Dwarf, a Mesa machine architecture emulator for Xerox 6085 and Guam workstations

Dwarf is an emulator for the Xerox Mesa processor architecture with 2 incarnations for emulating different machine generations marketed by Xerox in the 1980-ies and 1990-ies:

• Draco simulates a 6085 workstation (also called Dove or Daybreak) running the Mesa microcode
• Duchess rebuilds the Mesa machine in the GVWin product, which was itself a software emulator running on a PC under MS Windows 3.x

Dwarf is implemented in Java 8 and should therefore run on most systems where the Java 8 and a decent window system is available.

In the tradition of Xerox processor implementations having D as first letter (Dolphin, Dorado, Dicentra, Dandelion, Daybreak, Dove, Daisy, ...), the Java software implementations of the Xerox machines have been named Dwarf, Draco and Duchess.

And yes, it is not the first open source software emulator for the Mesa architecture, this merit goes (to my knowledge) to Don Woodward for his Dawn emulator and Yasuhiro Hasegawa for his Guam mesa-emulator.

Quick start

To run Dwarf, you will first need a Java 8 (or newer) runtime installed for your operating system. Dwarf was developed on Linux and tested with Linux-Mint, MS-Windows 7 and 10.

Next you will need the Dwarf software. It is available as ready to run release on Github: download the newest dist.zip package from the github repository, unzip the package, done (more or less).

The archive dist.zip contains the directory dwarf having the runnable jar dwarf.jar and the default keyboard mapping file, as well as a set of sample configuration and shell script files for running some 6085 machine setups with Draco (ViewPoint 2.0 and XDE 5.0) and running XDE (Dawn) and GlobalView (GVWin) environments with Duchess.

And finally you will need the disk images having the Xerox environment to run.

For the Draco 6085 emulation, disk image files for ViewPoint 2.0 and XDE 5.0 are provided in the Github project in directory disks-6085. The 6085 disks readme in this directory describes the environment installed on each disk and how to setup the environment with the sample configurations.

For the Duchess emulation you will need a bootable virtual disk having a Pilot 15.3 based Xerox operation system installed and a compatible germ file. This can be the XDE disk provided by Don Woodward on his site for his Dawn emulator or a GlobalView 2.1 disk:

• for XDE see the Don Woodwards Dawn emulator page: the page provides links to the compressed Dawn.dsk file and to the source package for Dawn, where the Dawn.germ can be found in the directory Source/Dawn/Resource.

• for Globalview (the successor to ViewPoint as successor to Star), you can use the disk image file of your GlobalView 2.1 installation (usually C:\GVWIN001.DSK) along with the germ file (usually C:\GVWIN\GVWIN.GRM).
  If no GlobalView disk is available, ready to run MS Windows 3.1 environments with GlobalView can be found at the archive.org, e.g. gvwin.zip or win3_globalview_21.zip.

To set up such a Duchess system, copy the disk image file and the germ file into the corresponding directory of the sample environment and verify that the names match the expected ones in the configuration files (for XDE: Dawn.dsk resp. Dawn.germ, for GlobalView: GVWIN001.DSK resp. GVWIN.GRM)

Enough theory, here are screenshots of the emulator running some of the Xerox environments mentioned above.

Duchess running GlobalView 2.1 in color mode (sample script duchess-gvwin-color[.sh]):

Draco running the XDE 5.0 with hacks disk (sample script draco-xde5.0+hacks[.sh]):

Draco running the ViewPoint 2.0 disk (sample script draco-vp2.0.5[.sh]):

Working characteristics of Dwarf

Besides a mesa processor, Dwarf supports the following peripherals found on a Xerox workstation:

• real memory

  • Draco: fixed to 2048 kwords (4 MiB)
  • Duchess: configurable in exponential increments between 256 kwords (512 KiB) and 8192 kwords (16 MiB)

• virtual memory

  • Draco: fixed to 16 Mwords (32 MiB)
  • Duchess: configurable in exponential increments from real memory size up to 32768 kwords (64 MiB)

• bitmapped display rendered in a Java Swing window

  • Draco: small (832x633) or large (1152x861) 6085 black&white screen
  • Duchess: black&white or (8-bit) color display in configurable size or as fullscreen display,

• keyboard (with configurable mapping for Xerox specials keys)

• 2 or 3 button mouse

• one harddisk image
  (specific file formats for Draco and Guam, as 6085 and Guam disks have different internal structures)

• one floppy drive, image file changeable at runtime

  • Draco: IMD/DMK floppy image format of 6085 (5.25") floppies (read/only)
  • Duchess: 1.44 MByte raw (read/write) or legacy IMD/DMK floppy images (read/only)

• network device, interfacing to a Dodo NetHub or as fallback to an internal time service

Dwarf supports the following floppy image formats:

• IMD for floppies if the file extension is .imd (case-insensitive)
• DMK for floppies if the file extension is .dmk (case-insensitive)
• raw format for 3.5" floppies as created by the original emulator on PCs

The term "legacy floppy" for Duchess means that the image was created from a floppy disk written by a 8010 (8" floppy) or a 6085 (5.25" floppy) workstation with a Pilot based OS like XDE (4.0 or later) or ViewPoint (1.0 or later). The disk content of the legacy floppy image is implanted in a template 3.5" image based on the XDE sector layout. This allows to read the legacy floppy content. Legacy floppy images are mounted in R/O mode, as changes cannot be written back into the original format (IMD or DMK).

When using or thinking of using Dwarf, some characteristics of the implementation should be kept in mind:

• Dwarf loads the complete virtual hard disk into main memory, performing all disk operations in memory. When (and if) the system is shut down normally, the modifications to the hard disk are written to a compressed delta file containing the differences to the original disk, which stays unmodified. When the same system is next started, Dwarf first reads the original disk and applies the delta in memory.
  This approach gives fast disk I/O, but possibly requires increasing the Java heap space for large disks (however a "normal" Pilot disk (under 80 MByte) plus 16 MByte real memory can be used with Java defaults)

• similarly Dwarf loads a complete virtual floppy disk image file into memory for diskette operations.
  In case of a raw (1.44 MByte) floppy image mounted in Duchess, when ejecting the floppy or shutting down the machine, the complete floppy image file is overwritten if the floppy was modified (no delta file). Legacy IMD or DMK floppies are always mounted read-only and are not written back, as only reading IMD or DMK files is supported.

• unlike Xerox machines, Dwarf is not a microcoded machine, so Dwarf will only execute the Mesa instructions; running Lisp or Smalltalk or Cedar environments (would these be available) by loading a different microcode is not possible.

• Dwarf supports networking by connecting to a Dodo NetHub, allowing to interact with network elements connected to the same NetHub, these can be other emulated Xerox machines, a Dodo server providing XNS services or a "real" network with the NetHubGateway (see Dodo Services - XNS with Java).

Running Dwarf

Besides having the Dawn program installed (mainly a simple runnable Java jar file) with the disk and germ files, a configuration file defining the characteristics of the machine to run is needed.

Installing or building Dwarf

Dwarf is available as ready to run release on Github (file dist.zip in the github repository). See the above section "Quick start" for the installation of the package.

Hint: the disk or floppy files should not reside in the same directory as the dwarf.jar file, as the Java runtime will high probably enforce the read-only access to files in this directory.

For building from source, download the ZIP or clone the Dwarf Github repository, this gives you a project directory that can be imported into Eclipse (Neon release or newer). The main Java class for the Run Configuration is: dev.hawala.dmachine.DwarfMain

Defining the configuration of a Dwarf machine

A Draco or Duchess machine is configured with a conventional Java properties file, so the name-value separator is the = character and comments are introduced by a #.

Due to the specifics of the emulated hardware peripherals, Draco and Duchess have specific properties for their respective components, however sharing a set of common properties. The following sections first describe the common properties and then the specifics for Draco and Duchess. Looking at the comments in the sample configurations of the distribution package may also be helpful here.

The following configuration parameters can or must be used for machines emulated with Draco and Duchess :

• boot
  the filename of the boot disk; this must specify a disk file in the correct format for the emulated system, i.e. a .zdisk file with a compressed 6085 disk image for Draco resp. an (uncompressed) .dsk file for Duchess; the emulator will automatically load the current delta file for that disk type
  required

• switches
  the boot switches to use
  optional, default: 8Wy{|}\346\347\350\377

• keyboardMapFile
  the name of the keyboard mapping file to use; see the syntax description at the beginning of the sample mapping file kbd_linux_de_DE.map
  optional, default: none (if not given, a minimal mapping for a german keyboard is used)

• xeroxControlKeyCode
  the key code for the modifier key to be used for generating the special Xerox keys not available of a contemporary standard keyboard; the value can be given as hex code introduced by 0x or as the Java key name (VK_...)
  optional, default: 0x00000011 (VK_CONTROL)

• resetKeysOnFocusLost
  if true the keyboard state will be reset to "no keys pressed" when Dwarf loses the input focus; when false the keyboard will not be reset. Resetting all keys to "up" is useful when changing the current window with Alt-TAB, as the Alt-key is a special key on a Xerox keyboard.
  optional, default: true

• processorId
  the processor or machine id for the Dwarf machine (or MAC address in todays wording)
  (if networking is used, it should be ensured that all machines on the network have an unique processor id, or Pilot-based machines will stop by entering 0915 state)
  Attention: the processor id is crucial when running ViewPoint, as the "Software options" available in the ViewPoint installation are bound to this id, so running the same disk with a modified processor id will invalidate the available software
  optional, default: 00-1D-BA-AE-04-C3

• title
  the text to display in the title bar of Dwarfs window
  optional, default: value of the property boot (the boot disk name)

• oldDeltasToKeep
  the number of deltas to keep in addition to the current delta; when saving a new delta, Dwarf renames the now previous delta using the its save timestamp and deletes the older backups count exceeding oldDeltasToKeep
  optional, default: 5

• initialFloppy
  the filename of a virtual floppy file to load in the floppy drive before starting the engine
  optional, no default (no floppy initially loaded)

• floppyDirectory
  the directory-name to use as starting point in the file selection dialog for the insert floppy function
  optional, no default (platform dependent, probably the home directory)

• netHubHost
  the name of the NetHub host to connect to or empty if no NetHub connection is to be used
  optional, default: empty (i.e. no NetHub connection = no networking)

• netHubPort
  the port where the NetHub is listening (must be in range 1..65535) or any invalid port number (e.g. 0) for no NetHub connection
  optional, default: 3333

• localTimeOffsetMinutes
  time zone parameter for the internal time service if no NetHub is used: difference between local time and GMT in minutes, with positive values being to the east and negative to the west (e.g. Germany is 60 without DST and 120 with DST, whereas Alaska should be -560 without DST resp -480 with DST)
  optional, default: 0 (i.e. GMT)

• autostart
  the boolean value truelets the machine start automatically after building up the Dwarf UI; by default, the Dwarf machine must be started manually with the Start button in the toolbar.
  optional, default: false

• autoclose
  the boolean value true lets the Dwarf UI automatically close when the Mesa processor is stopped and after changes made to the disk (and possibly to the floppy) have been saved.
  optional, default: false

• xdeNoBlinkWorkAround
  work-around for the blinking "Time not set! Create no files!" text in the HeraldWindow instead of the current date/time.
  (this blinking text is used if the current time is not in a certain time frame starting with the build-time of the Tajo/CoPilot-bootfile)
  The work-around is to fake the current time to a date in this time frame until the HeraldWindow has probably checked the time and then get back to the real time; the delay for the reverting to the real time is given as number of instructions, expressed in 100.000 executed instructions.
  The value is given as <100thousand-instructions> : <iso-date>
  optional, default: (none)
  the following values usually work:
  xdeNoBlinkWorkAround = 110 : 1987-06-01 for Tajo 12.3
  xdeNoBlinkWorkAround = 150 : 1987-06-01 for CoPilot 12.3
  xdeNoBlinkWorkAround = 150 : 1987-06-01 for Tajo 12.3 + Hacks
  xdeNoBlinkWorkAround = 81 : 1995-06-01 for Tajo 15.3 (Dawn)

The following configuration parameters are specific for Draco (6085) machines:

• fallbackGerm
  germ file to use if the germ cannot be loaded from the 6085 disk image.
  Draco tries to load the germ from the disk, but may fail in doing so (no germ on the disk or the germ is not stored in contiguous sectors): the germ file specified here will be used as fallback
  optional, default: (none)

• largeScreen
  this boolean value defines the screen size for the emulated 6085 workstation, choosing between a large display (19" screen with 1152x861 pixels) or a small display (15" screen with 832x633 pixels)
  optional, default: true (large screen)

• stopOnNetDebug
  this boolean value specifies if Draco will stop the machine when the system enters the "wait for network debugging" state (MP 0915) or if it will effectively wait for a debugger to connect
  optional, default: true

The following configuration parameters are specific for Duchess (Guam) machines:

• germ
  the filename of the germ file
  required

• addressBitsReal
  number of address bits for the real memory, this must be a value between 18 ad 23, giving between 256 kwords (512 kByte) and 8192 kwords (16 MByte)
  optional, default: 22

• addressBitsVirtual
  number of address bits for the virtual memory, this must be a value between addressBitsReal and 25, allowing up to 32768 kwords (64 MByte)
  optional, default: 23

• displayWidth
  the width of the mesa machine display in pixels, must be a multiple 16
  optional, default: 1024

• displayHeight
  the height of the mesa machine display in pixels
  optional, default: 640

• displayTypeColor
  boolean specifying the display mode for Duchess: the value false specifies a monochrome display (default), while true specifies the display as 8-bit deep color display (with a color lookup table controlled by the OS running in the mesa machine);
  setting this option to true is intended for running GVWin 2.1, although the Dawn/XDE disk also works with color mode (not showing any colors however)
  optional, default: false

The following sample properties dawn.properties defines the emulated machine for running the Dawn disk with Duchess:

#
# sample Duchess configuration for Don Woodward's Dawn xde system
#

# title to display in the main window
title = Dawn XDE

# disk, germ and switches for booting
boot = dawn_xde/Dawn.dsk
germ = dawn_xde/Dawn.germ
switches = 8Wy{|}\\346\\347\\350\\377

# boot the disk when Duchess starts
autostart = true

# machine-id (aka. MAC address) of the machine
processorId = 10-00-FF-12-34-46

# screen size of the machine
displayWidth = 1024
displayHeight = 640

# virtual and real address sizes
addressBitsVirtual = 23
addressBitsReal = 22

# definitions file for keyboard mapping
keyboardMapFile = keyboard-maps/kbd_linux_de_DE.map

# default location for floppy image files
floppyDirectory = dawn_xde/floppies

# network configuration, uncomment to use NetHub
netHubHost = localhost
netHubPort = 3333

# internal time service as network fallback: time zone offset to GMT in minutes (negative => west, positive => east)
# Germany with DST => +120 ; Alaska => -480 
## localTimeOffsetMinutes = 0

# work-around for blinking "Time not set! Create no files!" text in the HeraldWindow
# (may need fine-tuning for the instruction number in 100.000 insns)
xdeNoBlinkWorkAround = 81 : 1995-06-01

Command line parameters for Dwarf

Dwarf is packaged in a runnable jar file (dwarf.jar) and started with

java -jar dwarf.jar -draco|-duchess parameters

The first command line parameter defines the machine type type to emulate.

The following additional parameters are valid both for Draco and Duchess:

• configuration-properties-file
  the properties file for the Dwarf machine; if the filename given does not have the .properties file extension, it will be added to the given name
  required

• -run
  start the Dwarf machine, overriding the autostart parameter in the configuration file
  optional

• -v
  dump the parameters loaded from the configuration file before building up the Dwarf UI.
  optional

• -logkeypressed
  log the key press events to the console, issuing the hexadecimal extended key code and if possible the symbol name corresponding to that key; any of these values can be used in a keyboard mapping file.
  optional

• -merge
  instead of running the mesa emulator, merge the current delta for the boot disk into the harddisk image file; the current disk file, the delta and all backup deltas are archived into a zip file (named after the disk file and the current timestamp) and all delta files are deleted before doing the merge.
  optional (as alternative to running the mesa engine)

• -autoclose
  giving this option has the same effect as setting the option autocloseto true in the configuration file, so the Dwarf UI will automatically close after the Mesa processor is stopped and changes made to the disk (and possibly to the floppy) have been saved.

When running the Duchess emulator, the following command line parameters allows to run the Dwarf UI in fullscreen mode:

• -fullscreen
  if this option is given, the Duchess UI will try to switch to fullscreen mode, that is the UI fills the whole screen and is shown without decorations, so the mesa machine display takes the whole space between the button bar at the upper border and the status line at the lower border of the screen (see below). If the fullscreen mode cannot be used on the window system of the hosting operating system, a normal window will be used with the Mesa machine display having the size specified by the parameters displayWidth and displayHeight.

When running the Draco emulator, the following command line parameters allow to boot the system from the network instead of the disk specified in the configuration (booting form the network requires a well-configured boot service on the XNS network):

• -netinstall
  request the germ and the network installer from the boot service and run this installer in the configured machine

• -netexec
  request the germ and the network executive from the boot service and run this installer in the configured machine

Examples:

java -jar dwarf.jar -duchess dawn -run
(run the virtual xerox Guam machine configured in the file dawn.properties)

java -jar dwarf.jar -duchess dawn -merge
(merge the delta into the disk file for virtual xerox Guam machine configured in the file dawn.properties)

Running a Dwarf machine

The following screenshots show the button bar:

and the status line:

of a running Dwarf emulator.

Button bar

The state of the buttons reflects the possible options, e.g. the "Start" button is grayed and disabled if the mesa engine is already running. The buttons should be self-explaining and display a hint when the mouse stays a while over them.

The Insert button opens the file selection dialog for the floppy image file to load. Virtual floppy files must have have an extension .imd or .dmk for loading a 6085 or 8010 floppy image or any extension but a size of 1440 KiB = 1.474.560 bytes to be accepted in the file selection dialog for "inserting" the floppy. If the R/O checkbox is checked, the floppy will be loaded in read-only mode, rejecting any attempts to modify the diskette. Legacy floppy images are always forced to be loaded in read-only mode.
The Eject button removes the floppy, overwriting the floppy image with the new content if the floppy was modified.

Keyboard

The keyboard mapping can be freely defined through a mapping file, however providing a sensible fallback (at least if you have a german keyboard) if no file is specified.

The probably most interesting information is about the special Xerox command keys not available on modern PCs, which are mapped to keyboard keys by default resp. additionally by the sample mapping file kbd_linux_de_DE.map as follows:

Xerox key	builtin default	kbd_linux_de_DE.map
Stop	ESC	ESC
Open	Ctrl-O	Ctrl-O
Props	Ctrl-P	Ctrl-P
Copy	Ctrl-C	Ctrl-C
Move	Ctrl-M	Ctrl-M
Next	Ctrl-N	Ctrl-N
Find	Ctrl-F	Ctrl-F
Again	Ctrl-A	Ctrl-A
Same	Ctrl-S	Ctrl-S
Undo	Ctrl-U	Ctrl-U
Help	Ctrl-H	Ctrl-H
Center		F2
Bold		F3
Italic		F4
Case		F5
Strikeout		F6
Underline		F7
SuperSub		F8
Smaller		F9
Margins		F10
Font		F11
Special		Alt
Expand		AltGr , Ctrl-Alt

Status line

The status line of Dwarfs emulator window shows the current MP code (maintenance panel code) at the left, followed by some statistics of the running machine (uptime in seconds, number of instructions executed so far, number of disk page reads/writes, number of floppy page reads/writes, number of network packets received/sent).

Halting the running system

The safe way to bring down the guest OS is to use the corresponding function of its UI (e.g. "Boot button" in the "Boot from:" menu in XDE), as this ensures that the OS flushes all buffers (or at least should so) before executing one of the stopping instructions. When the mesa engine stops running, the state of the virtual harddisk and of the possibly loaded virtual floppy is saved to disk.
There are however exceptions with Draco:

• ViewPoint does not have a "stop the machine" option (not in the menu and not as logout option). So for bringing down ViewPoint, log out, wait until the screen turns black with the bouncing keyboard and then simply halt the system with the "Stop"-button (which will save disk changes, see below).
• for the xde5.0.zdisk (XDE 5.0 for 6085) using any of the XDE menus for shutting down the system will produce an unusable disk with Draco (see the 6085 disks readme). A system running this disk must be shut down with "Stop"-button.

Clicking the "Stop" button or closing the Dwarf window while the mesa engine is running will open a confirmation dialog: confirming will do a hard stop of mesa engine by leaving the instruction interpreter loop and then save the current state of the harddisk and floppy. However the OS has no chance to flush its buffers, so the current state of the harddisk is possibly inconsistent and may require a scavenger run on next startup.

Stopping Dwarf externally using the host OS means (Ctrl-C in the shell running the Java program, kill command etc.) will of course prevent writing back the harddisk resp. floppy content, so changes will be lost.

Using the same Guam disk with different emulators

Unlike other emulators for Guam, Duchess does not overwrite the original virtual harddisk file, but saves changes in compressed delta files. This means that the delta must first be included in the harddisk image file (using the -merge command line parameter) before the harddisk file is used with an other emulator.

Not merging the delta has the following effects:

• when running an other emulator with the virtual harddisk, the changes made in Duchess boot sessions will not be visible, as Duchess leaves the original file unchanged

• saving changes to the virtual harddisk file from the other emulator will make the delta files saved by Duchess useless, as the base for the delta changed and will high probably result in a corrupt disk when booting the new base disk file with the delta.
  However removing the delta and starting with only the new base disk should work (if the other emulator was closed regularly) and the changes in the disk will be visible in the Duchess session.

Known limitations

• running Draco and Duchess has currently a "boot once" approach, meaning there is no way to reset or restart the guest OS once it was booted: to restart the OS, the Dwarf program must be stopped and started again

• furthermore other non-vital devices are missing, having only rudimentary agent implementations (tty, serial and parallel ports).

• (Duchess-specific) using (explicitly or implicitly) functionality requiring the StreamAgent to communicate with the "external" world (local file access, local printing, copy&paste, ...) will probably leave the system in an unusable state (hourglass mouse pointer with fast running cpu), as the Duchess agent probably gives the wrong answer for "not available".

Known Bugs

• Draco rigid disk controller: incomplete resp. buggy implementation becoming apparent for disk operations of XDE 5.0 CoPilot when doing world-swaps, resulting in MP 0921 (boot loader device error) resp. unusable disks after shutdown (MP 0915 on re-boot)
  This does however not affect the normal disk operations, as ViewPoint and the XDE 5.0 with 2x Tajo (seem to) work normally with the same implementation.

Development history

• 2025-01-11
  bugfix for issue#12: less restrictive label-check for 6085 disks

• 2022-03-09
  added simple implementation of instruction TRAPZBLT

• 2021-11-05
  added 3 undocumented instructions, apparently introduced by Fuji Xerox (impl. taken from Yasuhiro Hasegawa's Guam emulator)

• 2020-11-24
  added fullscreen support for Duchess (command line option -fullscreen)
  added autocloseconfiguration parameter and -autoclose command line parameter to Duchess and Draco

• 2020-07-05
  introduced the Draco 6085 emulation as second machine type for the Dwarf Mesa machine kernel
  given the name "Duchess" to the Guam emulation (now being the first machine type based on the Dwarf Mesa machine kernel)
  provided Draco disk image files for ViewPoint 2.0 and XDE 5.0

• 2020-05-25, 2020-06-07
  added color display support, allowing to run GVWin 2.1 in 8-bit color mode

• 2020-05-23
  implemented some of the floating point instructions, changed status line font for better rendering on linux-mint

• 2019-05-01
  fixes for BITBLT/COLORBLT, fixes for smaller flaws preventing the correct rendering of the help icon in GlobalView

• 2019-04-26
  bugfix to instructions BYTEBLT and BYTEBLTR, utility program CnvDmk2Imd.java for converting DMK floppy image to IMD format

• 2018-09-16
  added network support by reworking the NetworkAgent for interfacing the NetHub of Dodo Services and use an internal time service if networking is disabled

• 2018-07-17
  added the "-merge" command line parameter (for merging the delta file into the harddisk image file)

• 2018-07-14
  fixes for legacy floppies (reject DOS floppies, improved compatibility with more DMK-/IMD-imaging tools)

• 2018-07-08
  added support for reading IMD and DMK legacy floppies

• 2018-06-26
  keyboard improvements

• 2018-01-09
  made the modifier key for generating special xerox keys configurable, added experimental internal time server

• 2017-12-04
  initial commit to github: First release for Dwarf, able to run Dawn/XDE and GVWin 2.1 as standalone machines

Bibliography

The following documents available in the internet were useful for creating Dwarf and its mesa engine:

• Mesa Principles of Operation, Version 4.0, May 1985

• Mesa Principles of Operation: Changed Chapters

• PrincOps Corrections

• 6085 FE Training

• various documents at Bitsavers, xerox/6085 about the 6085 machine

Acknowledgments/Credits

Special thanks go to Don Woodward and Yasuhiro Hasegawa who implemented Mesa emulator programs and published their work as open source, including their own documentation (see Bibliography). These programs sources and documents were extremely helpful and in fact essential in filling the gaps left by the Xerox PrincOps documents about such "details" as:

• the numeric opcodes for the instructions

• interfacing the peripherals like screen, mouse, keyboard, disk etc.

• undocumented instructions like VMFIND (essential for the Pilot-OS) or COLORBLT

• initialization sequence for loading and preparing the germ to bring a mesa engine in a runnable state as defined by PrincOps for the initial XFER.

Further thanks go to websites resp. museums like Bitsavers, Computer History Museum or DigiBarn Computer Museum (just to name a few!) and the people behind these sites and museums which archive the heritage of the emerging digital age, be it documents, hardware or software, among them also for Xerox systems.

Xerox itself has thankworthy made the Alto software and documentation accessible (hosted by the Computer History Museum, see Xerox PARC Alto filesystem archive), a similar generosity regarding documents and software for the more modern D-machines and successors would of course be welcome.

License

Dwarf is released under the BSD license, see the file License.txt.

Disclaimer

All product names, trademarks and registered trademarks mentioned herein and in the source files for the Dwarf program are the property of their respective owners.