Well, I've ordered the PCB's for both the devkit and the cartridge, and most of the parts are on their way (except for the WRAM and a 5 pin inverter that adding the WRAM required...), so I'll know in a week or two whether it'll work or if I have a bunch of expensive, bogus PCB's
I just want to say that Memblers is right, Myro PCB are inexpensive and easy to work with, hopefully the quality will also match.
Theoretical capabilities:
512 KB PRG FLASH
8 or 32 KB WRAM (not battery backed, but pinned out for TI NVSRAM as well as straight SRAM, although the TI parts may be too tall to fit in an unmodified case)
128 KB CHR RAM
Spot for CIC with jumper for both normal and B1 revisions (probably pointless, but hey, I'm a perfectionist).
Correct NES board sizing: 0.047 inch thick, 2.5 mm pin spacing.
Note: I still need someone to look in a few PAL carts to make sure the CICs are wired up the same (see the CIC pinout thread), as I won't have access to my PAL carts for another month or so.
Native mode:
16 / 32 KB PRG switching (16 KB mode has one page locked)
4 / 8 KB CHR switching of full 128 KB VRAM (tepples should like this ^_^)
Mirroring control (one screen or H/V, but no four-screen)
Flash ROM write control, so cartridge can (and will, since I'm not building an external programmer) be self-writable via NES code
(The write control is actually the entire reason the mapper started getting complicated, as I was originally going to do a UNROM flash cartridge, but I needed extra logic to disable the mapper and allow flash writes, and switchable mirroring would be nice, and why stick a PAL on there when a CPLD isn't much more, and makes life easier, and so forth...)
In addition to a native mode, it also supports most every type of discrete logic mapper, and all MMC1 board types except SUROM (the last 64 KB will be locked with backup firmware to load over the comms cable, so you can't fit a full 512 KB on there) and SOROM (I haven't written the code for this yet, but it should fit. I don't have any SOROM games so it's a lower priority)
Discretes that I'm sure will work:
AMROM
ANROM
AOROM
BNROM
CNROM
GNROM
MHROM
NROM
RROM
UNROM
UOROM
Color Dreams / Wisdom Tree (everything but AGCI 50282)
Doable right now, but may be cut if I need the space for something else:
NINA-03 / 06
Tengen 80008
Should be doable, i.e. unimplemented
Camerica BF9093 / BF9097 (don't have the games, but the mapper seems sane)
CPROM / Videomation (have it, but honestly, it's not worth the effort for a mediocre paint program)
Might be doable. I don't have any of these games, but the mapper docs indicate they'll fit into my design.
Mapper 70: Bandai 74161/32
Mapper 78: Irem 74161/32
Mapper 87: Jaleco 74138/74
Mapper 93: Mapper 93
Mapper 140: Bio Senshi Dan
Mapper 145: Sachen SA-72007
Mapper 149: Sachen SA-0036
Kinda doable:
NSFs that either don't bankswitch, or bankswitch once (i.e. expect the loader to use the bankswitch values, but never write to the $5FFx registers).
Devkit Capabilities:
128 KB Flash
8 or 32 KB RAM
A few extra I/O pins (going to wire up a RGB LED for the power light I think, to indicate comms status or for debugging, or whatever)
Works in a similar fashion to CopyNES, with the device between the CPU and the NES board, although it uses different parts and has (will have) different firmware, and it may or may not fit I measured pretty closely, but it's a tight fit between it and the end of the case (no cable is used, it plugs directly into the NES board)
32 KB version can act as a RAM cartridge if you stick in a VRAM game with the appropriate mirroring (8 KB can run code too, but 8 KB isn't a ton of space to work with).
I just want to say that Memblers is right, Myro PCB are inexpensive and easy to work with, hopefully the quality will also match.
Theoretical capabilities:
512 KB PRG FLASH
8 or 32 KB WRAM (not battery backed, but pinned out for TI NVSRAM as well as straight SRAM, although the TI parts may be too tall to fit in an unmodified case)
128 KB CHR RAM
Spot for CIC with jumper for both normal and B1 revisions (probably pointless, but hey, I'm a perfectionist).
Correct NES board sizing: 0.047 inch thick, 2.5 mm pin spacing.
Note: I still need someone to look in a few PAL carts to make sure the CICs are wired up the same (see the CIC pinout thread), as I won't have access to my PAL carts for another month or so.
Native mode:
16 / 32 KB PRG switching (16 KB mode has one page locked)
4 / 8 KB CHR switching of full 128 KB VRAM (tepples should like this ^_^)
Mirroring control (one screen or H/V, but no four-screen)
Flash ROM write control, so cartridge can (and will, since I'm not building an external programmer) be self-writable via NES code
(The write control is actually the entire reason the mapper started getting complicated, as I was originally going to do a UNROM flash cartridge, but I needed extra logic to disable the mapper and allow flash writes, and switchable mirroring would be nice, and why stick a PAL on there when a CPLD isn't much more, and makes life easier, and so forth...)
In addition to a native mode, it also supports most every type of discrete logic mapper, and all MMC1 board types except SUROM (the last 64 KB will be locked with backup firmware to load over the comms cable, so you can't fit a full 512 KB on there) and SOROM (I haven't written the code for this yet, but it should fit. I don't have any SOROM games so it's a lower priority)
Discretes that I'm sure will work:
AMROM
ANROM
AOROM
BNROM
CNROM
GNROM
MHROM
NROM
RROM
UNROM
UOROM
Color Dreams / Wisdom Tree (everything but AGCI 50282)
Doable right now, but may be cut if I need the space for something else:
NINA-03 / 06
Tengen 80008
Should be doable, i.e. unimplemented
Camerica BF9093 / BF9097 (don't have the games, but the mapper seems sane)
CPROM / Videomation (have it, but honestly, it's not worth the effort for a mediocre paint program)
Might be doable. I don't have any of these games, but the mapper docs indicate they'll fit into my design.
Mapper 70: Bandai 74161/32
Mapper 78: Irem 74161/32
Mapper 87: Jaleco 74138/74
Mapper 93: Mapper 93
Mapper 140: Bio Senshi Dan
Mapper 145: Sachen SA-72007
Mapper 149: Sachen SA-0036
Kinda doable:
NSFs that either don't bankswitch, or bankswitch once (i.e. expect the loader to use the bankswitch values, but never write to the $5FFx registers).
Devkit Capabilities:
128 KB Flash
8 or 32 KB RAM
A few extra I/O pins (going to wire up a RGB LED for the power light I think, to indicate comms status or for debugging, or whatever)
Works in a similar fashion to CopyNES, with the device between the CPU and the NES board, although it uses different parts and has (will have) different firmware, and it may or may not fit I measured pretty closely, but it's a tight fit between it and the end of the case (no cable is used, it plugs directly into the NES board)
32 KB version can act as a RAM cartridge if you stick in a VRAM game with the appropriate mirroring (8 KB can run code too, but 8 KB isn't a ton of space to work with).