LoROM vs HiROM

To summarize:

LoROM (mode $20): A15 and A23 skipped
This fills the second half of each bank and starts at the "low" part of cartridge address space: banks $00/$80 on up.

HiROM (mode $21): A22 and A23 skipped
This fills the whole bank, starting at $40/$C0.

ExHiROM (mode $25): A22 skipped, A23 inverted
Similar to HiROM, filling banks $C0-$FF then $40-$5F (in practice) or $40-$7D (in theory).

ExLoROM (unofficial)
Mentioned in some places, but not used in licensed games nor with an agreed upon definition to my knowledge.

The official Super NES programming manual reportedly names these modes by the value at $00FFD5 in the internal header ($20, $21, or $25). I guess some people just prefer names as more memorable, just as people in the NES scene prefer "AOROM" and "UNROM" to "mapper 7" and "mapper 2".

Unlike with NES mappers named after their exemplar cartridge boards, these names don't appear on cartridge boards. But I can see where some of these names come from, especially before 32 Mbit fast ROMs became common. A 16 Mbit LoROM covers $808000-$BFFFFF with holes for the system area mirrors, and in the slow ROM era, the mirror at $008000-$3FFFFF was just as likely to be used. A 16 Mbit HiROM covers $C00000-$DFFFFF, which is a higher address range.

Now my question: Who coined the names LoROM, HiROM, and ExHiROM? Copier makers?

You can do that with HiROM too. The upper half of each bank also gets mapped into the LoROM area.

It was me. And a buddy of mine named Frank.

"It was me, koitsu!"

Also, five year old topic bump >_>

Jojo <3

Wait? Tepples bumped the thread?

First I searched to see if there was already an answer. Not finding one, I asked in the closest topic that fit. I guess my preference for a necro over a dupe is informed by the classic Flash slideshow "Posting and You" (SWF | YouTube).

Have you ever felt weird seeing this many people (that being most of SNESdev) using a term you created? I'd feel like some sort of celebrity.

> I guess my preference for a necro over a dupe is informed by the classic Flash slideshow "Posting and You"

Really, my only problem with old topic bumps is it not being clear that it happened. I read the first post and was getting ready to start my usual "chain of replies to messages in the thread" until I saw I had already replied, and then realized it was from 2012.

If I had all the time in the world to design a dream forum, then the way I'd do it would be that topics pseudo-locked after X days/months of no activity. You could still post a reply. But it would create a new topic with a special "link" icon, and there would be a special link at the top of the thread to the old discussion.

Of course, we can't do that with phpBB3. As such, you're the admin here, so it's your rules :)

> Have you ever felt weird seeing this many people (that being most of SNESdev) using a term you created? I'd feel like some sort of celebrity.

He's also the person that discovered and documented Felon's banana register ;)

Joking aside, he was a large part of the early efforts of documenting the SNES. Even though that information isn't really useful today, now that we know so much more and have far better documentation (thanks to anomie), we're all very aware and gracious of the fact that we can see further thanks to standing on the shoulders of giants that came before us. So he'll always be immortalized as an early pioneer of the SNES scene.

That said, LoROM/HiROM is one such thing that's really not relevant anymore. This is the reality of SNES mapping:

https://preservation.byuu.org/Boards

There aren't two (or three with ExHiROM) board layouts: there are around ~110 PCB layouts, of which sort into ~60 memory map models (I don't have them all in my DB yet), of which there are ~30 or so unique layouts that ROM data can exist within. And that's just for commercial carts. The sky's the limit with unofficial designs.

Breaking down LoROM/HiROM is basically the decision whether or not to wire up A15 to the ROM chips / memory mapper or not. It's fine to generalize with these terms, but if we want to be more precise and improve the quality of emulation, we need to move past simplifications like this.

I was completely joking -- I didn't create them. I just wanted to say something that would definitively answer Tepples' question without giving him an avenue for weirdness. ;-) At least it got byuu to make a Jojo reference, which really did get me laughing (I haven't enjoyed an anime/manga that much since Jungle wa itsumo Hare nochi Guu).

The LoROM/HiROM terms were already in use by the time I started getting into SNES development back in 1992 (or was it 1993?). I have several different ideas as to where/how they originated, but I'd rather keep those to myself -- the less misinformation spread, the better. (I had never heard of "ExHiROM" until sometime in maybe 2008?). But if I had to go out on a limb publicly, I would say it probably came from the Amiga/SNES/warez crowd who were distributing ROM sets back in the day. Pretty much all the .nfo files had those labels. "Lo" is probably just a convenient/short (fewer characters) way to say "less" and "Hi" meaning "more". I mention the Amiga because that's a system where you've got 9 billion different kinds of RAM (ChipRAM, SlowRAM, FastRAM, MB RAM, AccelRAM), even though I'm pretty sure all of those have no actual relation to the SNES, I just think the "naming convention" syntax/style might have carried over. There weren't 24mbit or 32mbit carts at the time those terms were created -- I know this for a fact because a paper copy of the official docs I have don't even mention mode 25, nor do they have any of the PCB layouts + memory map details that the last-known-version has.

My memory fails me here... Anyone remember what terminology the Wildcards, Magicoms, Fighters and assorted Doctors used?

So next time you're telling jokes, could you please make it explicit ? Here it really looks like you were serious about inventing those terms, and this would have been credible.

Not that I personally care who invented them, but I just like it to be clear when people aren't serious.

That's is indeed ironic. I believed it, as would anyone not familiar with the SNES scene reading that post. I don't personally care either, considering I still don't really understand what all those terms mean, but still.

I think they should have different names.

For example, half bank ROM vs full bank ROM.

Yeah, hate to admit it, but I thought you were serious too, hahah.

I do know it's scene related, as Nintendo used mode numbers (20, 21, 25, ...)

I wasn't around until late '97, early '98 when emulation was starting to become part-way usable (if you didn't mind using something one year less developed than this, at least ... sadly no videos on ESNES v0.11b, or Snes9Xw v0.2.0); so I don't really know where the terms came from either.

(Fun anecdote: I basically begged daily for a computer from as young as I can remember. Didn't ever get an actually usable one until late '97, and so I missed out on the golden age of BBSes, the early internet, and the early emulation scene.)



They were using it to refer to Tales of Phantasia around the ZSNES forums in 2004. I suspect they coined it upon emulating said game, which would've been back around '99 or so?

This is bad that I don't even remember, but ... ExLoROM might've been me? I think it was an idea to expand LoROM games to support > 32mbit, and I believe DMM used it in his translation of Dragon Quest 3R? I know FuSoYa added this support to his Lunar Magic tool, and also released new versions of emulators to support it, so they could expand Super Mario World beyond the 32mbit limit.



I know their file extensions, at least.

mgd => Multi Game Doctor
mgh => Multi Game Hunter
sf2 => Professor SF2 (English/US/UK? version of Game Doctor)
gd3 => Game Doctor 3
gd7 => Game Doctor 7
fig => Pro Fighter
smc => Super Magicom (actually very uncommon device, yet common extension)
swc => Super Wildcard
ufo => Super UFO

Pretty sure all of them had variations on copier header format (but a consistent size), and also had different rules around interleaving games or not. My Super UFO definitely interleaved 'HiROM' games, as it were.

However, later copiers could often boot games from several other copier header formats.

The Super UFO 8.3j didn't have any actual terminology around 'LoROM/HiROM' anywhere in the UI. It was all hidden in the background technical details.



For people who don't follow the idea of omitting address lines, you could say 64k granularity vs 32K granularity.

I for one enjoyed koitsu's good clean joke. (:

Anyway, I looked around for some old file_id.diz:s and "HI-ROM" was around at least as early as 1992. "SlowROM" fixes, too.

Exhibit A:

Exhibit B:

I couldn't find any reference to "LO-ROM" though, so that might've been coined by the early emulation scene by simply making up an antonym to "HI-ROM".

Yeah Koitsu can't be explicit that he is joking if he is trying to fool you can he? Or else it wouldn't work.

From my own notes there are five main map modes, following the official naming in the header:
Mode 20 - LoROM
Mode 21 - HiROM
Mode 22 (S-DD1) (says "reserved for future use" in a revision of the official dev docs) - ExLoROM
Mode 23 (SA-1) - Doesn't seem to have a "scene name"?
Mode 25 - ExHiROM

The byte in the header:
001A0BCD (basic value $20)
A = 0 means SlowROM (+ $0), A = 1 means FastROM (+ $10).
B = 1 means ExHiROM (+ $4)
C = 1 means ExLoROM (+ $2)
D = 0 means LoROM (+ $0), D = 1 means HiROM (+ $1), is used with B and C in case of extended ROMs.

Mode 23 fills the requirements of both ExLoROM and HiROM?
This puzzles me as SA-1 games aren't exactly few, it would seem it would have a scene name.

The scene name is SA-1. As on the NES, the rule is that a mapper dominated by a big ASIC gets named after that ASIC, while a board with no big ASIC is named in some other memorable way. For NES, said memorable way is the silkscreened name, while for Super NES, it's the fact that $80-$BF precedes $C0-$DF, just expressed in a manner that looks like an NES board name (or like the parts of Amiga memory).

As far as ROM mapping is concerned SDD1 and SA1 are extremely similar. The only difference is that with the SA1 both the "LoROM" and "HiROM" regions can be freely bankswitched in 1 megabyte chunks, whereas with the SDD1 only the "HiROM" region can be bankswitched, the "LoROM" region being fixed to the first 2MB of ROM.

"The scene" confusingly uses ExLoROM to refer to two completely different things. One is the SDD1; the other is a mapping apparently invented by the ROM hacking scene (no commercial cartridges ever used it, nor is it attested in any documentation) that's analogous to Mode 20 in the same way Mode 25 is analogous to Mode 21: one 32 MBit ROM mapped in the fast banks in Mode 20 fashion, and another up-to-32 Mbit ROM mapped in the slow banks. A ROM image using this invented mapping would have its Nintendo header and vectors at 0x407Fxx.

I see, so if it would have an official name I guess it would be Mode 24.

In that case it's best to use "ExLoROM" only for this Mode 24 and "S-DD1" for Mode 22 to stay consistent.

In other words:
Official Name - Scene Name
Mode 20 - LoROM
Mode 21 - HiROM
Mode 22 - S-DD1
Mode 23 - SA-1
Mode 24 - ExLoROM (unofficial map mode)
Mode 25 - ExHiROM

Much better.


I guess S-DD1 is called ExLoROM only because it's the closest thing to it among the official map modes, although it's not 100% analogous.