This page is  about PC standards,   (DESKTOPS ONLY)

The pins (headers sys 2 x 5  to 2x16) are all non standard for front USB (wired) front panel I/O , power switch and all things not show below that needs to be plugged in.
The front panel jacks for USB are not really standard but if the maker uses Intel spec for this then it is. (most things on the front panel wired are custom (not DVD)
There is no standard BIOS or OS. Below is hardware only.
Non standard fans on many of which fail for RPM , not using real fans from  Dell or not from HP, etc.   (but top ASUS board I can use  a 4 pin fan and tune the fan as I wish in the fine BIOS there "Z270p up")
Most these OEM  PC do a hard P.O.S.T error with non OEM parts installed or missing , wrong fan, missing thermal sensor or missing I/O panel., cable detect sensor fail, chassis intrusion and case lock solenoid missing. (and more)
My HP600 has all pin-outs told but  power jack.(power and 3way  power LED status is not documented.)
The OEM PC has many things inside that are totally custom to them and all model series of PC.
The Case can be custom and use non ATX parts (or any) non-standard   mobo hole spacing. (mobo = motherboard)
This  example below, is Asus, and is custom to them only, these pin headers. example. Many top maker of PC like Dell or HP do not document this at all,  they just tell you to plug it in as it is keyed only one way.
Example 2x10=20" (even Asus is not consistent here , model by model or series MoBo)
Click here to see my Dell 3020-MT , photo marking non standard connections.

The exception is on high end OEM workstation PC with full pin out documentation in the service manual.
I have Dells (5/6) pin power jack here, for Dell 390/3020/T3610,7010/9010 and more. just power on pins , the other pins are 2 complex  BiPOLAR LED pins.  Jump pin 5 to 6 powers it on. (one more) from RU (cable view).

ALL Standards used in this industry PC. (most common now.)

The mobo and case come on many standards ATX old and MATX (mini-ATX) are common and BTX is junk never use BTX.
The 24pin power jack is standard as is the 4 pin square plug  for CPU (VRM = voltage reg. modules),

The wiki covers each do that?  Google "wiki USB " or wiki PCI-express."+
USB jacks (externally) are standard USB1 up to new USB-C (and downward compatible, USB-c needs adapters to do  that)
PCI-express slots are a standard. 1 to 16x  (an x1 card up  can work in x16 slot) 
SATA data  ports are standard to DVD , HDD or SSD.  (needs power to 15pin cable below, from PSU)

The ATX SIZE PSU IS A STANDARD, and is best of gaming. (700w best) 150x140x86mm sized. (or longer ) see photo spec below.

Some find cases sold (top DYI brands) have holes that allow many different standards, ATX/mini and micro and more, (shop as you wish)

Photos of standards below;

Power is first.  Molex power connectors. (all)  20pin is now fully obsolete. 24 is below.
the jumper is for bench testing any PSU .

The 15pin SATA power cables are a standard. (for HDD/SSD and DVD)

GPU card power, for over 75watt GPU  cards here. 

Next up is PSU case size ATX,  Lengths(deep) do very long over 700watt.  (mm sized, to see inches divide MM by 25.4)  (86 tall,  140mm deep (min) and 150mm wide is spec)
PSU  standard ATX If gaming buy only PC with real ATX PSU so you can upgrade

ATX CASE SPEC , HOLES: (2004 UP) CLICK BELOW PHOTO TO ZOOM IT. (inches) x 25.4 for MM.)


BTX form factor is a hard failure. The wiki covers this.
  • 2 fan mounting  holes missing (needs custom  BTX case and a very queer fan shroud /mount from H3LL) AVOID THIS.
  • Fan hits GPU card, heat sink. (NO FAST  CARDS FIT)
  • Mobo is A backwards a mirror OF  ATX or far far worse. pico sizes etc. so will never fit any ATX case.
  • The silly mobo has  the x16 slot such that it hits other cards on other slots wow, no fun there.
  • And is a failure. Intel ended it in 2006, but Dell made many (sadly) and HP compaq, 8100, RIP BTX !  (AVOID FAILURES IN LIFE LIKE , YUGO CARS, And Isusu Suzuki, and this BTX junk.
USB front jacks and cables are not a standard the closet they come is to the diagram, (many PCs use all custom cables here) Some even have presence detector,)

version 1.  10-1-2020