Enermax Liberty 620W enough for two 4870 (1GB)?

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Khaydarin

2[H]4U
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Dec 13, 2005
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I have an Enermax Liberty 620W power supply, and I have no doubt that it will be able to hand the 4870 1GB card that I just got. The rest of my system is:

- Gigabyte EP45-UD3P
- 2 x 2GB 1066 RAM
- E8500
- Extreme Music X-Fi soundcard
- 4 x 120mm fans (3 case, 1 for the CPU)
- 80 GB HDD (IDE)...regularly used; has my OS and main programs on it.
- 2 x 750 GB HDD (SATA)....less commonly used; stores games, music, and movies.
- 1 DVD Burner

My question is, would I be safe in hooking up a second 4870 for Crossfire with this PSU?

The 4870 requires two 6-pin PCI-E connectors to run. Since my PSU only has two dedicated PCI-E connectors, they would both got into the first 4870. However, the 4870 came with adapters to turn two molex connectors into two 6-pin connectors. To power the second card, I would use those adapters. Is this unsafe? Will I have enough power to do this?

I'm just trying to save myself the cost of paying for a brand new PSU if I don't need one.
 
i would say go for it... it might be pretty close to the power supply's recommended 80% max load continuously but especially that being an enermax supply i think youll be fine
 
I say no. It's cutting it waay too close.

Let's see a single HD4870 uses up 150W of power at full load. So two would take up 300W of power by themselves. There's only 432W or 36A on the +12V rail of that PSU. So there would only be about 132W of power left on the +12V rail after the video cards are taken care of. Considering that three hard drives will take up around 15W to 25W at boot up, that's another 45W to 75W of power being used, Using the worst case scenario, that's only 57W of power on the +12V rail for just CPU, mobo and fans. Using the best scenario, that's only 87W of power on the +12V for just the CPU, mobo, and fan. And we haven't factored in any sort of CPU overclocking you might do. So you would be stressing that PSU since you're putting 100% load on the +12V rail and don't have enough power for all the parts.

You would have no headroom at all with that PSU and HD4870 Crossfire. I recommend getting a new PSU with at least 40A on the +12V rail, though go for 50A on the +12V rail if you can.
 
Danny Bui said:
I say no. It's cutting it waay too close.

Let's see a single HD4870 uses up 150W of power at full load. So two would take up 300W of power by themselves. There's only 432W or 36A on the +12V rail of that PSU. So there would only be about 132W of power left on the +12V rail after the video cards are taken care of. Considering that three hard drives will take up around 15W to 25W at boot up, that's another 45W to 75W of power being used, Using the worst case scenario, that's only 57W of power on the +12V rail for just CPU, mobo and fans. Using the best scenario, that's only 87W of power on the +12V for just the CPU, mobo, and fan. And we haven't factored in any sort of CPU overclocking you might do. So you would be stressing that PSU since you're putting 100% load on the +12V rail and don't have enough power for all the parts.

You would have no headroom at all with that PSU and HD4870 Crossfire. I recommend getting a new PSU with at least 40A on the +12V rail, though go for 50A on the +12V rail if you can.
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Thanks for the info. I'll wait to buy the second 4870 until I have enough money for a solid new PSU. What PSU do you think would be a good replacement? Brand, wattage? How about something around 800-850W?
JBrinley said:
why do you have a IDE boot drive?:confused:
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I had one of the 1.5TB Barracuda's from Seagate, however it died the afternoon after I build my brand new (and current) PC. I had already installed Vista, drivers, and all my "standard" programs. Very frustrating. The only extra HDD that I had on hand was a lowly 80GB IDE drive. So I threw that in there and waited for Seagate to send me a new 1.5TB drive. Long story short, three of those 1.5TB drives died in my PC so they just sent me two 750's so I don't have to deal with that particular 1.5TB model anymore. Those larger drives are mainly for storage of things like ripped DVD's, music, and games. The 80GB has chugged faithfully on the entire time....and to be honest I really have no problem with it's speed; I can't tell whether its slow or not.
 
Khaydarin said:
Thanks for the info. I'll wait to buy the second 4870 until I have enough money for a solid new PSU. What PSU do you think would be a good replacement? Brand, wattage? How about something around 800-850W?
Click to expand...

Right now, this is a good deal for a quality 750W PSU with 60A on the +12V rail sold by a quality manufacturer:
PC Power & Cooling S75CF 750W PSU - $110

But basically stick to known brands such as Corsair, Seasonic, PC P&C, Antec, BFG, or Silverstone. Make sure that the PSU has 50A on the +12V rail.
 
I have a system that uses the Liberty 620, and it got flakey with dual 7800GT's. Of course, this one is a replacement. The Liberty series just didn't have the same reliability the older lines had. Luckily, with only a single card and a bunch of HDD's, the thing is near perfect, and silent.
 
my 8800gts SLI ran just fine with a 600 500watt coolermaster for a year shouldnt have a problem at all
 
dengar said:
my 8800gts SLI ran just fine with a 600 500watt coolermaster for a year shouldnt have a problem at all
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Two 4870s use significantly more power than two 8800GTS cards, not to mention the OP has 3 HDs as well. I agree with Danny's assessment considering the 620W Liberty's 12V rail is a bit anemic compared to more recent quality PSUs.
 
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