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In Reply to: RE: P24 current measurements. posted by gene_ on November 22, 2009 at 07:47:59
Hi Gene_,Thank you for demystifying the ATX start-up process and for sharing on the Audio Asylum forum. You showed the way to a full linear cMP2 power supply !! Thanx you very much.
I have a question about timing the PWR-OK signal and a question about using a relay to switch the PWR-OK signal.
-> Question about timing the PWR_OK signal
The ATX formfactor says:
- the timing has to be: PWR_OK delay 100 ms <- Timing <- 500 ms.The +5V Power_Okay signal should be switched to pin 8 within 500 milliseconds. How do you do that by hand?
Or…… is it not so critical after all? And can it also be done by hand? Even after 1, 2 or 3 seconds?
-> Switching PWR-OK with help of a relay?
I was thinking of switching the +5V PWR_OK signal to pin 8 (grey wire) with the help of a relay (with some time delay).
This relay acts on pin 14 (green wire)the PWR-UP signal.- Idea.
* First: normal ATX PSU start-up proceeding
You power pin 9 (purple wire) with +5 volt because the Power Control Circuit (PCC) on the MoBo reacts on pushing the start-up button.When the PCC is active (+5 volt on pin 9) and the start-up button is pressed, the PCC than will drop the power on pin 14 (green). No power on pin 14 (green wire) signals the ATX PSU to power up.
When the ATX PSU has it’s power up, the ATX PSU than gives +5 volt to pin 8 (Grey wire). With +5V on pin 8, the PCC now starts the processor.
* Giving PWR-OK signal when using all linear PSU’sSwitch on 3.3, 5 and 12 volt to P24.
Which also powers pin 9 (purple wire) with +5v (standby function). This way the Power Control Circuit (PCC) of the MoBo is active and thus also pin 14 (green wire) gets +5Volt from the PCC.When PCC is active and the start-up button is pushed, the +5V on pin 14 (green wire) is dropped by the PCC. This causes the relay to switch +5V to pin 8 (grey wire) as PWR_OK signal to the PCC.
With PWR-OK signal on pin 8 (+5V on grey wire) the PCC allows processor to start working.
Since the 3.3, 5 and 12 Volt is already switched on as being the first step, the processor will have no problem starting.
I was brought to this idea because some websites also say:
"Some extremely el-cheapo power supplies may "fake" the Power Good signal by just tying it to another +5 V line. Such a system essentially has no Power Good functionality and will cause the motherboard to try to start the system before the power has fully stabilized.”
http://www.pcguide.com/ref/power/sup/funcPowerGood-c.html
Do you (or any other inmates) think this could work?
fully AOB optimized cMP2 PC -> Lynx AES16 -> XLR AES/EBU -> Lavry Black DA10 -> XLR Mogami Gold -> Klein & Hummel O300
Edits: 11/23/09Follow Ups:
Hi Mark,
I am also read about poorly designed ATX PSU, it is incourage me to try .
I am was not sure sistem will be restarted but it did. I use more switches as a heritage from previous set up. My set up proove -3 switches enough ( not take in account -12v) , HDD, Rest of voltage, Power Good. I did try minutes ago deferent combination - All voltage
without HDD , then HDD then Power Good and it started !
So, we can expect two switches will be enough. Remember ' cheapo 'ATX ?
Mark, of couse, relay can give you convenience of remote control power.
I placed switches on front panel, so it convenience to use , look as standard HI-FI chassis.
About ATX factor standart. Maybe hardware manufactures not forgot about us :-). I was give to MOBO by mistake -1.8v instead of positive
voltage , power up cMP^2 complite - nothing happen.
Best, Gene.
Hi Gene_,
Thank you very much for your reply. Your reply encouraged me too also try to give the PWR_OK signal by hand (manually).
Since I already had a modified P24 extension cable which I used for the P24 current measurements. I put a little black switch on pin 8 (power good, grey wire). See photo. For simplicity reasons, I put the ANTEC Earth Watts 430 on the P24 extension cable to power the MoBo.
Giving the PWR_OK signal manually on pin 8 (grey wire) at P24 connector. cMP2 project.
With 230 AC on the ANTEC Earth Watts, the ANTEC provides a +5 Volt stand-by signal on pin 9 (purple wire) for feeding the PCC (Power Control Circuit) on the MoBo.
When the PCC is active it gives a +5 Volt on pin 14 (Power ON, Green wire) to the ATX PSU, which signals the ATX PSU, NOT (!) to power-up.
When the Power Button is pushed, the PCC drops the power on pin 14. No Power on P14 is the signal for the ANTEC Earth Watts to power up.
But because of the switch I placed on the grey wire (pin 8), the ANTEC Earth Watts can not give a Power Okay (PWR_OK) signal to the PCC on the MoBo. Although the ANTEX powers the 3.3, 5 and 12 Volt rails, there is no signal on pin 8 (grey wire), thus the PCC will not start the PC.
When the PWR_OK signal on pin 8 (grey wire) is given manually with a switch, the PCC starts the PC. The PWR_OK signal can be given manually at any desired time, provided there is power at the 3.3, 5 and 12 Volt rails. Giving the PWR_OK signal manually on pin 8, is indeed not time critical(on my GA-G31M-ES2L MoBo)!
Thank you for sharing on the forum! The road to an all Linear powered cMP2 PC is open !
Mark
fully AOB optimized cMP2 PC -> Lynx AES16 -> XLR AES/EBU -> Lavry Black DA10 -> XLR Mogami Gold -> Klein & Hummel O300
Hi Mark,
I am happy my experience was useful for you. I am pretty long time
read yours and another CiCs followers post on this forum so maybe it is
just evolutional devolopment :-)
One another tips for " warm" start. I use 12v-20WA spot light balb, placed on CPU and connected to 5V stand by , so it will heat CPU to 37'C all time. Need one more swich or interconect for disconnecting.
Best ,Gene.
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