Talk:UNROM 512

iNES number

What is the iNES number for this? Do you need submapper numbers for one-screen mirroring mode and flashing configuration? What are the jumpers for configuring CHR RAM? --Zzo38 (talk) 06:30, 1 April 2014 (MDT)

Was planning on having this as iNES number 30. The flashing configuration is enabled by the iNES battery flag, and the one-screen mirroring is done by setting the four-screen mirroring flag. If the rom is using NES 2.0, then the non-battery backed CHR RAM field is used to specify how much CHR Ram is enabled.

As for the jumpers that configure the CHR Ram, there is 4 of them on the board. Two of them tie the respective CHR-RAM address lines to Vcc, and the other two tie the respective CHR Ram lines to the 377 outputs. Basically, for 8KB, both CHR-RAM lines are tied to Vcc, for 16KB, only one of them is tied to Vcc, and for 32KB, none of them are tied to Vcc. Caitsith2 (talk) 08:50, 1 April 2014 (MDT)

I have formed a [patch] for FCEUX that both puts the mapper as 30, and implements NES 2.0. Caitsith2 (talk) 09:01, 1 April 2014 (MDT)

OK, now it makes sense; no submapper numbers are needed. The jumpers would then be to make the board act as if there is less CHR RAM than there actually is (I suppose, it is in case you have a ROM image that specifies only 8K (or 16K) CHR RAM, and you will want to use it with the existing board). I further suppose, then, I would guess that you would set the PRG RAM sizes in the NES 2.0 header (at least one of which is zero) to put into $6000-$7FFF, which would seem to be the default specification of such a thing (although FCEUX and some others may not necessarily implement it), if not otherwise specified; since battery bit means something else with this mapper, these PRG battery/non-battery RAM would be separate from flashed ROM (although, probably you should not install battery RAM anyways, in case something is mixed up due to that). --Zzo38 (talk) 17:17, 1 April 2014 (MDT)

No wram is installed. Both of the NES 2.0 wram header fields are 0 on this board. Also, there is no means to battery back the CHR ram, so its battery field is set to 0. The only thing specified is the non-battery CHR ram size. It should be technically possible to make a board that uses wram. Just to highlight, the xmas 2013 board will play nicely with this mapper as well, as there is another 377 wired on the $8000-BFFF bank, to control the LEDs, with no conflicting effects on that boards self flashability. Caitsith2 (talk) 17:41, 1 April 2014 (MDT)

"one-screen mirroring is done by setting the four-screen mirroring flag." That seems perverse. Can we make hardwired 1scr a NES2.0 setting? Like, (4scr&vert) = (1scr)? Myask (talk) 00:15, 23 August 2016 (MDT)

Suggest responding elsewhere to keep this conversation in one place, specifically here: Talk:NES_2.0#Mirroring bits and one-screen mirroring - Rainwarrior (talk) 11:51, 23 August 2016 (MDT)

Name confusion?

I know the RetroUSB board says "UNROM 512" on it, but I feel there's confusion between this and just UxROM with 512k (which is a subset of features, maybe?). Maybe "Sealie UNROM 512" instead? Maybe it doesn't matter and we should just embrace the confusion. :P (Also funny to me: the Sealie UNROM 512 boards I have incorrectly say "ReproPak MMC3" on the back.) - Rainwarrior (talk) 13:16, 22 August 2016 (MDT)

I agree. For me "UNROM-512" would be mapper #2 with either 512 kbits (64 kiB, 4 banks) or with 512 kiB (32 banks), but probably the former since the number usually refers kilobits, as in NROM-128 and NROM-256. I know the confusion between UNROM and mapper #2, which are two different things, comes from very early days of NESDEV and has been going on since. (i.e. Crazy climber is not mapper #2 but is UNROM, Maniac Mansion (J) is mapper #2 and not UNROM). But this name adds yet another unnecessary confusion on an already confusing name. Bregalad (talk) 13:40, 22 August 2016 (MDT)