Final Fantasy V/Bugs

This is a list of bugs known to exist in at least one version of the game. Since the game was released on three different platforms over a long period of time, and patched copies of the ROM are available to use with emulators, some bugs may have been fixed in your specific version. The details here may get rather dull, but the "Overall effect" section should explain what the bug means to the average player without a lot of explanation.

Presumed intent
This is a bug in the way the game computes damage when you attack with a Knife type weapon. For sword type weapons the character's Vigor is used to determine the attack multiplier, which is the ratio between the value of an attack and the actual damage done to the target. Apparently the idea was to increase the attack multiplier for knives based on the character's Speed, partly to compensate for the relatively low attack values for this type of weapon, and partly to make these weapons desirable for Jobs with high Speed values such as Thief. Specifically, the attack multiplier for Sword type weapons is:
 * Sword multiplier = 2 + (Level * Vigor)/128) [drop any fraction].

Presumably the multiplier for Knife type weapons should be
 * Knife multiplier = Sword multiplier + some fraction of (Level * Speed).

Call the increase you get from the Sword multiplier to the Knife multiplier the "Speed bonus",

Actual behavior
In fact, the Speed bonus you get for the Knife multiplier is always either 0 or 1 and does not get proportionately larger as you level up. The actual formula depends on the remainder when Level * Speed is divided by 256. If this remainder is between 0 and 127 then
 * Knife multiplier = Sword multiplier

and if the remainder is between 128 and 255 then
 * Knife multiplier = Sword multiplier + 1.

Overall effect
Because the Speed bonus depends on level, the bug doesn't actually have any effect until you reach about level 11. After that the effect becomes more and more serious and a high levels Knife type weapons become much less powerful than they were presumably intended to be. In particular, this makes the Thief job less useful than it would be later in the game since you would normally equip a Thief with a knife.

How to tell

 * 1) Play the game to level 6
 * 2) Change a character to Bare and equip with a Broadsword.
 * 3) Find an area with easy monsters and, when in battle, attack one whose Def. value is 0. Steel Bats in the Pirate Cave make a good choice for this. Make sure you're attacking from the front row and the target is in the front row. The damage will be either 45 or 48. Since the attack value for the Broadsword is either 15 or 16, this means that the multiplier for the Broadsword is 3 = 45/15 = 48/16.
 * 4) Change the weapon for your character to Knife.
 * 5) Attack the same monster; this time the damage will be either 28, 32, 36 or 40. Since the attack value for the Knife is from 7 to 10, this means that the multiplier for the Knife is 4 = 28/7 = 32/8 = 36/9 = 40/10. The Speed bonus is then 4 - 3 = 1.
 * 6) Continue to play the game to level 11.
 * 7) Again, change a character to Bare and equip with a Broadsword.
 * 8) Go back to the same area and attack the same monster. Now the damage will be either 60 or 64. This means that the multiplier for the Broadsword is 4 = 60/15 = 64/16. The increase is due to your leveling up.
 * 9) Change the weapon for your character to Knife.
 * 10) Attack the same monster again; this time the damage will still be either 28, 32, 36 or 40, which means the attack multiplier for the Knife is still 4. Now the speed bonus is 4 - 4 = 0. If you compute the Knife multiplier this way and get 5 or 6 then the bug has been fixed in your version of the the game. Note that the bug prevents any increase in damage even though your character has increased five levels.

Source

 * |FFV ALGORITHMS AND STATS FAQ by J.L. Tseng, 2004, on GameFAQs.com.