So in the case of LDA (addr),y the last access before the open bus access is the one where it reads the hibyte of the address from zeropage. The value will be (under typical conditions) whatever value was on the data bus before the open bus access. My patch should have done things differently, though I guess it's only a moot point. I didn't realize the open bus behaviour should return the high address byte. Rainwarrior wrote:Hm Low G Man's reads seem to be in a range around ~$7C80, though the value is then given a CMP #$30, so I guess it's tolerant to a wide range of "high" values. (Another option would be to disable WRAM for NROM/AxROM and other mappers which are not "supposed to" have it, but I kind of like having the WRAM there for homebrew development.) This gives me another reason to initialize WRAM to a known state when loading games that don't have the "battery backed SRAM" bit set in the iNES header. It may have worked on the official RetroUSB mappers if they don't map the WRAM at all in AxROM, although the open bus behavior on PowerPak still would not match the original cart, so it working would have been a lucky coincidence. PowerMappers, IIRC, will map WRAM to $6000.7FFF regardless of the mapper, so that's why loading an empty. It's a matter of the game reading $6000.7FFF despite not having WRAM (exactly same issue as in Low G Man). The NES 2.0 support in PowerMappers is quite limited (the main use case was to configure the CHR RAM size).īTW, it's not a bus conflict issue. Koitsu wrote:Supposedly thefox's PowerPak PowerMappers v23 releases (and/or later) provide NES 2.0 header support, so basically a modified version of the ROM that sets up the NES 2.0 headers properly for this + use of PowerMappers v23 or later is probably the "cleanest" way to solve it.
0 kommentar(er)
