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PC Interface

If you no longer own (or have connected) a real Commodore computer but you long for the simplicity and fun of those 8-bit computers, then I recommend you look at VICE. It is a free, open-source, cross-platform emulation of most Commodore 8-bit computers such as

  • CBM-II (PET)
  • VIC-20
  • C64
  • Plus/4
  • C128

It offers good (cycle-exact) emulation on a modestly powered PC (runs fine on 333MHz Pentium II). Besides the computers themselves, the disk drives (1541, 1571, 1581, et al) and various hardware expansions (RAM expansion unit, cassettee, modem, and even ethernet) are emulated. Naturally you can also use your PC's mouse and joystick where approriate (i.e., if the software you run can use it). Unlike some other emulators, VICE is still actively being developed. Did I mention it's free?

Disk Images  

When using an emulator, you (and the emulated machine) will need a way to access the files needed by your programs. Most emulators offer the ability to access data on your hard drive just like your operating system (DOS, Linux, Mac, Windows) but many programs on the emulated machine want to access data on a specific disk format with a specific interface (typically a C1541 disk). So disks are also emulated as 'images' (not a 'picture' but a special file structured similar to the data on a real disk). The most common disk image for Commodore emulators is the '.D64' for C1541 disks; other types include '.D81' for C1581 disks and '.T64' for cassette tapes.

And there are more types too. Not just because other devices exist, but also because different ways of emulating the disks exist. Consider a 1541 disk. A .D64 image is often sufficient but some programs store or retrieve data in non-standard ways that the .D64 can not possibly represent accurately. So there is a disk image type called .G64. This type encodes data, like the 1541 drive does, using GCR (group code recording) and includes all the stuff normal programs never need, like sector headers, checksums, intersector gaps, and sector interleave.  Consequently, a .G64 disk image is much larger than a corresponding .D64 disk image.  Because only some special copy-protected software needs all that extra data, .G64 disk images are rare. 

  Working with data images  

To work with data on these, you can use the emulated Commodore computer and software written for it. But those 8-bit computers were slow and the serial communication with the disk drive is even slower. Tape drives are slower still! It is usually much faster and more convienient to work with data outside the emulated machine. There are several programs available for that.

VICE comes with a program called 'c1541'. This is a command-line program to be run in a dreaded (for most Windows users) DOS Box. It does its job well and operates on many image types. Nice for the occassional file, or when using a less common image type. Another possiblility for exotic image types is DskCenter. When working with a lot of files, it helps to visualize things so a GUI is often preferable. Several such windows-based programs are available.

D64 Lister is a nice program to work with .D64 disk images. Supports upper and lower PETSCII, GEOS files, BASIC files, and of course disk editing. It is not open source nor does it offer editing image types except .D64.

D64 Editor is another editor mostly for .D64s but it has some experimental .T64 features too. This one is open source, Visual BASIC.

To be continued....

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