PC not powering up after upgrade to Radeon 4890

[tdbmoss]

Hi all, hope you can help me with this, apologies if it’s a dumb question…

So I’ve got a Sapphire Radeon HD 4890 Vapor-X 2GB graphics card to upgrade from a Radeon 3850 512 MB, but my problem is that when I install this card the machine will not start up at all – the case lights just flash on and off for a split second when trying to power up and apart from that it’s as if it's totally dead – if I swap back to the 3850 it works fine again though.

I’m thinking it might be some kind of power issue, but I’m not really that familiar with all the PSU-related jargon etc – the PSU has one 6-pin PCI Express power connector on it, which is used to power the 3850 fine. The 4890 also requires an 8-pin PCI-E connector though, so I got an adapter that turns two standard “molex” connectors into one PCI Express 8-pin one, and connected both the built-in 6-pin and the 8-pin (via adapter) to the 4890 (I just connected the adapter to any two “molex” connectors, I am assuming they are all equal and it doesn’t matter which ones are used).

The box for the 4890 says it requires at least a 500W PSU, and mine is a 650W one, three years old. The rest of the machine is a Core i5 661 3.33 GHz, 4 GB DDR3 Ram, 2x hard drives, 1x DVD drive, separate sound card, some lights etc.

The thing I don’t get so much is the amp requirements – I read elsewhere that a typical 4890 needs “65W / 270W .. 5.4A / 22.5A” (idle/load) – the wattage doesn’t sound a problem as I have 650W total, I don’t really understand the amps or how to know if I have enough – the table on the sticker on the PSU is as follows, if this makes any sense:

+3.3v, +5v, +12v DC1, +12v DC2, -12v, -5v, +5VSB
30A, 30A, 14A, 15A, 0.5A, 0.8A, 2.5A

So I’m kinda at a loss what to do now – I don’t mind replacing the PSU but don’t want to spend the money and then find that I still have this problem – if you think that a new PSU would solve this problem what is the cheapest one from this site – http://www.ebuyer.com/search?sort=pr...imit=10&page=1 (starting from the cheapest) – that would run the 4890 happily, preferably one that has two PCI-E connectors built-in as then I guess you know that it is more designed for this kind of thing? http://www.ebuyer.com/product/176439 has the right connectors and is 600 W so in theory would run the 4890, but is this any good, and if it is why does my current 650 W one not seem to like it? :S Alternatively it seems you can spend a lot of money eg http://www.ebuyer.com/product/200491 - is it worth it though over the cheaper ones, is it more likely to work with the 4890? I'm sure my current one was half that price for the same total wattage...

Thanks in advance!

[Whir]

The 4890 also requires an 8-pin PCI-E connector though, so I got an adapter that turns two standard “molex” connectors into one PCI Express 8-pin one, and connected both the built-in 6-pin and the 8-pin (via adapter) to the 4890 (I just connected the adapter to any two “molex” connectors, I am assuming they are all equal and it doesn’t matter which ones are used).

Try connecting the 8-pin adapter into two separate leads, not just two molexes on the same lead.

If not, try using a different PCIe16x slot on the motherboard for the card. It sounds like Voodoo, but one of my motherboards (an older DFI) wouldn't let my ATi cards work in the #1 slot, only nVidias.