By Bob Carmany

A RAMdisk in the functional equivalent of a physical disk drive without the moving parts. A physical disk drive system stores data on a mylar disk with a coating of iron oxide. The data is retrieved by a read/write head that is controlled by a stepping motor as the disk spins in its protective cover.

A RAMdisk stores data on a series of static RAM chips that have been divided into sectors similar to the arrangement on a physical disk. However, since there are no moving parts, the RAMdisk is much faster than a physical disk drive and the data is available almost instantaneously.

Loading a RAMdisk The two surviving modern RAMdisks (QUEST and HORIZON) are battery-backed to ensure that the data is maintained even after the computer and P-Box are turned off. Each is powered by three 1.25V NI-CAD batteries that charge whenever the computer and P-Box are turned on.

Both come with a software package that allows the user to initialize, partition and assign drive numbers to the RAMdisk. The first step is to load the generic DSR (Device Service Routine) into the RAMdisk. This allows the computer to find the RAMdisk. Each of the configuration program is menu-driven and very easy to follow. The only limitation is that a single disk drive cannot exceed the maximum size of 1600 sectors (ie. 400K). Let's assume that we have a 512K RAMdisk installed in a system with a TI Disk Controller.

Once the RAMdisk has been initialized, the configuration program will ask for a drive number and size. It is wise to assign a drive number greater than the maximum number of drives that your physical controller can handle (ie. 4-9 for a TI Controller and 5-9 for a Corcomp Controller) to avoid any conflicts.

We can designate part of our RAMdisk as DSK4 (1600 sectors) and the other part as DSK5 (448 sectors) which fill up the entire 512K (512*1024/4 sectors per kilobyte = 2048 sectors).

Each of the RAMdisks come with a menu-type programs, MENU for HORIZON and AUTO for QUEST, that are variants of the John Johnson BOOT program. These can be configured to allow for the loading of both XB and A/L programs available when the system first boots. In each case the menu program intercepts the TI startup routine and slaps the user-defined menu in place of the title screen. They come with full instructions.

In addition, there are user defined CALLs that can be invoked to either directly load A/L programs from the command mode or CALL them from a running program. There are simple instructions for there use as well.

When you are through, the generic DSR has been modified to the users configuration and installed into the RAMdisk. It should now be saved to disk under a different name than the original.

At this point, you are ready to load whatever programs you wish into your RAMdisk. This can be done with ANY disk manager program. Oh yes, you can write protect either or both parts of the partitioned RAMdisk and enable or disable the MENU/AUTO program.

Common problems There are two problems that arise with RAMdisks that can be perplexing at times. They are easily curable.

If the RAMdisk will not load programs and a check with a disk manager indicated that the RAMdisk is "not there", the DSR has been corrupted. The easiest cure is to go back to the configuration program a reload the saved version of your customized DSR.

If the RAMdisk will not hold programs in memory, the problem is with the battery circuit. This can be a loose battery or a cold solder joint. The easiest way to check to with a voltmeter. Check voltage and continuity.

You can reach me at: 1504 Larson St., Greensboro, NC 27407

FAQ courtesy of Dan Eicher