Doing something stupid today...

[Spikkel]

OK, so here is the plan: 

I have some really old PC parts and want to build a guest gaming-PC. I don't want to spend any additional money on it, but the components are not a 100% compatible...

Here is the problem: I have a 300W power supply, (a have a spare if i need to install both ~ that will be fun) and a MSI Radeon HD 3870 graphics card. The card needs a 6-pin power connector which neither of the PSUs have.

Now I know that 300W is on the low side for a HD3870, and the absence of a 6-pin connector is generally a bad sign, but hey lets see what happens...

I have a 2x Molex to 8 pin adapter, think it might be for the CPU power because the pins doesn't fit into the card. I made them fit.... ~ no surprise, the PC doesn't boot. It does if I take the card out.

 

So here is my question, I most probably have to install the second PSU, with all the drama that comes with that, but I'm now also unsure about the wiring of my adapter. I don't quite get the pin-out diagrams. Do I need a "sense wire" and where does it go? I have 4x black wires on top (the side of the retaining clip) and 4x yellow at the bottom. The first two sets of wires goes to the first molex with blacks on the inside and yellow on the outside. And the last 2 pairs goes to the second molex. Is this correct?

[NelizMastr]

The 8-pin EPS (or Dual 4-pin P4) isn't electrically compatible with PCIe, so don't even bother. You'll need a dual molex to 6-pin adapter. Be glad nothing blew up.

[paddy-stone]

Yes, it is entirely stupid to do that.

[doomsriker]

23 minutes ago, Spikkel said:

have a 2x Molex to 8 pin adapter, think it might be for the CPU power because the pins doesn't fit into the card. I made them fit.... ~ no surprise, the PC doesn't boot. It does if I take the card out.

 

[doomsriker]

29 minutes ago, Spikkel said:

OK, so here is the plan: 

I have some really old PC parts and want to build a guest gaming-PC. I don't want to spend any additional money on it, but the components are not a 100% compatible...

Here is the problem: I have a 300W power supply, (a have a spare if i need to install both ~ that will be fun) and a MSI Radeon HD 3870 graphics card. The card needs a 6-pin power connector which neither of the PSUs have.

Now I know that 300W is on the low side for a HD3870, and the absence of a 6-pin connector is generally a bad sign, but hey lets see what happens...

I have a 2x Molex to 8 pin adapter, think it might be for the CPU power because the pins doesn't fit into the card. I made them fit.... ~ no surprise, the PC doesn't boot. It does if I take the card out.

 

So here is my question, I most probably have to install the second PSU, with all the drama that comes with that, but I'm now also unsure about the wiring of my adapter. I don't quite get the pin-out diagrams. Do I need a "sense wire" and where does it go? I have 4x black wires on top (the side of the retaining clip) and 4x yellow at the bottom. The first two sets of wires goes to the first molex with blacks on the inside and yellow on the outside. And the last 2 pairs goes to the second molex. Is this correct?

Buy this. It will give you similar performance to that 3870 and is passively powered (No external connector needed). I know you don't want to spend anything, but this will be well worth the 20$ investment. Not to mention it has DX11 support.

 

https://www.ebay.com/itm/Dell-AMD-Radeon-HD7570-1GB-128-Bit-GDDR5-PCI-E-Low-Profile-Video-Card-KFWWP/273047164780?hash=item3f92e1176c:g:wrwAAOSwXsFacBAH

[ProjectBox153]

3 minutes ago, doomsriker said:

Buy this. It will give you similar performance to that 3870 and is passively powered (No external connector needed). I know you don't want to spend anything, but this will be well worth the 20$ investment. Not to mention it has DX11 support.

 

https://www.ebay.com/itm/Dell-AMD-Radeon-HD7570-1GB-128-Bit-GDDR5-PCI-E-Low-Profile-Video-Card-KFWWP/273047164780?hash=item3f92e1176c:g:wrwAAOSwXsFacBAH

That’s a low profile card, so it wouldn’t fit right unless OP is using a LP case. 

[doomsriker]

Just now, Jamiec1130 said:

That’s a low profile card, so it wouldn’t fit right unless OP is using a LP case. 

I figured he wouldn't mind disconnecting the bracket and zip tieing or letting it hang considering he tried to jam a CPU power lean into a GPU....  

[Spikkel]

40 minutes ago, NelizMastr said:

The 8-pin EPS (or Dual 4-pin P4) isn't electrically compatible with PCIe, so don't even bother. You'll need a dual molex to 6-pin adapter. Be glad nothing blew up.

What is the difference between the two? I want to try and modify it.

[Spikkel]

5 minutes ago, doomsriker said:

I figured he wouldn't mind disconnecting the bracket and zip tieing or letting it hang considering he tried to jam a CPU power lean into a GPU....  

LOL!!! Well yes, a little less brutish.. I used a small razor blade to shave the square pins round.

[Spikkel]

34 minutes ago, paddy-stone said:

Yes, it is entirely stupid to do that.

Stupid but fun. And hey, it's the best way to learn new skills. The hardware is wasted anyway if I can't get it working this way.

[doomsriker]

9 minutes ago, Spikkel said:

I want to try and modify it.

No you don't trust me. Most PSUs that omit pcie power connectors do so for a reason. If this were a 750ti you could use a sata power to 6 pin for the extra 5 watts, but this card will be asking for a good deal more than 5 watts from that 6 pin. 

[Spikkel]

21 minutes ago, doomsriker said:

Buy this. It will give you similar performance to that 3870 and is passively powered (No external connector needed). I know you don't want to spend anything, but this will be well worth the 20$ investment. Not to mention it has DX11 support.

 

https://www.ebay.com/itm/Dell-AMD-Radeon-HD7570-1GB-128-Bit-GDDR5-PCI-E-Low-Profile-Video-Card-KFWWP/273047164780?hash=item3f92e1176c:g:wrwAAOSwXsFacBAH

"Shipping: May not ship to South Africa"

We don't really have a good second hand market in South Africa. The cheapest NEW card I could find that would match the HD3870 is the same price as a new power supply

[Spikkel]

27 minutes ago, doomsriker said:

No you don't trust me. Most PSUs that omit pcie power connectors do so for a reason. If this were a 750ti you could use a sata power to 6 pin for the extra 5 watts, but this card will be asking for a good deal more than 5 watts from that 6 pin. 

Remember, the GPU will be powered by its own dedicated PSU. If I'm correct, a molex provides 8.5 Amps at 12V. With two of them its just over 200 watts. Should be fine...?

[Spikkel]

1 hour ago, Spikkel said:

What is the difference between the two? I want to try and modify it.

I found the correct wiring diagram:

 

[Spikkel]

IT WORKS!!! I'm typing this from the machine in question. Wel... I still have to do a stress test, but I'm too scared, probably first have to install the second PSU... Naaahh lets try. If you don't hear from me in two days my house burned down...

[Spikkel]

It survived the "Fuzzy donut of death" AKA Furmark, running prime95 in die background to put full load on the PSU. I really didn't think this would work.

EDIT: Stil only runs from the single 300W PSU with no native 6-pin power connector.

 

BIG DISCLAIMER: I was willing to lose some hardware to try this. I could have lost any of the components in my system ~ so only try this if you are willing to take the same kind of risk. There was also an electrocution and fire hazard.

[paddy-stone]

10 hours ago, Spikkel said:

Stupid but fun. And hey, it's the best way to learn new skills. The hardware is wasted anyway if I can't get it working this way.

It'd be easier and much less stupid to just buy an adaptor lead for like $2 or less possibly, some cards come with the damn things in the box, but they are usually very cheap on Amazon and ebay.

[Spikkel]

8 hours ago, paddy-stone said:

It'd be easier and much less stupid to just buy an adaptor lead for like $2 or less possibly, some cards come with the damn things in the box, but they are usually very cheap on Amazon and ebay.

This is Africa... The shops doesn't stock everything (I've been to all the local stores) and Amazon delivery fees are too high to ship to RSA. Ebay don't even ship to RSA. But hey, the idea was to try something stupid and.. it worked. I had fun doing it and now I have a extra working system.

[paddy-stone]

4 hours ago, Spikkel said:

This is Africa... The shops doesn't stock everything (I've been to all the local stores) and Amazon delivery fees are too high to ship to RSA. Ebay don't even ship to RSA. But hey, the idea was to try something stupid and.. it worked. I had fun doing it and now I have a extra working system.

Well, I'm sure someone would've sent you one if you'd asked... I myself have several that aren't being used. If things are so hard to come by there, then why risk ruining it.. I don't see the logic there at all.

It's your hardware and you're welcome to do whatever you want with it, I just personally wouldn't risk it if things are so hard to come by.