Urgent help please. Assembling PC

What case and what motherboard?

CPU cable question: in most cases, use just the 8 pin with the CPU label on the cable. It is designed to split apart into 4 pin so that motherboards that have CPUs which require less power can be compatible.

PERIF cable question: don't worry about it. This is used for adjusting pins in case something isn't compatible.

Case fan question: plug the 4 pin power one into the motherboard fan pins. If you don't have enough, then use the molex. There's no need to connect both. The preference is to plug into the motherboard so that it can auto adjust the RPMs.

The CPU cable is to provide power directly to the CPU via its own connector on the mobo near the CPU. It is in addition to the big (22 or 24-pin) main power connector for the mobo.

The "Perif" cable probably carries a few female connectors each about ¾" wide with 4 holes in a straight line, usually called 4-pin Molex power outputs. They were originally used to provide power to peripheral devices like 5¼" floppy drives, IDE HDD's, and optical drives. Most peripherals in use today no longer use them, having switched to the SATA power cable form. But some devices still use them. This cable set may also include a smaller 4-pin female connector that was used for the smaller 3½" floppy drives.

For your case fans, the female 4-pin connector is to be plugged into mobo SYS_FAN port(s). They should have little ridges on one side in line with the first 3 pins so that it can only be plugged in one way. The larger 4-pin Molex connector probably has only 2 wires to it, and it provides power to the LEDs separate from the power to the fan motor. THIS is why you need 4-pin Molex ("Perif") outputs from your PSU. One thing you should be aware of is that PSU Molex outputs can supply a lot of power, so you can connect all the fans' LED connectors to only one Molex supply if you want - you just need Molex-to-Molex power splitter adapters.

Regarding fan power, most mobo SYS_FAN ports can supply up to 2 fans per port via a fan splitter adapter, not not more. That can be useful if you have more fans than ports.

A bit of info on mobo fan ports. You will have one CPU_FAN port that you really should use for your CPU cooling system (fan or whatever). You MAY have an additional CPU_OPT ports (or some similar label) for a second fan for the CPU if you had one. These ports can provide automatic control of the CPU cooling system fan speed if you let them (the default setting) based on temperature measured inside the CPU chip itself. Your mobo also will have one or more SYS_FAN or CHA_FAN port(s) to power case ventilation fan(s). The automatic control of these is based on a different temperature sensor built into the mobo. If all your fans are 4-pin type (with 4 wires to each motor), that means they are of the PWM design. IF there is any option in BIOS Setup for setting the mode of operation for the mobo fan ports, they should be in PWM Mode (NOT Voltage Control Mode) to run those 4-pin fans.

Your mobo MAY have a fan port (usually with 3 pins) labeled PWR_FAN. This is designed for a specific purpose that may not match your system. SOME PSU's have a set of 3 wires (Black, Red, Yellow) coming out and ending in a female 3-pin fan connector. IF you have this, plug it into the mobo PWR_FAN port. Its sole function is to let the mobo know the speed of the fan inside the PSU, just in case you care. It does not actually control that fan's speed. IF your PSU's internal fan has some automatic speed control on it, that is all done inside the PSU itself. If your PSU does not have those leads coming out, normally you would plug nothing into the PWR_FAN port. But this port often has power available on its Pins 1 and 2, but with no control over that. So some people use it as a supply for a fan to run full speed all the time.

no need to worry about the pins. they will fit in the socket they are ment to fit. so go for it no need to worry about anything.