Block IDs and item IDs

[ThePagan]

I just finished going through all my configs and writing down which mods are claiming which IDS. When I first put my modpack together it gave me some conflicts, which I now assume where BlockID conflicts. I've noticed some item ID conflicts recently which prompted the tedious task of writing all the IDs down. I then compared the ID number from the configs to the ID's shown through NEI. Some were 256 higher in NEI than in their config. The lowest ID I found this on was 5000 and the highest ID that didn't offset was 18976.

I was wondering if someone could explain what the 256 offset is caused by and why only a few of my mods are not affected by it. Also I was wondering if conflicts are only caused by the NEI shown ID or if config shown IDs can cause conflicts as well.

What is the max itemID, as the highest one shown in my pack is 30516? This is all for forge on latest build for 1.6.4.

[Chefsbrian]

I couldn't tell you why your reporting discrepancies in all this (I haven't seen it myself in any of my private little packs) But I can tell you I usually dodge the issue by using the NEI as the first mod in the pack. Solving its conflicts work in ALMOST every case... The other cases where non-critical bugs (Item crafting with seeds instead of gold for some reason, but irrelevent for private use)

[planetguy]

The 256 offset is to make space for blocks, back when there were 256 blocks. Items are sometimes identified by their unshifted IDs, which start from zero. Where blocks can also be selected, items are identified by their shifted IDs, which take into account the IDs reserved for blocks. Most mods' configs use unshifted IDs, while some (such as Forestry, I think) use shifted IDs. Forge logging uses shifted IDs.

If you want to find all the conflicts in a modpack quickly, search the Forge log for "overwriting". Note that some mods overwrite vanilla things and/or their own ItemBlocks normally.