HP 8740w - Combined load can't pull more than 213W

[triturbo]

Recently I got a new i7-920XM and a GTX 980m. The CPU because the old 920XM degraded and I had to pull back the clocks and the GPU because I couldn't manage to run the DreamColor with the GTX 1070. Now all is fine (or so I thought), because I finally have picture on the internal screen. The thing is - before, I dialed back the CPU and the 1070 was limited to 90W, so the performance was pretty good and never passed 195W (from the wall). Now - the CPU can do ~107W @3.5GHz (~145W from the wall) and the GPU ~115W @stock. These are values on their own. However if I want to push them together, they top @213W from the wall. I tried the Omen 350W (with custom made power plug) and the Slimq 330W with all 3 power plugs (two 330W and one 240W (the lowest performance ~195W from the wall)). The laptop has over current protection, but I thought that it would kick later/higher. So, the question is, other than running thick wires from the socket to the MXM slot (I don't want it since I'm using a docking station and it pulls juice from the docking connector), is there anything else I can do? I doubt that running two PSUs (one through the docking, one through the laptop) would improve the situation (Or would it? Is it safe?). I can supply schematics if needed.

 

One last push for the old fella?

 

Thank you!

[1610ftw]

Wow - way to go!

What 980m did you get for it?

 

If you can pull up to 213W from the wall I would strongly suggest to leave it at that.

 

This is a very old chassis by now and it can get pretty hot in places so 213W is probably the absolute maximum that HP was comfortable with when the 8740W was new so why not leave it at that? Also this is probably an EC limit like MSI is using and very hard to get around and there would be the risk of bricking your beautiful machine.

 

 

 

 

 

 

[triturbo]

1 hour ago, 1610ftw said:

What 980m did you get for it?

Clevo, 8GB, non G-Sync, Prema BIOS. Runs rock solid, but it is slower than the 1070, so I wanted to make it equal on the expense of power and heat. 
 

1 hour ago, 1610ftw said:

This is a very old chassis by now and it can get pretty hot in places so 213W is probably the absolute maximum that HP was comfortable with when the 8740W was new so why not leave it at that?

The system seems strong enough for something like 250~260W, the cooling is the one holding it back and I’m making a new, hopefully better one. 
 

1 hour ago, 1610ftw said:

Also this is probably an EC limit like MSI is using and very hard to get around and there would be the risk of bricking your beautiful machine.

Seems like it. Maybe I’ll leave it at that, if I can’t find more elegant solution than the wires to the MXM slot. 
 

[JadeRover]

 

Hi ! That's some epic modding, respect for keeping that old machine running under load !

 

15 hours ago, triturbo said:

I tried the Omen 350W (with custom made power plug) and the Slimq 330W with all 3 power plugs (two 330W and one 240W

 

What do you mean by that, you made a custom plug ? Is it a plug with resistors ? I think the max charger you can connect to HP workstations is 230W with a 100K resistor between VCC and ID pin.

 

16 hours ago, triturbo said:

The laptop has over current protection, but I thought that it would kick later/higher. So, the question is, other than running thick wires from the socket to the MXM slot (I don't want it since I'm using a docking station and it pulls juice from the docking connector), is there anything else I can do? I doubt that running two PSUs (one through the docking, one through the laptop) would improve the situation (Or would it? Is it safe?). I can supply schematics if needed.

 

You are bang on the money, what you need to do is find the power input shunt resistor that is used by the power management IC. You need to short it so that it's resistance is lower and the laptop will kick in the overcurrent protection for more than 217w load.

 

Running wires from the main power rail (tapping in on the motherboard and not on the barrel jack conector) to the MXM slot isn't a bad idea, it will take some of the load off of the internal power rails on the motherboard so it won't get as hot.

 

Not sure how two PSU's will help, just run your modified 350W (showing up as a 230w orignal HP ?) through the dockin conn.

 

For the shunt resistor, there might be one that is specific for the docking connector power input. One thing to consider is the docking conn is an array of pins and these might heat up under 10+ AMPS of load. If you feel like it heats up too much, use the barrel connector as it will have lower resistance and thus lower power loss.

 

I'll look up schematics for you HP, they should show which shunt resistor to short out.

 

Good luck !

[1610ftw]

2 hours ago, triturbo said:

Clevo, 8GB, non G-Sync, Prema BIOS. Runs rock solid, but it is slower than the 1070, so I wanted to make it equal on the expense of power and heat. 
 

The system seems strong enough for something like 250~260W, the cooling is the one holding it back and I’m making a new, hopefully better one. 
 

Seems like it. Maybe I’ll leave it at that, if I can’t find more elegant solution than the wires to the MXM slot. 
 

 

 

It is a shame the 1070 did not work out, it would have made things a lot easier!

 

My 8740W is with my youngest son right now and indeed the cooling is pretty bad, we have solved that for now with added cooling via external fan as otherwise temps ramp up too much and the external fan is also still pretty quiet. HP does not see to have planned this workstation with peak performance in mind.

 

If you go ahead with some kind of modding for higher power uptake then I hope you are right that the chassis is as robust as you estimate!

 

In any case it is a great combo - Dreamcolor 16:10, GTX980m and top of the line CPU!

 

 

[JadeRover]

3 hours ago, JadeRover said:

 

Hi ! That's some epic modding, respect for keeping that old machine running under load !

 

 

What do you mean by that, you made a custom plug ? Is it a plug with resistors ? I think the max charger you can connect to HP workstations is 230W with a 100K resistor between VCC and ID pin.

 

 

You are bang on the money, what you need to do is find the power input shunt resistor that is used by the power management IC. You need to short it so that it's resistance is lower and the laptop will kick in the overcurrent protection for more than 217w load.

 

Running wires from the main power rail (tapping in on the motherboard and not on the barrel jack conector) to the MXM slot isn't a bad idea, it will take some of the load off of the internal power rails on the motherboard so it won't get as hot.

 

Not sure how two PSU's will help, just run your modified 350W (showing up as a 230w orignal HP ?) through the dockin conn.

 

For the shunt resistor, there might be one that is specific for the docking connector power input. One thing to consider is the docking conn is an array of pins and these might heat up under 10+ AMPS of load. If you feel like it heats up too much, use the barrel connector as it will have lower resistance and thus lower power loss.

 

I'll look up schematics for you HP, they should show which shunt resistor to short out.

 

Good luck !

 

Found the schematic

 

So the DC jack and docking connector both have the same resistor that measure current meaning there is just one to short. Here it is :

(low res couldn't find a better pic)

 

It's the huge resistor near the battery conn and above the RAM, same side as the CPU.

[triturbo]

18 hours ago, JadeRover said:

What do you mean by that, you made a custom plug ? Is it a plug with resistors ? I think the max charger you can connect to HP workstations is 230W with a 100K resistor between VCC and ID pin.

 

Yes, the plug has resistor inside, otherwise the system refuses to recognize the Omen 350W. Also yes, 230W is the max stock PSU, which is not bad but both other options run a bit better and obviously have more room for experimentation.

 

18 hours ago, JadeRover said:

Running wires from the main power rail (tapping in on the motherboard and not on the barrel jack conector) to the MXM slot isn't a bad idea, it will take some of the load off of the internal power rails on the motherboard so it won't get as hot.

 

Sadly it's a long route around the motherboard and I'm not too keen on doing it.

 

18 hours ago, JadeRover said:

One thing to consider is the docking conn is an array of pins and these might heat up under 10+ AMPS of load. If you feel like it heats up too much, use the barrel connector as it will have lower resistance and thus lower power loss.

 

That's why I was wondering about two PSUs. Even though it's a thick trace/pin it's not a barrel connector. We'll have to see if I mod it successfully.

 

17 hours ago, 1610ftw said:

It is a shame the 1070 did not work out, it would have made things a lot easier!

 

Yeah, or the P5200 with the 16GB RAM, that would've carried out the system into another couple of years.

 

17 hours ago, 1610ftw said:

HP does not see to have planned this workstation with peak performance in mind.

 

It's just that the first gen i7 was HOT even compared to the QX9300. I think that's the reason 8760w/8770w received different cooler.

 

17 hours ago, 1610ftw said:

If you go ahead with some kind of modding for higher power uptake then I hope you are right that the chassis is as robust as you estimate!

 

We'll see 🙂

 

17 hours ago, 1610ftw said:

In any case it is a great combo - Dreamcolor 16:10, GTX980m and top of the line CPU!

 

Dream spec indeed, although seeing the return of 16:10 I'm dreaming about a new machine - that ZBook Fury G1i 18 is rather tempting, but the price is prohibitive for now.

 

14 hours ago, JadeRover said:

So the DC jack and docking connector both have the same resistor that measure current meaning there is just one to short.

 

MANY THANKS! That's a shunt modding, yes? Other than liquid metal, what should I put on it? Solder a thick wire, or a copper plate? First time doing it, so no idea what should I do.