With the success of the VIC-20 and the 64, Commodore decided it was time to introduce a more powerful version of BASIC, to the average user. They were also working hard to claim a larger share of the Business and Educational markets. So, in 1984, the Plus/4 was introduced as the Commodore "Productivity Machine". With built-in software, advanced graphics and smaller size, it seemed to be the ideal machine for the average small business and home. Indeed, it might have meet those objectives and claims, if introduced a bit earlier. Unfortunately, for the Plus/4, by this time most folks were familiar with the feel of the 64 and had come to expect the sound and graphics that it's games had to offer. With this condensed history in mind, let's take a look at what the Plus/4 was designed to do, what it will do and why it was forgotten. First of all, the Plus/4 was never designed as a "downgraded 64" and was never designed to replace the 64. Commodore knew that some people would prefer the 64, but hoped that some would like this new machine. Each machine had it's own advantages (and disadvantages). The Plus/4 was designed especially for easy programming of application software. The built-in software was a bonus, for the small business and first time user. This software, on internal ROMs, was actually pretty good in that day and time. The word processor was easy to master, the spreadsheet was similar to LOTUS 1-2-3 and the file manager was very handy. These were custom designed by some of the best talent available. The 60000+ byte of memory, available for BASIC, had many programmers doing some very mental things. Additionally, several alternate programming languages were available, on ROM, for use in the Plus/4. This last, was one of the very things that contributed to the Plus/4's demise. Originally designated the 264, the Plus/4 contains all of the BASIC 4.0 disk commands except for DOPEN, DCLOSE and RECORD. Many new commands like RENUMBER, TRAP, RESUME and KEY, were seen on a home computer for the first time. Along with the enhanced commands there was also included a versitile ML Monitor. It's sister, the 364V (shown, but never released) also sported a keypad and built-in speech software. A new high speed parallel disk drive, the SFS-481, was especially built for this new line of Commodores. With a data transfer rate of several times that of our present 1581, it was the cat's meow. The 7501 microprocessor, in the Plus/4, has a clock speed of 1.76 MHZ. The sophisticated method for bank switching allows it to choose from any one of four 32K ROMs at a time. The cartridge slot can access up to two 32K ROM programs and additional 32K ROMs can be "piggy-backed". At the 64's RS-232 port, the use of software to emulate an ACIA chip, limits it's baud rate. The Plus/4 contains an actual ACIA chip, which allows communication to take place at speeds as high as 19,200 baud. Extra chips were available to change BASIC to LOGO, PILOT, FORTH, Pascal, COMAL, PROMAL and a version of C. Unfortunately, at this time, many Commodore dealers were simply unwilling to give up any shelf space dedicated to the hot selling 64, for a new machine. Also, most dealers refused to stock the additional "language" ROMs, telling Commodore they were too busy to be swapping chips. That was unfortunate, as very few of those chips survived to be found by present, Plus/4 users. Of course, there were a number of other obvious incompatibilities. The cassette port used the new European mini-DIN plug, as did the joystick ports. Finally, the Expansion port used a 50-pin connector, so 64 cartridges will not work with it. For the first time, since 4.0 for the PET, Commodore acknowedged the importance of the disk drive. The command structure in the Plus/4 is designed for disk operation. Commands such as BACKUP, COLLECT, DIRECTORY, COPY, DLOAD, DSAVE, HEADER, RENAME, and SCRATCH are all included. The Plus/4, on powering up, defaults to a disk drive. Using the Commodore and Run/Stop key combination on the Plus/4 will cause it to load the first file on a disk. Whatever faults one can find with the machine itself, you really can't fault it's BASIC. At this point, please allow me to degress a bit and explain the point of this series of articles. They will not be written to defend the Plus/4, but to provide you with as much information as I can. Hopefully they will make it easier, for those of you that have a Plus/4, to wring the maximum out of your machines. Maybe those of you that have been using one as a doorstop, will dust it off and take another look. There are many of these machines available at swapmeets, selling for just a few bucks. I hope to show you, the user, that there is still some mileage in these old machines and a couple of areas in which they are very useful. I'd like to cover the areas of high-speed data transfer ( I've been using a modified IBM pocket modem, on mine for years) and the modification and changing of the internal ROMs. This last is greatly simplified by the fact that the major chips are all socketed, in the Plus/4. I'll try to touch on many new areas of uses and programming the Plus/4, both in BASIC and ML. We'll go into the Graphics and Sound areas, on the Plus/4, and get into custom character sets. There'll be a discussion, for those of you with a C-16, of how to upgrade it to 64K of memory. We'll look at banking and the similarities here, between the Plus/4 and Commodore's alpha prototype, the C-65. We'll cover the switching of the ROM version 6 machines, and it's cousin in the C-65, between PAL and NTSC video format. We will work with some of the missing alternate language ROMs and provide you with the necessary data to create them! Finally, we'll end this series with the construction of a utility ROM cartridge with a number of useful programs, utilities, Graphic and ML toolkits on it. This will require a pair of 27128 EPROMs. Ofcourse, I will supply RAM versions for you to try. There are a number of decent Plus/4 program libraries available. Jack Vander White, here at COMMODORE CEE, has one! Much is new stuff and quite a change from the days when there was very little software, to be had, for the Plus/4. My own library is now approaching 4000 files. Many of these newer programs are written with C64 and C128 companions. That is because I am also a dedicated C64 and C128 user. So, why don't you come along for the ride... even those of you that don't have a Plus/4. It should provide you with some interesting insights into the origins, of your own favorite machine, and might even give you a few good chuckles! -----------------------------------