Using the Commodore RAM Expansion Unit by Dick Estel This information applies to the 1764 and 1750 REU's and units that have been expanded to 1, 1.5 or 2 megabytes. GEOS is the only program listed that conveniently makes use of the expanded units (1 meg and larger). Maverick may be modified to use the expanded unit. The expansion normally includes installation of a toggle switch to convert the unit back to the normal 512k. Some of the programs will not recognize the REU at all unless the toggle switch is changed. Remember in every situation where a file is created within the REU or is SAVEd to the REU, it must be copied to a real disk or it will be lost when power is turned off. There are several commonly-used programs that are programmed to utilize the REU: GEOS: GEOS 1.3 and 2.0 will normally recognize the 256k and 512k REU when the program is booted. The REU will appear as a second disk drive icon with the name RAM 1541 (256k) or RAM 1571 (512k). If your REU has been expanded above 512k, you must use the modified version of the configure file (2.1) in order for GEOS to recognize the additional RAM. As far as I know, you cannot use these expanded REU's with GEOS 1.3. CONFIGURE 2.1 is available from many on-line sources and most user group libraries. It is also provided by some technicians when they expand the REU. Refer to your GEOS 2.0 manual for information on using the CONFIGURE program. When used with GEOS, a REU is configured to emulate real Commodore disks drives, as follows: 256k: 1541 512k: 1571 1024k: 1581 Larger REU's emulate various combinations of drives; for example, a 2-meg REU will emulate two 1581's. GATEWAY, the alternative GEOS operating system from Creative Micro Designs, utilizes a larger portion of the RAM and is not confined to emulating actual disk drive sizes. THE WRITE STUFF: If you LOAD and RUN the file RAMBOOT, it will set up the REU to work as if it were a second drive. RAMBOOT then automatically loads BB writer. RAMBOOT is a BASIC program which can be modified to load a file copy utility FC, which then copies files of your choice into the REU. FC may be modified to load the desired files. Complete instructions are found in the TWS manual, as will as in my article "THE WRITE STUFF: 1581 Boot Disk," which will be available at http://home.att.net/~rmestel/commodore.html. The most beneficial use is to place the spellchecker dictionary files in the REU. This allows virtually instantaneous spell-checking of a document. POCKET PLANNER and POCKET FILER: Both these programs automatically recognize the REU as an additional disk drive, into which files may be saved or loaded. The logical use of this would be with Pocket Filer. Entering data in Pocket Filer involves frequent disk access. By placing the data base file in the REU, data can be added in the REU much faster. The updated file must then be copied to a real disk. MAVERICK: Later versions of Maverick will recognize the REU and use it as a storage buffer during disk copy operations. This is particularly useful when using a single (real) drive system; it is possible to copy a disk in two passes instead of the five or six that may be required without the REU. (Copying a 1581 disk with a single drive requires 15 or more swaps!) USING THE REU "ON YOUR OWN:" In order to use the REU in your own programs or to load and save programs, you must run a program that configures the REU as a drive. These programs are available in the public domain, and also are provided on the utility disk that comes with the REU when purchased new from a commercial dealer. Units purchased second hand or through surplus outlets often lack the utility disk. Once the REU is configured as a drive, it works just like any drive as far as copying, loading, or saving BASIC programs. LOAD and SAVE operations are virtually instantaneous. Remember, any file saved to the REU must be copied to a real disk or it will be lost. The REU is used in BASIC programs through three BASIC commands: STASH: Copies a specified block of memory from computer memory to the REU. FETCH: Retrieves a specified block of memory from the REU to computer memory. SWAP: Exchanges a specified block of memory between computer memory and the REU. Use of these commands is beyond the scope of this article and require a knowledge of memory locations and other specifics of programming. A personal comment: For frequent GEOS users, an REU is a virtual necessity. I would also recommend an REU for someone who uses the Pocket Filer with large database files that require frequent updating. For non-programmers who do not use GEOS, the REU is a luxury that may have little practical use.