Is this safe?

[Fate]

So my power supply is a CX430M, and only has 32a on the 12v rail (384w). I want to buy a cheap 7870 to pair with my R9 270 to hold me over until new cards come out, however, my power supply likely isn't powerful enough. I do however have an old OEM PSU that has worked great over the years in a HP A6112n before it was retired. It has 14a on the 12v rail (168w) which is more than enough to power a 7870, but, I have no idea how safe that would be until I can get a new PSU. I already tried to see if it would work by shorting the 20 pin connector and the PC/GPU booted just fine, but again, I'm not sure how safe it is. Has anybody tried it? Would it be plausible?

2GB vram isn't really a limitation for me atm because the games I play aren't bottlenecked by it at 4k as long as I have AA turned down (past 4-8x my fps goes from the 40-70s to 3-4), and I'm fine with turning it down to 1440p when/if needed.

 

[WoodenMarker]

It could work but I would just hold off until you get a new psu. 

[IdeaStormer]

I wouldn't do it. If you do you need to make sure both power supplies use the same exact ground or you'll fry something, then using those molex converter to 4 or 6 pin power for PCIe is meant for a temporary fix, long term = bad news, I shy away from such converters best to use the power connector for the intended purpose not sure how those converters get approved when they only lead to problems.

[d33g33]

You can get devices or wire into the start wire to ensure that both PSU's start at exactly the same time. This is what you need to do this 'safely' but its not ideal.

 

For the cost and investment in new cards in the future it might be worth upgrading your PSU now?

[Fate]

It could work but I would just hold off until you get a new psu. 

 

I wouldn't do it. If you do you need to make sure both power supplies use the same exact ground or you'll fry something, then using those molex converter to 4 or 6 pin power for PCIe is meant for a temporary fix, long term = bad news, I shy away from such converters best to use the power connector for the intended purpose not sure how those converters get approved when they only lead to problems.

 

You can get devices or wire into the start wire to ensure that both PSU's start at exactly the same time. This is what you need to do this 'safely' but its not ideal.

 

For the cost and investment in new cards in the future it might be worth upgrading your PSU now?

Okay, I'll look into buying a new PSU before doing anything.

I'll probably just sell my R9 270 then and I'll only need about $100 to get something like a 290. 

 

Can someone recommend a PSU for about ~$60-70 that can potentially power two 290's? I was thinking a 750 G2.

[IdeaStormer]

Okay, I'll look into buying a new PSU before doing anything.

I'll probably just sell my R9 270 then and I'll only need about $100 to get something like a 290. 

 

Can someone recommend a PSU for about ~$60-70 that can potentially power two 290's? I was thinking a 750 G2.

 

For two 290's I hope you spend a bit more and get something quality, I'm not sure 750 W will do you with two 290's. Better ask someone with such a setup, but I bet they use 850 W or more.

[Fate]

For two 290's I hope you spend a bit more and get something quality, I'm not sure 750 W will do you with two 290's. Better ask someone with such a setup, but I bet they use 850 W or more.

Anandtech says two 290x's are 651 watts under load, granted that's not on uber mode and is probably reference design.

[Faceman]

Okay, I'll look into buying a new PSU before doing anything.

I'll probably just sell my R9 270 then and I'll only need about $100 to get something like a 290. 

 

Can someone recommend a PSU for about ~$60-70 that can potentially power two 290's? I was thinking a 750 G2.

A 750G2 is going to cost $70 if you catch it on a good sale.  Usually costs $90+

 

The EVGA 750 B2 is on sale for $50 right now if I'm not mistaken.  Its the same PSU, except Bronze instead of gold.  Johnny Guru gave it a 9/10

[quan289]

There's a lot of low-end power supplies that requires a certain load ratio between the +12v and the 3.3/5v rails. In your case, you are putting zero load on the 3.3/5v rail and a higher 12v load. This would cause the voltage of the 12v to severely drop while the other rail increase. You can see this in action during crossload testing on PSUs at Jonnyguru, Techpowerup, etc.

 

Can someone recommend a PSU for about ~$60-70 that can potentially power two 290's? I was thinking a 750 G2.

 

The EVGA Supernova 750w B2 is a good option in that price point if you don't mind rebates.

[quan289]

Its the same PSU, except Bronze instead of gold.

 

Same manufacturer (Super Flower); different platform (Golden Green vs Leadex)

 

The B2 is a solid unit nonetheless.

 

Edit: Yes, you are correct, you could get the B2 for $50 after MIR at NCIXUS - making it the best value unit in that price range: https://pcpartpicker.com/part/evga-power-supply-110b20750vr

[Fate]

A 750G2 is going to cost $70 if you catch it on a good sale.  Usually costs $90+

 

The EVGA 750 B2 is on sale for $50 right now if I'm not mistaken.  Its the same PSU, except Bronze instead of gold.  Johnny Guru gave it a 9/10

 

Same manufacturer (Super Flower); different platform (Golden Green vs Leadex)

 

The B2 is a solid unit nonetheless.

Alright I'll look into the B2, seems really good at a first glance. 

Thanks

[quan289]

Alright I'll look into the B2, seems really good at a first glance. 

Thanks

 

You're welcome. In case you didn't see my edit, as Faceman said, you could get the B2 for $49.99 after MIR at NCIXUS: https://pcpartpicker.com/part/evga-power-supply-110b20750vr

 

Here's a review on it: http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=393