Computer specifications

Generally, emulation runs off the CPU, with the GPU allowing for higher resolutions, AA, etc. If your CPU isn't good enough, you can't emulate a system too well. An Intel Core i5 2500K, 3570K or 4670K or above is recommended for high end emulation (e.g. PS2, Wii). This page will detail specific information for specific systems, if the above is not a viable option.

Enabling dynarec options also speed things up.

CPU

MegaHertz Myth

Just because a CPU has a high clock speed (e.g. in GHz) doesn't mean that it is powerful. For example, a 4GHz Pentium 4 is much, much less powerful than a 3GHz i5. Though "i5" is quite vague, as that could be any of the generations or models, P4s are just that weak. Newer CPUs are almost always better. Though the particular architecture does matter. A common misconception is that a higher CPU clock speed guarantees improved emulation performance. Although clock speed is one of the main factors for good CPU performance, it is not the determining factor. Newer CPUs generally perform better than older ones at similar clock speeds. For example, a 2.4GHz dual-core Intel Core 2 processor will generally outperform a 3.2GHz dual-core Intel Pentium D processor. Even though the Pentium D is clocked higher, the Core 2 Duo is faster due to the Core microarchitecture of the Core 2 Duo having so much higher instructions per clock than Netburst microarchitecture of the Pentium D that it can do more instructions per second despite having lower frequency. This is true of many modern Intel vs AMD processors, as the high-end Intel processors are more efficient than the high-end AMD processors. Main reason for that is because Intel processors have higher performing floating-point units, far greater cache/memory bandwidth/lower latency.

AMD vs Intel

Generally, Intel CPUs perform better than AMD CPUs for emulation in particular, due to their superior single core performance. AMD will still perform fairly well, but will rarely perform equal to a similar generation Intel CPU at the same clock speed.

Desktop vs. laptop

Laptop CPUs are typically much weaker than their desktop variants due to being clocked lower, for battery and heat reasons. They may also have less cores than desktop processors with similar names. For example, an i7 2-core laptop processor is most often weaker than a decent i3 desktop one. It's a common misconception that an i-whatever laptop is equal in power to i-whatever desktop.

More Cores

Emulators generally only utilize 2 cores (sometimes 3 or 4 with hacks), so having a hexa/octacore CPU, or one capable of hyperthreading, wont benefit you anymore than having a similar quadcore CPU.
Newer system emulators like RPCS3 can utilize more cores though, by emulating the system's thread scheduler it uses as many cores as a game makes threads.

Overclocking

Not every CPU can be overclocked, nor does every motherboard/BIOS support it. An advantage of the Intel K series is that they are unlocked and can easily be overclocked. Also, certain Intel processors such as their Pentium 20th Anniversary CPU are sold unlocked for a cheaper price than K-series chips, and while they may lack features like hyperthreading, they're capable enough especially for those who would like to overclock on a budget. Keep in mind that budget motherboards e.g. certain Haswell H and B-series boards from ECS and ASUS only have options for setting the processor's multiplier and not voltages. Also, Intel may block overclocking on non-Z series boards in future microcode/BIOS updates. So if it can't play a game currently then you can, in many cases, overclock it until it is playable. Laptop CPUs often cannot be overclocked due to BIOS limitations. Extreme or incorrectly-done overclocking can cause instability and hardware damage. If the emulator starts having problems try again without overclocking.

Some motherboard vendors, notably ASRock, took the extra effort of trolling Intel by using an external clock generator in order to circumvent restrictions on non-K Skylake CPUs.

GPU

GPUs are basically just hundreds of underpowered CPUs on the same die. Or you can think of it as a 300 core CPU.

The thing is with 3D graphics is you can split the work up into hundreds of different parts and give each piece to a different core on the GPU since it doesn't matter which order the pixels are rendered in, as long as they all get rendered for the same frame before moving on to the next.

File compression/extraction and bitcoin mining are also good examples of programs that can make use of parallel processing.

However, most programs can not do this. Dwarf Fortress for example can't make use of a graphics card, because every calculation it does is dependent on the one done before it. That obviously doesn't work if you try and do them all at the same time.

Pretty much any emulator is the same. It can't know what comes next until it's done what preceded it. It has to run on a single thread. It still needs some form of graphical output to output the final rendered 2D screen alone. This can be done via a GPU to put the 3D graphics on the screen, but any emulatable system shouldn't be too taxing. This is called "Hardware Rendering". Alternatively, all of the graphics processing can be done on the CPU, and will be more predictable/consistent for it, but that is also costly. This is called "Software Rendering".

Most 3D emulators have hardware and software renderers. Software renderers use much more CPU power, which may be slower. They may also run on their own threads separate from other emulator parts, which would likely reduce the performance loss, but the CPU must still be strong enough in the first place.

Recommended Specs

PCSX2

Minimum:

• Windows Vista / Windows 7 32-bit/64-bit
• CPU: Intel Core 2 Duo @ 3.2 GHz or better
• GPU: 8600 GT or better
• 1GB RAM (2GB if on Vista / Windows 7)

Recommended:

• CPU: Intel Core i5 2500k, i5 3570K or i5 4670K

For those with DualShock 3 controllers, use the new XInput Wrapper SCP.

Dolphin

Minimum:

• 3 GHz+ Intel Core 2 Duo CPU
• DX10 GPU
• 2 GB+ RAM

Recommended:

• CPU: Intel Core i5 2500k, i5 3570K or i5 4670K
• GPU: Nvidia 8800GT equivalent or better
• RAM: 4 GB+

See the Dolphin page for further recommendations, such as controller setups.

Mednafen PSX

It is generally recommended that people have an Intel Core 2 Duo @2.0GHz or better for good performance with this emulator.

Higan

bsnes - Performance and Balanced

A 2.0 GHz Intel Core 2 Duo will run most games full speed.

bsnes - Accuracy

A 3.0 GHz Intel Core 2 Duo or better.

DeSmuMe

• Windows Vista SP2 or later
• Mac OS X: v10.6.8 Snow Leopard or later
• Linux: Any recent Linux distribution with a 2.6 kernel.
• 3.0 GHz Intel Core 2 Duo CPU or equivalent
• 2GB+ RAM

Enable the dynarec option for speedups.

PPSSPP

• Modern CPU
• OpenGL 2.1-compliant GPU

Enable the dynarec option for speedups.