Mega Man 2: Mega Man 2 + Rockman 2 Sprite Lag Reduction Patch is a fan-made modification for the Nintendo Entertainment System version of Mega Man 2 and Rockman 2. It addresses inefficiencies in the sprite buffer clearing method, reducing CPU usage and lag by approximately 8%. The patch is available in two versions: mm2spritelag.ips for Mega Man 2 and rm2spritelag.ips for Rockman 2.
This patch eliminates a gross inefficiency in MM2/RM2's sprite buffer clearing method, reducing overall CPU usage by about 8% and lag by at least as much.
This patch has both Mega Man 2 and Rockman 2 versions: mm2spritelag.ips and rm2spritelag.ips, respectively.
For the people asking if this is related to Puresabe's sprite lag reduction hack: not as far as the author knows. The author looked at his hack a little bit after the first person asked. The author doesn't think they use the same method, but they can't say for certain without taking more time and understanding his hack better.
Mega Man 2 Sprite Lag Reduction Patch
v1.0
By Justin Olbrantz (Quantam)
This patch eliminates a gross inefficiency in MM2/RM2's sprite buffer clearing method, reducing overall CPU usage by about 8% and lag by at least as much.
This patch has both Mega Man 2 and Rockman 2 versions: mm2spritelag.ips and rm2spritelag.ips, respectively.
Others with the same PRG-ROM checksums will likely work just as well.
COMPATIBILITY
The clear OAM buffer function uses memory address $c7 as an out-of-interrupt temporary. It should be safe to use this address for other out-of-interrupt temporaries so long as they don't overlap with the clear OAM buffer function.
This patch uses the ROM range (file offsets) 2bb46-2bb87 that was previously free.
INCORPORATION INTO OTHER HACKS
As everybody needs less lag, it's perfectly fine to incorporate this patch into other hacks (especially content hacks). In such cases, please include a line in the readme (or hack description/credits if there is no readme) indicating that the derivative hack uses this and link to this patch on RHDN.
Finally, thanks to Kasumi for pointing out this inefficiency in MM2 on the NesDev Discord.
Mega Man 2: Mega Man 2 + Rockman 2 Sprite Lag Reduction Patch Game Wiki
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