byuu says:
Changelog:
- emulator/random: new array function with more realistic RAM
initializations
- emulator/random: both low and high entropy register initializations
now use PCG
- gba/player: rumble will time out and disable after being left on for
500ms; fixes Pokemon Pinball issue
- ruby/input/udev: fixed rumble effects [ma\_rysia]
- sfc/system: default to low-entropy randomization of memory
The low-entropy memory randomization is modeled after one of my SHVC
2/1/3 systems. It generates striped patterns in memory, using random
inputs (biased to 0x00/0xff), and has a random chance of corrupting 1-2
bits of random values in the pool of memory (to prevent easy emulator
detection and to match observed results on hardware.)
The reasoning for using PCG on register initializations, is that I don't
believe they're going to have repeating patterns like RAM does anyway.
And register initializations are way more vital.
I want to have the new low-entropy RAM mode tested, so at least for the
next few WIPs, I've set the SNES randomization over to low-entropy.
We'll have to have a long discussion and decide whether we want official
releases to use high-entropy or low-entropy.
Also, I figured out the cause of the Prince of Persia distortion ... I
had the volume under the audio settings tab set to 200%. I didn't
realize there were SNES games that clipped so easily, given how
incredibly weak SNES audio is compared to every other sound source on my
PC. So with no entropy or low-entropy, indeed the game now sounds just
fine.
I can't actually test the udev fixes, so I guess we'll see how that goes
for Screwtape and ma\_rysia.
byuu says:
Changelog:
- higan/emulator: added new Random class with three entropy settings:
none, low, and high
- md/vdp: corrected Vcounter readout in interlace mode [MoD]
- sfc: updated core to use the new Random class; defaults to high
entropy
No entropy essentially returns 0, unless the random.bias(n) function is
called, in which case, it returns n. In this case, n is meant to be the
"logical/ideal" default value that maximizes compatibility with games.
Low entropy is a very simple entropy modeled after RAM initialization
striping patterns (eg 32 0x00s, followed by 32 0xFFs, repeating
throughout.) It doesn't "glitch" like real hardware does on rare
occasions (parts of the pattern being broken from time to time.) It also
only really returns 0 or ~0. So the entropy is indeed extremely low, and
not very useful at all for detecting bugs. Over time, we can try to
improve this, of course.
High entropy is PCG. This replaces the older, lower-entropy and more
predictable, LFSR. PCG should be more than enough for emulator
randomness, while still being quite fast.
Unfortunately, the bad news ... both no entropy and low entropy fix the
Konami logo popping sound in Prince of Persia, but all three entropy
settings still cause the distortion in-game, especially evident at the
title screen. So ... this may be a more serious bug than first
suspected.
Tim Allen