Should "lagless MAME" (aka Shmupmame) be allowed?
Posted: Fri Nov 26, 2010 12:13 am
The question has come up on "The official awesome replay thread" about whether use of "lagless MAME" (aka Shmupmame) should be allowed for MARP submissions. Here's the thread: viewtopic.php?f=2&t=11642&p=52474#p52474
The recording in question is: http://replay.marpirc.net//inp/e/3/c/pr ... _win99.zip
More information about Shmupmame can be found here: http://shmups.system11.org/viewtopic.php?f=1&t=30659
MARP rule 3b states, "Since April 15, 2007, use of WolfMAME is required if you take first place in any game", so clearly Shmupmame is not allowed for first place scores. However in general for non-first place scores, other versions of MAME are currently allowed.
The potential problem is that according to Kale, "if you use a "lagless" version you are using a version on which you remove stuff from the original HW ... original Dodonpachi Arcade version has that lag and it's called sprite buffering. Sprite tables written to the work RAM are then copied thru a DMA, that DMA isn't instant, it usually takes a latency of 20 to 40 ms."
If Kale's explanation is correct, than I don't think Shmupmame should be allowed for MARP submissions.
First, it means that Shmupmame is "fixing a problem" that is actually being correctly emulated in MAME and is intentionally "breaking" the emulation and making it not behave like the arcade game. The rationale for doing this is summarized by Sikraiken as "OS overhead (and peripheral latency) add lag. With sprite/layer buffering removed, the lag is more accurate to what the actual PCB has since the actual PCB doesn't have to worry about OS overhead and peripheral latency." I understand the desire by players to try and make play "feel" as much like the arcade as possible, but IMO breaking MAME's correct emulation of the sprite/layer buffering is not the correct approach, at least for MARP.
Second, it means that Shmupmame users are at an advantage to players using any other version of MAME since they have less lag than anybody playing in any "normal" version of MAME or WolfMAME. I don't think that is fair, even for non-first place submissions.
There's been some discussion on this on "The official awesome replay thread", but I'm hoping we can move that discussion here.
-George
The recording in question is: http://replay.marpirc.net//inp/e/3/c/pr ... _win99.zip
More information about Shmupmame can be found here: http://shmups.system11.org/viewtopic.php?f=1&t=30659
MARP rule 3b states, "Since April 15, 2007, use of WolfMAME is required if you take first place in any game", so clearly Shmupmame is not allowed for first place scores. However in general for non-first place scores, other versions of MAME are currently allowed.
The potential problem is that according to Kale, "if you use a "lagless" version you are using a version on which you remove stuff from the original HW ... original Dodonpachi Arcade version has that lag and it's called sprite buffering. Sprite tables written to the work RAM are then copied thru a DMA, that DMA isn't instant, it usually takes a latency of 20 to 40 ms."
If Kale's explanation is correct, than I don't think Shmupmame should be allowed for MARP submissions.
First, it means that Shmupmame is "fixing a problem" that is actually being correctly emulated in MAME and is intentionally "breaking" the emulation and making it not behave like the arcade game. The rationale for doing this is summarized by Sikraiken as "OS overhead (and peripheral latency) add lag. With sprite/layer buffering removed, the lag is more accurate to what the actual PCB has since the actual PCB doesn't have to worry about OS overhead and peripheral latency." I understand the desire by players to try and make play "feel" as much like the arcade as possible, but IMO breaking MAME's correct emulation of the sprite/layer buffering is not the correct approach, at least for MARP.
Second, it means that Shmupmame users are at an advantage to players using any other version of MAME since they have less lag than anybody playing in any "normal" version of MAME or WolfMAME. I don't think that is fair, even for non-first place submissions.
There's been some discussion on this on "The official awesome replay thread", but I'm hoping we can move that discussion here.
-George