M100/T102 Hardware scrolling patch

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Updated March 2022

The Model 100 and Tandy 102 (as well as KC-85, NEC and M10 machines) all have top and bottom LCD drivers that are capable of hardware scrolling. However the main ROM does not take advantage of that; it manually writes new screen data to every pixel to accomplish a scroll.

A patch has been developed now that provides an implementation of hardware scrolling. It is not a major rewrite of the LCD routines, but it modifies how the existing routines work to speed up scrolling using the hardware scroll function.

The overall patch consists of a first patch that creates about 150 free bytes in the main ROM, and then the hardware scrolling patch is implemented on top of that. 

  Note.  The so-called "base patch" is also used to enable NSC800 support.

A document that describes the patch is here. The Tandy 102 main ROM with the 2 patches applied, is here.

Version Note File
Version 2, March 2022 patch source, incl. TS-DOS bug-fix - March 2022 M102_hs.ZIP
Version 2, March 2022 Word document that describes the patch in detail hs_patch_doc.ZIP
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