When is more cores and GHz bad?

more ghz and cores is always good, however that is not the only thing that dictates a processors performance. For example a 2.4ghz core 2 duo is faster than a 3ghz pentium 4 dual core.

As iam2thecrowe said, it's never bad to have too many cores or more ghz (expect for when your Blue sceen of deathing the computer).

Although there is a point were you wont notice a difference between a lower core count/ lower Ghz cpu compared to a higher cpu. That would be due to the apps cant use all the cores and/or the cpu able to complete the tast fast enough that it not mattering.

Generally speaking, the more GHz the better. Also, the more cores the better as long as the program or game can make use of multiple cores. Right now most games only need two cores, some can use 3 mores, and few can use 4 cores.

The bad? Well that would be:

1. The game or program does not use all the cores in your CPU.
2. More GHz and more cores means more $$$.
3. More GHz and more cores means more heat.
4. More GHz and more cores means more electricity.

General tips:

1. Intel CPUs cost more than AMD CPUs because they perform better.
2. Build a computer around an AMD CPU and compatible motherboard if you are on a budget and can't afford to spend approximately $100 more for an Intel CPU and compatible motherboard.*
3. Buying a six core AMD CPU is a waste of money unless you use programs that you know can use all those cores.
4. Do not buy an Intel i7-2600k because games and the vast majority of programs used by ordinary users do not HyperThreading capabilities.
5. If you need to ask what is HyperThreading, then you definitely don't need it.

* That can go up significantly if you are looking a premium CPUs and motherboards. The Intel Core i7-980X Extreme Edition 6 core CPU sell for $1,050 and it is extremely fast compared to AMD's fastest 6 core CPU; Phenom II X6 1100T Black Edition which sell for around $190.

He is right I cannot feel any difference between my pentium p6100 and my brothers expensive i5 520 laptops. I use internet watch movies and songs and use itunes and office and play some games. Do not buy an i5 or i7 if you do what I do. A pentium will be fast enough or i3.

If you're on a desktop and you don't care about how much electricity you use or how much heat you put out, more cores and higher clock speeds don't normally hurt. (I've heard that when you get to around 16 cores or so things start to get worse, but that's most likely irrelevant to your inquiry). On laptops, more cores and higher clock speed generally mean less battery life and a hotter lap. The other posters have summed things up nicely.

why invest in horrid technology though? cause its good enough? well it might be ok now but is 3-5 years will it be ok then too?

^ I wouldn't say horrid as much as crippled. After all, Pentiums are now just crippled i3s (no turbo, no HT, less cache, no turbo) and i5s are just slightly crippled i7s.

Anyway, it depends on what's good enough for you. For example the new llano based laptops offer pretty good gaming performance for $500-$800 laptops even if the CPU side is weaker than their sandy bridge based competition. Of course, once you start adding dedicated GPUs it's in the favor of Sandy Bridge but certainly not weight or battery life  .

oh we are talking new sandy bridge pentiums now. i see, well thats not as bad then.