ATX or Micro ATX?

How does a ATX case differ from a Micro ATX case?

I have a HP Pavilion model 7955 and it’s a small tower (only 14.5" high).

Today the techie on “HP Live Chat” told me I have an ATX case, not a micro ATX. But for some reason I had in my mind that I had a Micro ATX because of it’s size. So I’m confused as usual and need your help to set me straight.

The reason I’m asking is I want to upgrade my little 200 watt power supply (Bestec ATX 1956D) to at least 300 or 350 watts.

My current Bestec PSU measures 5.9" W x 3.4" H x 3.9" Deep and that sucker is so tight in the case I need to get an exact “same size” replacement…or it just won’t fit in my case. No foolin…anything bigger will not fit.

  1. What’s a good brand of PSU? Who sells them for a good price on line?

  2. Do all PSU’s have the same output voltages and amps?

  3. Do all mobo’s require the same voltages/amps? If not, how will I determine what I need?

  4. Besides fit…what should I look for in a new PSU?

I need a little help from my friends…

Thanks guys…and yes I’m still screwing around with this 4+ year old HP.

It’s smaller (obviously). An ATX size board will not fit in a Micro ATX case, although I believe that a MicroATX board can be used in an ATX case.

Similarly, a micro-atx power supply is physically smaller & has reduced power output. You can use a standard atx power supply on a micro-atx system if you can squeeze the PSU in :wink: (which you can’t).

You will have to find a micro-atx power supply of those sizes, which is likely expensive, or change your case to a standard ATX case & fit a relatively inexpensive PSU.

See above.

I’ll leave this to someone else.

Voltage-Yes. Amps No. Higher “Wattage” rated PSU’s can supply more amps. Voltages will be the same.

Power = Volts * Amps.

A higher wattage is better, within decent brands. Cheap brands will advertise higher wattages, but the components are cheap, and the fluctuations in voltage can kill sensitive pc components.

Yes. It’s called a standard.

Stable voltages. Large fans. Lots of large size conductors to devices.
Excellent online reviews which actually check the voltage stability, rather than just saying “It has pretty coloured cables”. A few SATA power connectors also wouldn’t hurt.

My personal advice is to swap cases with a full atx case, unless it’s a home entertainment unit.

I’ve decided to start from scratch and build what I want. I’ve wanted to do this for a long time now…so I’m forgetting about the upgrades for my HP.

I’ll most likely need your help along the way.


Microatx is for small form factor computers only.

ATX is the standard sized.

I’m thinking of going ATX mid-tower case.

Just a remark debro before this gets totally confusing. :confused:

Micro-ATX has nothing to do with “small form factor computers”. SFF mobos are known as “Mini”, Flex/Micro-ATX, Mini-ITX, (example SFF).

ATX and Micro-ATX can be very similar in layout and onboard futures. Compare ATX with Micro-ATX.
Micro-ATX results in a shorter mobo, ie. you miss a few PCI (and maybe also PCI-Express) slots.
Mobo size, ATX=12"x9.6", Micro-ATX=9.6"x9.6". :slight_smile:

Apologies for not clarifying … (something which seems to be becoming more common).

Expansion is always a good thing … and people will really gain nothing by using a micro-atx board, if all they want is a standard computer.

The micro-atx boards are really only useful if you want a smaller form factor PC (or intend to use it temporarily as a full sized PC and “downgrade” the size later), as the Micro-atx boards generally skimp on upgrade options, like extra ports & upgrade slots. Additionally, if you want to dabble with “advanced” hardware options like overclocking, you are getting the short end of the stick. They just aren’t designed for hard-core enthusiasts :wink:

Of course, the boards can still be quite decent, but just not the best way to go for most people :wink:

Hmm… MATX motherboards are usually the same as an ATX with the exception of 2-3 PCI slots instead of 5 which you probably wont use since pretty much is onboards.
There are several MATX motherboards which allows the same overclocking as ATX motherboards so what are you talking about?

Yes, mATX are usually the ones with onboard graphics, so since you’re not in to gaming, an onboard nForce or ATI video-chip can be just perfect for your needs (saving you the cost of a separate video card). These boards fit just as well as ATX boards in a Mid-Tower case.