Chain casting is an action where multiple spells are cast in succession with minimal delay between them. This is a
crucial skill in raiding, where (provided that the person does not upset a mob's threat table) it
improves individual performance, whether tanking, healing or dealing damage.
There are striking
similarities between how one chain casts and how a
computer's processor works. The following will draw parallels between the two, and may allow the chain casting process to be treated differently to frantic
button-mashing. It would be important to know that the
central processing unit (CPU) is the component of a computer that follows a series of instructions to produce a series of results. Only spells with cast times of some multiple of the global cooldown will be considered.
Processing an instruction <--> Spell castingThe
instruction (in computing) is the
atomic unit of a CPU's entire workload. the CPU can only digest
one instruction at a time (though if it has
n cores, it can process
n instructions at the same time), and will do so
in sequence.
When
casting a spell, the player
selects a target, decides which
spell to cast and
presses the appropriate button (in any order). The player does this
repeatedly and
sequentially while chain casting.
Clock generator <--> Global cooldown
A crystal oscillator which can provide a clock signal to a computer system.By itself, the CPU has
no concept of time and thus cannot process instructions (which take time). A
clock generator provides a rhythm (the
clock signal) to the CPU. As a certain amount of time passes between beats (
clock cycles), the CPU can use this rhythm to
perceive time. It will then
process however many needed instructions in a clock cycle (or vice versa). The frequency of the clock generator is measured in
hertz (Hz), or cycles per second.
The
global cooldown (GCd) is the minimum time that needs to pass between spell casts, which (when not modified by Haste Rating or
Bloodlust/
Heroism) is
1.5 seconds. This corresponds to a
frequency of 2/3 Hz. (As a side note,
Haste Rating can reduce the GCd to 1 second and increase the frequency to 1Hz.)
This GCd can provide a rhythm which avoids the need for button-mashing. Some
long-cast spells (e.g.
Greater Heal) take whole
multiples of one GCd to cast, which can be spread over several multiples without losing the sense of rhythm (simply miss a few beats).
Clock multiplier <--> Chain casting ability
An interface showing a system's system clock settings.The
clock multiplier multiplies the clock rate by a certain number
n, so that the clock signal actually used by the CPU is
n times faster than the clock signal from the clock generator.
A novice player may be able to cast
1.5 second spells over 3 GCds (frequency of
2/9 Hz), which, if the GCd was used for the 'clock signal', would cast on a
'clock multiplier' of ~0.33.
Overclocking and resulting overheating <--> Practice and resulting fatigueOverclocking the CPU involves setting its
clock multiplier higher. This
hastens the clock signal in use and causes the CPU to
work faster. However, by working faster, the CPU also
generates more heat. If it cannot withstand the heat, it will start
introducing errors in its work.
With practice, the player can chain cast close to the
maximum 'clock multiplier' of 1. However, if they keep this up, they will get
tired (if done repeatedly, they may suffer
burnout). In normal raiding, the
practical maximum is not usually needed, and the player can afford to work suboptimally to keep their energy levels up.
Interrupt handling <--> Situational awarenessA (software)
interrupt is an instruction for the CPU to stop processing a set of instructions (a
process) and start processing another. It allows a single CPU to run several processes at the same time (
multitask) by simply
switching between them.
Raid encounters rarely involve simply casting spells at fast as possible. There are almost always
random events to respond to. The player would chain cast as normal, then
interrupt it to
respond promptly to events needing attention. For example, a tank healer responsible for two or more tanks would need to switch constantly between them, devoting most of their attention to the target tank. Some attention would be reserved for recognising the healing needs of the other tank(s), as well as responding to the environment.
Something to considerA Brunel University study found that
working to a rhythm reduces fatigue. By
casting in time with the GCd (or some other rhythm), less energy will be used and the player will be able to more easily sustain their performance in a raid.
