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| author | Thomas Voss <mail@thomasvoss.com> | 2024-02-13 13:02:28 +0100 |
|---|---|---|
| committer | Thomas Voss <mail@thomasvoss.com> | 2024-02-13 13:11:47 +0100 |
| commit | 79e6af86ca526d5fb56af6f6ca3da713e3a5e9f9 (patch) | |
| tree | 752f1c26d1f122dcf58374ac78db109c9578be45 /src/NOTES | |
Genesis commit
Diffstat (limited to 'src/NOTES')
| -rw-r--r-- | src/NOTES | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/src/NOTES b/src/NOTES new file mode 100644 index 0000000..d155ab1 --- /dev/null +++ b/src/NOTES @@ -0,0 +1,7 @@ +The shl and shr instructions are often documented to take both a Vx and a +Vy argument. It’s a bit unclear what the behaviour here is meant to be. +The original CHIP-8 implementation shifted Vy by 1 and stored the result +in Vx. Some GitHub projects shift the value in Vx by the value in Vy. +Ahoy takes the approach of SCHIP where Vx is shifted by 1 and Vy is +ignored. The Ahoy assembler does not recognize a second Vy argument to +either instruction. |