctrl key pressed it won't
    autostart though.

  • Always on top: you can force
    YAPE to be the topmost window on your desktop even when it's not the
    active window. Select 'Always on top' from the Screen menu

  • You can make screenshots ofthe
    screen in BMP or GIF format by pressing F6. The file gets placed in the
    current folder (not necessarily where the emulator resides, but where
    you the last time have programs loaded from). If you have loaded a PRG
    or P00 file previously, the name of the screenshot will be
    PROGRAMNAME0000.BMP otherwise it'll get a name of YAPE0000.BMP where
    0000 is a serial number so you can place more screenshots of the same
    program (up to 10,000) in the actual folder without overwriting the
    older ones.

  • You can make multimedia snapshots,
    either in video or audio format. When recording to video, first you will
    be presented with the default codec-selector dialog window where all the
    system-wide installed video encoders are present. Choose one that
    supports both audio and compressed video otherwise the resulting video
    file may become enormous (or wihout sound). Sound snapshots are
    presently only available into 16 bit mono, 44,1 kHz uncompressed PCM
    (WAV) format.

  • You can switch to full screen mode
    and back to windowed by pressing ALT+ENTER or selecting 'Full screen'
    from the Machine menu. Full screen mode is meant to be the quickest as
    it uses DirectX and direct primary surface access. Select it of you
    experience speed problems on your PC. The best performance  in
    windowed mode can be achieved with the 'Use GDI' option from the Screen
    menu and by turning 'Double screen'off. Also this is the most compatible
    screen mode. Unfortunatley, the user interface is limited in full screen
    mode, so you may have to switch back and forth if you need a certain UI

Installing and running the emulator

Installation is simple: just copy all the files from the ZIP file into a
separate folder on your hard disk. You start the emulator by simply double
clicking on YAPE.EXE. If you have associated some emulator image formats
with YAPE, you can also start it up by doubleclicking on the image. To
set/amend the associations, simply select 'File associtioans' from the
'File' menu. Alternatively, you can also use Yape with the always on top
option and drag'n'drop.

Once running the emulator, you can PAUSE it any time by pressing the
Pause/Break key or selecting this option from the Machine menu. Once
paused the emulator will not use up your PC's CPU resources. Pressing the
Page Down button will advance the emulation by one single frame.

The following command line options are supported at the moment:

  • '/DISK#:image' for attaching an image to drive {8,9,10,11} at startup

  • '/LOAD:textfile' for typing text from 'textfile' on startup

  • '/TAPE:image' for attaching a TAP/WAV image on startup

  • '/TYPE:text' for typing 'text' on startup

  • '/NOSTART' will suppress autostart

  • '/BREAK:address' will set a breakpoint to the given address that can
    be both decimal and hexadecimal (0x0000 format)

While using the emulator, you can monitor some internals by pressing
SHIFT+F9 or selecting the 'Quickdebugger' option from the Screen menu. The
following information is displayed then:

  • internal registers of the machine CPU (on the left side)

  • a simple tape counter (simply the offset in the TAP or WAV file)

  • when a disk drive is emulated on the CPU level, you can also see:

    • the PC of the drive CPU

    • the drive LED (black when no activity, green when the drive motor is
      on and red during error or other activity)

    • the current track and sector number

You can toggle on/off the speedometer by pressing ALT+S or selecting the
'Display speed' option from the Screen menu. The default speed is 100% which
means that the emulator is running 100% of the original machine's speed, and
50 FPS (frames per second) which is the PAL standard, or 60 FPS (NTSC). You
can select a lower or higher speed the top speed is limited only by your
hardware (the processor and the graphics card both have an effect as well as
your emulator settings). If you have a slow graphic card, you can select a
lower framerate from the Screen menu but that may cause the screen to
flicker. The fastest display mode is full-screen, but the graphical user
interface is then mostly becomes unavailable from there. You can still use
most keyboard shortcuts though.

If for some reason during tape loading for example) you want to boost the
speed to the very limit you can select the 'Full throttle' option from the
Machine menu (or alternatively press ALT+W). This will turn off sound, set
the frame rate to a certain number of frames per second giving the emulated
machine more CPU power.

Just like the real machine, you can reset the emulator, too. The switches
are accessible from the 'Machine' submenu. The following reset variances
are supported:

  • RUN/STOP + reset (TAB+F11): equivalent to the one on the real machine;
    jumps to the machine language monitor without losing memory conents and
    BASIC programs and variables.

  • Soft reset (F11): equivalent to pushing the white RESET button of a
    264 computer. You will not lose the memory contents only BASIC programs
    and variables. If a program masks the RST vector,you may not be able to
    restart the emulated machine this way.

  • Hard reset (SHIFT+F11): equivalent to turning the power on and off in
    a real machine in that it clears all the RAM contents

  • Forced reset (CTRL+F11): will always jump to the ROM reset vector,
    even when it's disabled. Great for debugging.

  • Drive reset: eventually drives may crash, too, so they can be reset
    here, all at once or individually. This is the equivalent of turning the
    drive off and then on.

You can quit the emulator in several ways: ESC key quits with a
confirmation dialog window, F12 and ALT+F4 quits immediately.

Loading and starting programs

Most Commodore plus/4 programs are distributed in either PRG (raw) or D64
(disk format). There are some other formats as it was noted above but they
are much scarcer. The most convenient way of loading programs to YAPE is
to choose 'Autostart image' from the File menu (or by pressing F7). You'll
be presented a file dialog window where all supported images in the actual
folder can be seen. If you select any of them, YAPE loads and tries to RUN
it. If the program is in PRG/P00 format and has a SYS startup code, it'll
fail. In that case you have to find out the start address yourself
(probably from the file name or the documentation). Note, that the
autostart feature will reset the emulated machine hence all previous RAM
contents will be lost.

There are other ways of loading programs to the emulator, but these are
dependent on the format, and won't be started automatically. Also the
memory contents will not be lost:

  • for PRG and P00 files you can press F8 or select 'Load PRG' from the
    File menu

  • for TAP images you can select the 'Attach TAP' option from the Tape
    menu then type LOAD and press ENTER. You are faced with a text that says
    'PRESS PLAY ON TAPE'. To press the Play button the virtual tape device,
    press F5 or select 'Play' from the 'Tape" menu

  • for D64 images you can press ALT+D or select 'Attach D64' option from
    the File menu: in the file dialog you can see some other options. If
    you're emulating a 1551 drive in YAPE, you can select under which drive
    number you wish to attach it. You can also create an empty D64 by
    ticking the 'Creaty empty D64' option.

  • T64 and (P)SID images you can currently only attach within the
    'Autostart image' option

For games, demos and programs, visit: or
or or

On how to make TAP or WAV images from your original tapes that can then be
loaded into the emulator, visit:

Keyboard and joystick control

The emulated C= 264 keyboard is mapped to its original place wherever it was
possible. If that does not suit you, select symbolic keymapping from the
input setup dialog window. It will map the symbols (also shift-ed ones)
found on the real plus/4 keyboard to their equivalents of your PC keyboard
locale. Note that the 2 Shift keys on the PC keyboard act differently: left
shift only applies to the PC keyboard while right shift also to the emulated
machine if you are accessing a key that is shifted on the PC's keyboard.

DirectInput and MessageQueue input methods both are applying positional
keymapping. DirectInput is recommended and you should only use the
MessageQueue if DirectInput fails for some reason. Positional mapping may be
annoying at first if you're not used to the plus/4 keyboard, but it comes
handy for keyboard control in games that rely on the physical positions of
the keys. Here are the positional mappings of a couple of special keys
(these are mostly valid in symbolic keymapping mode, too!):

plus/4 PC

ESCAPE: ` (tilde)

COMMODORE: left Ctrl

CTRL: right Ctrl or Insert (for



HOME: Home


INS/DEL: BackSpace

CURSOR PAD: cursor keys


These are the key mappings when the josytick is emulated through the PC

JOYSTICK MOVE: cursor keys or numpad
2, 4, 6, 8 (selectable via the Input dialog window)

JOYSTICK FIRE: numeric 0

Select 'Joystick emulation' from the 'Settings' submenu to plug the virtual
joystick to the numeric keypad and the numeric 0 key. If you do not succeed
try 'Swap joystick' (or press ALT+J), this will switch between joystick port
1 and 2. Tick the 'Use PC joystick' option in the dialog window, if you own
a PC jopystick and want to use that for joystick emulation. The recommended
input setup is DirectInput, as it allows more accurate input handling while
at the same time uses less system resources.

Disk drive support

Currently three kinds of drives are supported: the 1541, 1551 and the 1581.
In the future there might be more exotic drives supported, but the available
software for them is very limited, so the priority is low.

1541 drive emulation (CPU)

The 1541 is a well-known device also compatible with other Commodore
products, like the popular C64. This mode sports a full-blown 1541
emulation together with a 1 MHz 6502 CPU, the 2 VIA-6522 chips and the
floppy disk controller, disk rotation etc. Custom loaders are therefore
also supported. The D64 files are first converted to GCR format and
buffered by the emulator internally for reading. Writing is also
implemented. If you encounter turbo loaders that fail, you may attempt
enabling a built-in hack by pressing Ctrl+Alt+X that will circumvent a
necessary half-cycle accuracy for now.

One can also select parallelized 1541 drive emulation, although the
available software for it is rather limited.

You can debug the drive from the external monitor (see chapter 'The
external monitor' later).

1551 drive emulation (IEC and CPU)

The 1551 is a high-speed parallel drive specifically made for the
264-series. It has a proprietary interface called TCBM that has not been
used in any other Commodore products. The 1551 emulation has two modes:
IEC and CPU. The first one is not real disk drive emulation. Disk commands
are caught on the parallel bus and intepreted by the emulator itself, so
actually the behaviour of the DOS is simulated. Advantage is that it has
virtually no overhead compared to a true drive emulation, disadvantage is
that custom disk loaders will not work with it. The 1551/CPU mode aims to
emulate a full 1551 drive together with the 2 TIA chips, 2 MHz 6510T
processor, 555 astable multivibrator for IRQ and the disk drive mechanics
(that is actually the same as that of the 1541). As a consequence, it's
the slowest drive emulation mode, while in turn all possible custom
loaders should work fine (in due time).

1551/IEC has support for only two device numbers 8 and 9. This limitation
is caused by the architecture of the TCBM bus and not a shortcoming of the
emulator. In this mode also high speed write operations and T64 images are
supported. Almost the full DOS is supported, except for:

  • REL files

  • B-E (block-execute) and M-E (memory-execute)

  • overwrite command (@)

Note: the option 'Set drive folder' only affects the 1551/IEC emulation
when no D64 files are attached (on startup or after a 'Detach D64' is
selected from the File menu). It sets the current folder for the 1551 and
it will be used for disk save and write operations. The possibilities are
limited when using a folder as a drive, as it may not have blocks for

1581 drive emulation (CPU)

The Commodore 1581  is a 3½ inch double sided double density floppy
disk drive made by Commodore primarily for the C64 and C128, although it
is compatible with the 264 series as well since it is using the CBM serial
bus. The drive stores 800 kilobytes using an MFM format different from
both DOS (720 KB), and the Amiga (880 KB) formats. The 1581 provides a
total of 3160 blocks free when formatted (a block being equal to 256
bytes) and also implements subdirectories. Its native image format on
emulators is the D81. The D81 image files pertaining to this drive are
read/writable in the emulator. This mode sports a full-blown 1581
emulation together with a 2 MHz 6502 CPU, the CIA chip and the WD1772
floppy disk controller, but no disk rotation atm. Custom loaders are not
known to exist but are in theory also supported to a certain degree.

Printer support

The Commodore serial printers are supported through the serial IEC
interface, both as device 4 and 5. This includes printing to raw and CR/LF
corrected ASCII dumps as well as bitmap with the MPS-803 printer on an IEC
protocol level and a CPU level emulation of the MPS-802, though the latter
has a few known issues and only works with bitmap file as target. The path
of the target output file can be specified through the printer setup
dialog window. Also, custom character ROMs can be specified for these

Tape device support

There's read/write support for low level raw tape images commonly known
as the MTAP format. Loading a TAP image's content is simple: you can do it
via the 'Autostart image' option or thru the Tape menu by selecting
'Attach TAP'. If you choose for the latter, you have to make sure that you
type the appropriate BASIC commands for tape loading: LOAD"",1,1 . Then
press F5 to start the tape. If you have the Quickdebugger selected from
the Screen menu you can see as the the emulator advances in the file.

Creating TAPs is  a bit more complicated. Firstly: you can only
create new TAP files, can not append to existing ones or overwrite them.
To create an empty TAP image, select 'Create TAP' from the Tape menu. You
can select between wholewave and halfwave format by ticking/unticking this
option in the file dialog window. The wholewave format is about half the
size of the halfwave one, but is less compatible with all the turbos. As
the 264 family's tape interface is edge-triggered, rather than
level-triggered, there are more possible waveforms than on the Commodore
64 for example. You must not attach the newly created TAP again! When you
typed SAVE from the emulated machine you can press the RECORD button by
selecting it from the Tape menu or pressing SHIFT+F6. When finished
saveing make sure you detach the TAP you've just written and reattach it
before trying to load as the 'Detach' option puts some very important
information into the TAP header which you miss you may be unable to use
your TAP elsewhere.

Alternatively you can load 8-bit digitised WAV or RAW samples to the
emulator. It is however not encouraged as is having a lower sample
frequency than the MTAP while taking up to about 8 times more disk space.
The advantage is that you can create working WAV/RAW samples without any
special hardware if you're lucky enough.

The external monitor

YAPE has a simple external monitor which you can use to track the
internals of the emulated machine. You can enter the monitor by pressing
ALT+M or selecting 'Monitor' from the Machine menu. The monitor is
console-like that is you have to type in commands and press ENTER. Limited
editing functioanlity within the command line is also supported (cursor
left/right, BACKSPACE, command history etc.). You can also enter the
monitor explicitely either by reaching a breakpoint (set from the monitor)
or a crash instruction (in the latter case you are prompted with a
confirmation dialog window first).

The monitor features:

  • almost all functionality that can be found in the TEDMON (the 264
    famliy's built-in machine code monitor)

    • display memory contents (M)

    • change memory conents (>)

    • transfer memory contents (T)

    • hunt memory for a certain byte (H)

    • fill memory with a certain byte (F)

    • compare memory areas (C)

    • disassembly (D) : this can be redirected to an external file if you
      give the 3rd parameter as a file name

    • display CPU registers (R)

    • go command (G) : sets the PC of the CPU to the selected address

  • debug the CPU (Z) : depending on the actual context, it'll show and
    execute the next opcode of the selected CPU

  • debug step over command (Y): same as above, but JSR commands will not
    be followed

  • advance 1 or more system bus cycle (S) : without a parameter it will
    advance one system bus cycle (there are 114x312 cycles per frame in the
    264 family) If a parameter is given, it'll advance the number of cycles

  • breakpoint support (B) : by providing an address as an argument, the
    machine (or drive) CPU will be set to jump into the monitor when the PC
    reaches the address given. In case a 3rd parameter is provided, this
    will be a memory watchpoint for a combination of R for READ, X for
    EXECUTE and W for WRITE. Note that watchpoints halt the CPU *after* the
    instruction. This feature is also supported for the emulated drive's
    CPU. Once set, you can turn it on/off by typing B followed by the
    address as parameter. By simply typing 'B', Yape will list all
    breakpoints/watchpoints along with their corresponding types (read,
    write, execute).

  • context switching between the drive and the machine if true drive
    emulation is selected (W). If it's followed by a device number, Yape
    will switch to that device's (drive's) context.

  • '@' will toggle between the machine's RAM and current ROM banking

You can get a simple help on these commands from the monitor itself by
typing '?'. To exit the monitor type 'X' or simply click the upper left
corner of the monitor window.

Development using YAPE

If you don't own the original hardware or it is not functional anymore, you
may consider developing under the emulator with an approppriate
cross-development tool. Programming information on the 264-family hardware
can be found:

Cross development tools that can be used with YAPE directly:

  • CBM .prg Studio by Arthur

    by Csaba Pankaczy: open source integrated development environment
    using the AS65 or the TASM compilers

  • AP4 by Zoltán Péter:
    assembler and IDE in one, discontinued


A number of people helped me during development either by providing
hardware information, testing or user hints. Thanks to:

  • Csaba Pankaczy, Luca Carrafiello and Mike Legg for pointing out bugs,
    tips and some code in the monitor, and all their work on 'plus/4 world'

  • Levente Hársfalvi for reverse engineering the sound hardware, sampling
    the noise output, writing the HP/LP filters, some TED and oscilloscope

  • Zsolt Prievara, Mike Dailly, Tibor Biczó in helping me getting
    familiar with emulator programming and the plus/4 hardware during the
    early days of development

  • Markus Brenner for his help implementing the MTAP support

  • Marko Mäkelä for his advices with the CPU and tape emulation

  • Ingo Jache, Valentino Zenari, Balázs Kiss, Vladimir Lidovski and many
    other people for bug reports, testing and tips

  • JoseQ, Navvie, Jim and Joco for hosting

The following information sources were used:

  • The plus/4 mail list archive

  • 64doc by Marko Mäkelä

  • 'A Commodore plus/4 belső felépítése', 1988, Novotrade Rt.

  • TED preliminary data sheets (7360R0)

  • TIA 6523 data sheets

  • VIA 6522 data sheets

  • CIA 8520 data sheets

  • Christian Bauer's VIC-II article

  • Inside the C= DOS

  • Circuit diagram of the 1541

  • Circuit diagram of the 1551

  • Circuit diagram of the 1581

  • Toshiba 6721A speech LSI data sheet

And of course special thanks to all the users and the plus/4 sceners who
helped and encouraged me during all the years! Kudos for all those nasty
demos that failed or still fail to run properly! Keep up the good work,
and keep the scene alive! Cheers!


If you like YAPE you may wish to check out my other emulator projects:

  • 'yapeSDL': is an incomplete open source SDL2 port of YAPE with
    Commodore 64 emulation as well. Link:

  • 'tedplay': is a Commodore format music player supporting SID, C8M and
    PRG files. Link:

  • 'HoLa!': it emulates a Hungarian 8-bit micro called HomeLab, the
    "Hungarian Apple ][". Find it at:
    (in Hungarian only).

  • 'HT1080Z': a System-80 emulator. It is a very similar machine to the
    TRS-80 Model I Level 2. Homepage (in Hungarian):

  • 'Ultimo': it emulates a Hungarian 8-bit microcomputer called Primo,
    manufactured between 1984 and 1986. Find it at:
    (in Hungarian only).

  • 'WinTVC': it emulates another Hungarian 8-bit micro called TV
    Computer, very similar to the ill-faited Enterprise 128, manufactured
    between 1986 and 1989. Find it at:
    (in Hungarian only).

  • My own homepage that hosts all
    the above emulators at one place.

Copyright © Plus/4 World Team, 2001-2018