Hi, Just a quick question. Is it just my memory or is the mob spawner spawn rate was a lot a couple of years ago? I remember that if you didn't quicly destroy the spawner, you could get submerged fast. I used a lot of mob grinder with spawner in the past to get quick XP, but it's now almost not worth the waiting.
Mobs from spawners have disabled AI after the first few waves. The spawn rate is the same. The entities that can exist in an area has been lowered though. (75 to 5x5 chunks)
I've been playing minecraft for almost 9 years and I remember that I had done a zombie mob grinder with 2 spawner. I had to change the gameplay to (peacefull) because after a a minute or two, the entire game was so much lagging that I could reach the spawn to destroy it.
Vanilla rates depend on your own CPU, while server rates have been reduced to diminish lag. As Luckygreenbird said above, only 75 entities can exist in a 5x5 chunk square. (In this server: EmpireMinecraft) More details can be found here: https://empireminecraft.com/wiki/changes-from-vanilla-minecraft/
