M100/T102 Hardware scrolling patch

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 binary, 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

TIPS

  Hardware scroll works when the LABEL line is DISABLED. 
  This is important in TELCOM.  
  Turn off LABEL line to see the benefit of hardware scrolling.

  Same tip for other situations where LABEL line is on.
  Like in BASIC or TEXT.  
  Again, turn off for fast scrolling.