RAM Extensions


Fortunately, the C64's memory area is seized more than once. Besides its fixed parts BASIC ROM ($A000-$BFFF), Character ROM ($D000-$DFFF), and Kernel ROM ($E000-$FFFF) there's a throughout usable free RAM. Programs like Pagefox, GEOS, or GoDot wouldn't work without this RAM. However, it turned out to be of benefit to extend this memory area. Access to standard storage media (like diskettes) passes off in extreme slow motion compared with access to RAM, even if optimized by floppy speeders.

When the C128 came into use Commodore put RAM extensions on the market, the so-called REUs (RAM Expansion Units). They are three sizes: 1700 (128 KB), 1764 (256 KB), and 1750 (512 KB). Thanks to an own 'intelligence' and to the capability of DMA (direct access to main memory while by-passing the CPU) they are extremely fast and easy to handle. Their capacity can even be extended by putting in more RAM components.

In the meantime GEOS yielded a convenient use for these efficient devices so that other manufacturers offer their own RAM extensions. GEORam had been successful for some time (even without intelligence and DMA). Devices by CMD generally are provided with additional RAM (e.g. RAMLink).

It even was in the early times of C64 that programmers utilized seemingly idle RAM areas of devices that actually should fulfill other tasks. As an example you can attach those 32 KB of a Pagefox hardware module to direct use of a C64, and owners of a C128 - according to the model of their computer - have 16 KB or even 64 KB of additional memory through their built-in VDC RAM which normally is at hand for the display of the 80 column screen.

The most convenient use of these extra memory areas is their use as a superfast disk drive as shown by programs like GEOS, "Maverick", or "Big Blue Reader". This RAM once filled makes you forget all those C64 disadvantages.

GoDot gives support to the expansion devices Pagefox, VDC, and REU. They are administered as a virtual drive 12 by the assistance of devices. During Boot (Ini Files) or rather in the course of working with GoDot (mod..REUTool) RAM extensions can be filled with program modules. Additionally (or at will, according to their capacity; Ini Files), they provide you with space for intermediate storage (Undo, Temp). As access to RAM is so fast, GoDot binds them as system drives, i.e. GoDot will at first display their contents when calling the file requester (see also: mod..FirstDrive).

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Arndt Dettke
god.ADettke@t-online.de

Copyright © 1997, A. Dettke, Last Updated - 07/25/97