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D&D General The Interoperability of OD&D, Basic, AD&D, and (kinda) 5e

Snarf Zagyg

Notorious Liquefactionist
Another thread had me pondering a notion that I usually take for granted; the compatibility (I will use that term, but more precisely I thinking about interoperability) of the older TSR D&D Systems.

One thing that might be helpful for people is some quick definitions of the various acronyms that I, and others, use:


Many older gamers, such as myself, think of compatibility of older TSR systems in terms of the ability to go from a D&D System to a non-D&D System; famously, the 1e DMG had rules for converting characters between Gamma World, Boot Hill, and D&D. This was due to the concept espoused by Gygax (and followed by some) that characters would be able to engage in various adventures in the multiverse- in different primes.

Underlying this was a concept that I had never thought about, because it was so basic and assumed when I was playing that it was not even discussed. Specifically, the various "branches" of D&D are all compatible. More specifically-
OD&D, Moldvay, B/X, BECMI, 1e, and 2e are all fundamentally compatible (interoperable).

At a very basic level, the entire line of D&D products from TSR is the same game. I don't mean that some details aren't different. And they can be major; obviously, the Moldvay Basic split (race as class, otherwise referred to as "Basic") has some key differences. And the gradual accretion of rules over time made the play experience of late 2e wildly different from that of 1975 OD&D.

...and yet, all of these games are fundamentally the same. They are all interoperable. Perhaps the best, and easiest, example of this is B2 (Keep on the Borderlands). B2 was originally written for OD&D (Holmes). But the module shipped with Basic (Moldvay). The module was so ubiquitous, that it was commonly run as an introductory adventure for 1e characters; and became so entrenched as a "popular trope" that it continued to be run well into the 2e era.

All of this is to say that while there are numerous small differences over time, the entire structure of all of the D&D systems from 1974 through 2000 is so similar, so based on a common core, that the materials made for them are easily used without any adaptation.

This doesn't mean that things did not change; obviously, a 1e UA character (or a 2e Kit character) would be much more powerful than an OD&D character. But because these systems didn't use "CR" or other balancing material, this wasn't really seen as a problem (just add or subtract an ogre).

That is why 3e is the first "big break" in that lineage. 3e, at a very basic level, is not fundamentally compatible with the systems that came before; it does require extensive conversion and adaptation. As does 4e.

Which comes around to 5e. One of the strengths of 5e is the way in which it both takes some of the mechanical and play improvements of 3e and 4e while still hearkening back to the TSR lineage of the game. It is possible to run B/X and 1e modules in 5e "on the fly" if you're comfortable with an assumed save/ability conversion, or with a minimum of prep work.

What do you think?

1. Do you think that the old TSR D&D games are largely compatible?

2. What is your experience, if any, converting TSR material to 5e? 3e material? 4e material?
 

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I run TSR era BECMI modules for a 5e campaign on the fly all the time, and back when I ran BECMI, used any TSR-era module regardless of edition on the fly. Never even really thought about it back then, and it's minimal effort to do so now with 5e. I never ran 3e, and didn't play 4e long enough to not use 4e only material.
 

Hussar

Legend
Well, we've had this conversation, so, you know my answer. :D

No, I do not think that TSR D&D games are largely compatible. At least, not to the degree where you could simply open up Keep on the Borderlands and play it using a group generated using 2e rules. The power disparity is simply too great. Things that may have been a challenge to a 1e group become laughably easy to a 2e group because of the much greater range of spells, powers, and power level (even ignoring things like Skills and Powers which I never used).

I think the simplest example would be to compare the damage output of a bog standard party - 3 fighters, a cleric, a wizard and a thief between the editions. From OD&D through Basic, then to AD&D and then 2e, that party's damage output isn't even close. Step up to about 7th level? That 2e party is easily four or five levels ahead of the Basic/Expert party and is capable of things that the B/E party could never do.

-------------

Funny you should ask that. I'm currently using the Chaos Scar modules from 4e Dungeon in my new 5e campaign. So, I'm converting a boatload of fairly short adventures. It's tricky, mostly because 5e is so sparse with its monsters. I mean, heck, 5e doesn't even have giant ants. :D I've definitely turned to some 3rd party publishers to fill in the gaps.

It's honestly too early to tell how well it translates across. We're only 3 session in. I'll have a better feel for things after a couple more sessions.
 

There was a lot of similarities between the earlier editions, but mechanically they were different enough to prevent use of characters between editions (although converting them wasn't impossible). The original concept for 2E was supposed to allow 1E characters to play in 2E, but that didn't make it to the final version.

Two aspects that were easily transferable was magic items and adventures. Magic items and adventures could be used almost interchangeably between those editions. A few tweaks here and there were all you really needed to fit the edition you were playing. It was quite common to use BECMI adventures in AD&D, since not only were there far more of them, but they were usually much better than the AD&D ones.

Those adventures could be used in any edition, but converting them to 3E or 4E was harder than the earlier editions or 5E. Monsters and magic items had difficulty in those editions, because converting them (if they didn't make the edition) took a lot of work to make them balanced. 4E had extra difficulty because of the encounter design assumptions. Conversely, converting 3E adventures back to earlier editions or 5E has been fairly simple. I haven't converted any 4E adventures to any other edition, but to be honest I didn't like any of the ones I saw.
 

Snarf Zagyg

Notorious Liquefactionist
. It was quite common to use BECMI adventures in AD&D, since not only were there far more of them, but they were usually much better than the AD&D ones.

There is quite a bit I disagree with about what you wrote, but this is something I wanted to pull out. While quality is a subjective issue, quantity isn’t.

There were far more AD&D adventures than BECMI ones.
 

Voadam

Legend
The main differences were stats and classes so the player end. The DM material like modules and monsters were easily swappable.

B/X BECMI line had a range of stat modifiers that ran up to +3 bonuses and started at lower stats, while AD&D had a reverse bell curve of bonuses where a 14 might get you nothing but had the extremes of percentile strength giving significant damage modifiers from first level on.

AD&D after Unearthed Arcana also had weapon specialization giving more attack bonuses, damage, and attacks from first level, plus AD&D had some weird optional rules on two weapon fighting. AD&D also had a cool martial arts system from Oriental Adventures.

Basic starting with the Master Set in BECMI had weapon mastery.

Attack bonuses increased more for AD&D classes over levels.

Clerics in Basic only got spells starting at second level and did not get bonus spells for wisdom. AD&D ones had them from first level and got bonus ones for wisdom which represented a significant increase in magical healing at low levels.

Basic magic missiles, fireballs, and lightning bolts were not capped for damage so that was an increase over 2e D&D.

HD increased from OD&D to Basic to AD&D. In OD&D it was d6s mixed with some levels of +1 hp, in Basic it was from d4 to d8, in AD&D it was d4 to d12, with a bunch getting a die higher than in basic so an average of +1 per level increase. More characters got bonus hp from the Basic stats, though fighters could get more bonus ones on the reverse bell curve of AD&D.

On the monster end most stats were the same across editions. Dragons and giants got a significant HD boost going from 1e to 2e though and skeletons and zombies doubled in HD from OD&D's 1/2 and 1 HD to Basic and later editions' 1 and 2 HD. Shadows are not undead in Basic but are in AD&D. Magic resistance and psionics were something added in for AD&D. Basic monsters had a morale with some suggested rules for determining if they ran away or surrendered.

Initiative was different from Basic to 1e to 2e but were easily swappable.

I used B/X modules, monsters, and magic items in AD&D games without pause. I used the Moldvay Basic explanations of a lot of rules in AD&D regularly.

I played in an AD&D game that incorporated BECMI's weapon mastery.
 

Li Shenron

Legend
1. Do you think that the old TSR D&D games are largely compatible?

2. What is your experience, if any, converting TSR material to 5e? 3e material? 4e material?

I mostly played only BECMI among old D&D editions so it's hard to tell, but I certainly don't think BECMI, 3e, 4e and 5e are compatible.

I might have a too strict definition of compatibility, but IMHO the ultimate compatibility test is to drop a character or monster as-is from one edition into another edition rules and see if everything still make sense, without changes. With this in mind, maybe even 3.5 is not fully compatible with 3.0 as some stuff uses action types which don't exist in 3.0, and because of a different skills list and a few minor things.

Converting adventures is not a big deal however. I have run TSR and 3e adventures in 5e. I convert them mostly on the fly.

For standard monsters, I just use the 5e version. This is near-zero effort. I check the CR in case is too high for the PCs in which case I might replace the monsters with others or give some favorable conditions (e.g. monsters may be asleep, distracted, wounded, unarmed, frail/subpar...). But normally I run the game with a sandboxy approach so if you sometimes encounter a very hard monster, so be it.

Unimportant NPCs are replaced with stock NPCs from the MM, with minimal variations (e.g. if the adventure mentions a particular weapon or ability).

Important NPCs I prefer to redesign using PC classes because it's faster, but I don't go full details. For example I certainly do not bother with all known spells of a spellcaster, and maybe not even all their prepared spells, just those which I think they will use. Same with feats and other abilities.

Unique monsters are potentially the worst, in theory I should use DMG rules and build them from scratch but I think it's just fine to replace with a similar creature from the MM, and add whatever special ability or two make the monster really unique. It needs to be said however that often "unique" monsters don't even have unique abilities.

Non-combat challenges are described either with thief skills % or 3e DCs. Exact conversion on either to 5e DCs is possible but I don't think it's that important, as long as you stay in the range.

Sometimes, especially old adventures refer to specific spells like "the magic doors open if a 7th-level Cleric casts Sticks to Snakes". Obvious if the spell doesn't exist in 5e, it has to be replaced.

Magic items I make up even more, but I don't necessarily conform even to 5e DMG magic items in general, I usually prefer each magic item to be whatever. This includes also the possibility that I do not convert it at all, if it doesn't have a direct rules incompatibility or breaks balance.
 

Voadam

Legend
No, I do not think that TSR D&D games are largely compatible. At least, not to the degree where you could simply open up Keep on the Borderlands and play it using a group generated using 2e rules. The power disparity is simply too great. Things that may have been a challenge to a 1e group become laughably easy to a 2e group because of the much greater range of spells, powers, and power level (even ignoring things like Skills and Powers which I never used).

I think you underestimate how vulnerable low level AD&D characters are.

I ran B1 In Search of the Unknown from B/X for 1st level 1e AD&D characters including a drow ranger with double specialized two weapon fighting short swords and 18 percentile strength plus a drow cleric magic user (dual wielding maces) in the party so tons of healing and attacks and damage compared to a B/X group of 1st level.

I do not remember it being noticeably easier or less dangerous for them than the AD&D intro dungeon moathouse from the 1e Temple of Elemental Evil I ran them through as well.
 

the Jester

Legend
1. Do you think that the old TSR D&D games are largely compatible?

Largely, but not completely. I think the biggest hang up in taking pcs from one TSR edition to another is 2e priests; I don't think I ever played in or ran a game in which "generic clerics" were the norm in 2e, instead of specialty priests. But it was simple to just use Monster Manual orcs instead of Basic orcs without needing to change anything else.

2. What is your experience, if any, converting TSR material to 5e? 3e material? 4e material?

I've run modules from every edition from 1e through 4e in 5e without doing a formal conversion of anything but monsters and maybe some key magic items or spells. Mostly, I convert on the fly. I've found it to be fairly easy; usually I just swap in a goblin for each goblin sharpshooter or goblin cutter or whatever and let it ride. This does mean that e.g. 4e minions are more of a challenge in my conversions, since they're no longer minions per se, and once in a while I need to be cautious when a monster's CR has changed significantly; but overall, it has worked fine.
 

Mark Hope

Adventurer
1. Do you think that the old TSR D&D games are largely compatible?
Yes, they are largely compatible - mainly when it comes to using adventures. Although the core mechanical chassis of the rules is largely the same, there are enough differences so that, for example, you can't really use a Basic D&D fighter alongside a 2e weapon specialist and expect them to perform the same. And there are lots of differences like that. There's a definite power curve from OD&D to late-era 2e - the latter is closer to early 3e in what characters can do, particularly when you're adding in S&P material.

However, if you're familiar enough with the material, it's easy to pick up an adventure or supplement from any TSR edition and use it with another. You may need to adjust hit points or damage output, for example, or some other edition-specific rules material (morale checks or thief skills or clerics or whatever) but it's quite possible. My 2e-hack is doing this at the moment, actually, mixing stuff from several editions all at once.

2. What is your experience, if any, converting TSR material to 5e? 3e material? 4e material?
I play in a 5e game but don't run it so I can't speak to that, and I only played a bit of 4e. I converted stuff to 3e quite a bit (primarily Dark Sun) and found that it did need quite a bit of work - particularly as 3e grew in scope, the characters are far more powerful. One thing that I have noticed, however, is that it's very easy to convert backwards from 3e/PF to AD&D, particularly the 2e hack that I'm using. I don't need to use all a monster's various powers and feats and whatnot, but I can get an attack bonus and use hit points and basic damage ratings more or less as-is (minus bonuses for very high stats and whatnot). I wasn't sure it would work but I've been eyeballing it pretty successfully. Specifically, the Pathfinder version of Rappan Athuk has run very well in my hacked 2e game.
 

see

Pedantic Grognard
Obviously things changed some between TSR versions, but there's a reason why the original Encyclopedia Magica, Wizard's Spell Compendium, and Priest's Spell Compendium multi-volume sets were able to provide every magic item and spell that had been published for any TSR D&D for use in 2e games.
 

ZeshinX

Adventurer
What do you think?

1. Do you think that the old TSR D&D games are largely compatible?

2. What is your experience, if any, converting TSR material to 5e? 3e material? 4e material?

Aside from 1e/2e being, mostly, identical (with a minimum of conversion work needed), I'd say the various editions aren't so much compatible mechanically as they are conceptually. You can take an older module from previous editions and convert it to whichever edition you happen to be running it in, but I'd bet most would require some significant tweaking, the ease of which would depend greatly on the person's system mastery between the two (or more) systems. So, certainly doable, but requires a fair bit of knowledge. Of course, going from 1e -> 2e (or vice versa) requires little to no significant changes (though there are some gotchas of course). I can't speak to converting anything to or from 4e though, as I skipped it entirely (just wasn't my cup of tea).

I messed about with (somewhat) converting 2e's nonweapon proficiencies into 5e (as I find 5e's skill system and lack of any real progression there) a huge weakness of 5e. We (my group) tried it using just the 5e skills as they were, but it was ultimately limited by the small (compared to 1e/2e/3e/PF) number of available skills.

The basic approach was that each 5e class would receive a starting number of profs equal to the number they currently get (so the "choose X of the following skills). We then used the class groupings of 2e (Warrior, Priest, Rogue, Wizard) as a guide to determine nonweapon (skill) prof progression for each class. So you had Warrior (Barbarian, Fighter, Paladin, Ranger), Priest (Cleric, Druid, Monk), Rogue (Rogue, Bard), Wizard (Sorcerer, Warlock, Wizard). We ignored the grouping of what nonweapon profs could be taken by what class. The 2e progression didn't work so well (as Thieves/Bards were not the skill monkeys they have been since 3e), so we just used a universal progression of 1 new skill prof every 3 levels, so each class would earn 6 skills/profs over their career (3rd, 6th, 9th, 12th, 15th, 18th). With 18 skills and lots of tool profs to choose from, it worked well enough.

As we played we realized we really over-thought it initially. We didn't need to convert so much as just add a new skill/tool prof every 3 levels (of the player's choice to foster nifty character ideas). We eventually changed it to one new skill/tool prof every 4 levels (based on character level, not class level) to slow it down slightly and to foster a team effort approach to using skills/tools (some skills are still more useful for all to have than others). Even with backgrounds and subclasses and MC'ing adding possible new skill/tool profs, we've found this to work pretty darn well.
 

There is quite a bit I disagree with about what you wrote, but this is something I wanted to pull out. While quality is a subjective issue, quantity isn’t.

There were far more AD&D adventures than BECMI ones.
If you combine both 1E and 2E as "AD&D," then you're correct. There were about 81 BECMI, 114 1E, and 111 2E. Interestingly there were a lot of 1E "adventures" that were just compilations of previous adventures (BECMI had a couple, but not many). If you take those out, 1E probably had a bit more than a hundred. I wouldn't consider these numbers to be "far more," although it was more than I recall (guess I happened to have more BECMI adventures).
 

GreyLord

Hero
1. I think TSR D&D from 1975-2000 was all compatible with each other. What people consider compatible now is far less compatible than the base systems of all those versions (OD&D to Core AD&D 2e). People find Pathfinder and 3.X compatible, and they have far more differences between each other than the old TSR games. People played and switched between modules and D&D forms all the time back then.

2. No, I don't consider TSR D&D 1985-2000 compatible with 3.X, 4e, or 5e today. One can change stats and other items, but nothing can be run as is and be compatible with the different versions. There are some that require more or less work if you want to run it for an another version (For example Castles and Crusades, though technically not D&D, is probably the easiest to run and convert 5e materials for, and as a crossover could be easier to convert Old D&D to as well. 3e and 5e are probably next in conversion, and then perhaps it is a tie between 3e and 5e to older D&D versions. 4e is probably the hardest to convert to any of the other versions).
 

TheDelphian

Explorer
My experience comes mostly from converting 4th edition Gamma world, the 199 edition which was pre 3rd edition post 2nd for D&D to 5th edition D&D.

It really depends on what your design goal is. I went for things being mostly recognizable but trying to bring things more into balance. I did not make things balanced though to be honest, I was shooting for more balanced not balanced.

So my intent was the sort of things a new group of PC's exploring the world would be expected to handle the same challenges. A Starting group fighting a group or Arks or Badders, a mid level group facing Serfs, and a high level group fighting big robots or a thunder lizard.

Systems very seldom are compatible but I think it is a more important matter of do the things I encounter seem reasonable. In keep on the borderlands do I expect my first through say 3rd level group to fight and survive the same against the same opposition. Can 1st level characters cut it in the kobold caverns. Sure lots of stuff would have to change but does so much change that it is no longer the same D&D or the same Keep on Borderlands.

I actually did the same conversion to 3.5 as well from same base. It was actually much harder just because of 3.5 complexity. So much interaction and cascade of effects. adding 2 Str to something effected so many things. 5th was a lot easier. I managed to hold to Bounded accuracy with the conversion though the range is bigger,for example a starting character in 5th is expected to have a +4-+5 to hit at 1st and a +10 - +12 or so at 20th at their main thing magic or weapon. IN my conversion that is more like +5-+6 up to +12 - +14 but still bounded somewhat. Everything is inched up accordingly. More Monsters with 16-20 Ac's and such. Hit point inflation is a little more but so is artifact damage.

But over all compatibility me is more about feel, impression and experience then how much numbers match or other factors.

I have wanted to post my GW conversion but then the whole racial issue occurred and I just didn't want to compete with the current much more serious discussions and issues that abound on the boards lately.

Just some thoughts.
 

Ancalagon

Dusty Dragon
I've run 2nd e modules in 3e, and I've run them in 5e, and it's far easier to convert to 5e than it is to 3e. I'm guessing it's... half the work? Maybe even less?

The main two things to remember is to have less magical item as treasure (SO MUCH TREASURE) but also that swarms of weak enemies are far more dangerous in 5e, with a goblin having +4 to hit instead of a thaco of 0 (ie +0 to hit), as an example.

Lastly, there is also an intriguing possibility that more than one set of rules are operating within the same world.... Super-heroes run 3.X or 5e, more "normal" heroes run B/X, and grubby ones run the GLOG.... The Goblin Conspiracy
 


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