Test MOTHERBOARD w/o CPU ??? It's possible?

[GEOrifle]

Hi, i have ASRock 775i65GV which supports 775 CPU wich i don't have, but i got RAM,Memory, PSU, Graphic card, HDD .
It's possible to test MOB without CPU ? I don't wana spend money for faulty MOB and buy CPU .

 

[LokutusofBorg]

You need four things to POST: power, processor, memory, video.

You can certainly plug power into your mobo and test that it gives the proper POST codes indicating it won't POST... You're not going to get much beyond that. You can't get into BIOS without a CPU AFAIK.

 

[tcsenter]

POST does not require RAM or VGA (though it will not complete without RAM), but it does require a bootstrap processor. No CPU = 100% non-function.

 

[imported_Harbinger]

I guess you'd like to somehow borrow a cpu from a friend or something for a quick test. Otherwise what Lokutus said. Even without the cpu the pc should attempt to post and ideally beep beep that cpu is missing (might report that cpu is faulty, same thing pretty much in your case).

 

[LokutusofBorg]

Originally posted by: tcsenter
POST does not require RAM or VGA (though it will not complete without RAM), but it does require a bootstrap processor. No CPU = 100% non-function.

If you don't have RAM in the computer you'll get beep codes (how can you say it doesn't need it but it won't complete without it? /boggle). If you don't have a video card in the computer you'll get beep codes.

That's all I meant. Without those four things you can't do anything with a computer except listen to beep codes. If you have those four things you can at least get into BIOS.

 

[tcsenter]

Originally posted by: LokutusofBorg
If you don't have RAM in the computer you'll get beep codes (how can you say it doesn't need it but it won't complete without it? /boggle).

POST consists of numerous individual tests and sub-routines that are executed by the CPU. Without a CPU, there will never be any POST. Here is a mile-high overview of power-on for standard x86 architecture:

After the CPU receives the correct reset signal and power, it starts itself in x86 real mode and will automatically access its reset vector. The reset vector is a default physical address containing the first instruction executed by the CPU. For all x86 processors in the past 10+ years, this address is 0xFFFFFFF0, which is mapped to BIOS ROM by the core logic. This address in BIOS ROM contains a 'jump' instruction to another location mapped to BIOS ROM, which contains the starting point of the actual BIOS bootstrap routine.

The bootstrap routine contains instructions required for early bring-up of the core logic, CPU, TLB, FPU, MSRs, MTTRs, interrupt controller, among other things. The DRAM controller is one of the last things to be initialized because you need to bring-up other things first. e.g.

Since DRAM initialization is one of the more likely points of failure during POST, it would be good to have debug output capability via serial port before DRAM initialization. The serial port is almost always provided by the Super I/O chip connected via the Southbridge LPC interface. Therefore, in order to get a serial port working, you need to bring-up some of your Southbridge, too.

Not having those other things will cause POST to halt at some point. Without a CPU, you will never get to any POST. The system will be 100% non-responsive at any level.

 

[tcsenter]

Originally posted by: GEOrifle
It's possible to test MOB without CPU? I don't wana spend money for faulty MOB and buy CPU.

Cheap solution for this problem:

http://www.starmicro.net/detail.aspx?ID=603

 

[Zap]

Originally posted by: tcsenter
Without a CPU, you will never get to any POST. The system will be 100% non-responsive at any level.

This is true. I don't know why the idea persists that a motherboard should do something interesting w/o a CPU... kind of like thinking that an ATX power supply should turn on when they have power plugged in to it and flip the switch on the back. 😕

:thumbsup: Not a dumb question and it was answered.