software support for memory expansions

From: Marko Mäkelä (
Date: 2001-08-07 16:26:32


I'm sending a copy of this message to the cbm-hackers mailing list.

> I know that Zed for one finds and uses all available memory.  However I
> have not seen a program to enhance a C=64 or C=128 that allows the
> standard units to do the same.

The problem is that the processor only has a 64-kilobyte window (called
address space) to the memory.  If the system has more memory than that,
there must be some way to select a subset of the available memory to the
processor's address space.

The Commodore REU uses copying between external and internal memory, while
other expansions I'm aware of use banking, i.e. they alter the memory
configuration that is connected with the processor's address lines.

> One would think that it is possible to write a wedge type program to
> do this.  Perhaps someone has, but if so have not seen one.

One thing that could be relatively easy to implement is a RAM disk.  One
such utility comes with the Commodore REU.  Maybe it would be possible to
write similar utilities for other memory expansions?  The problem with
these RAM disk utilities is that not many applications can use the file
system efficiently, and those that do usually come with custom transfer
routines that bypass the operating system.

Another possibility is to use a custom operating system that allow easy
integration of memory expansion drivers.  LUnix could be a good choice.
The drawback of this approach is that there are not many application
programs for these systems.

> On a different subject, I have not seen a directory program that allows
> over a thousand directorys to be printed.  Having loaded CMD disks with
> song programs, it is easy to run the number quite high.  Even if the
> progam dir.s were not loaded onto memory but read and pushed to the
> printer or a dir file, it would be a help.

If you are not allergic against non-Commodore computers, you could
transfer the disk directory to a bigger system and print it there.  It
should be possible with prlink.


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