HD4870 on PCI-E 1.1?

[Breznikov]

Hi all,

I saw another Topic where I saw and HD4850 could run in a PCI-E 1.1 slot without any bandwith problems. But what about a HD4870? That card uses quite a lot more bandwith, so will a 1.1 slot still be enough?

Also, I have a MSI P35-Neo2 FR motherboard with two PCI-E slots. In crossfire those will run at 16x and 4x speeds I believe (correct me if I'm wrong please). What if I would run a HD4850 in a 1.1 x4 slot (in Crossfire with another HD4850 or a HD4870)? Of course that will be a bottleneck for the card, but how much? Will it perform pathetically or will it give quite a bit extra performance?

I'm not planning on buying two cards now, but maybe I will buy another one in the future. But maybe it's better to buy a new motherboard if that time comes.

 

[the last resort]

The 4850 is unbelievably powerful. I just got one after getting rid of my 7600GT, and it is completely unbelievable. I am currently running it on a NVidia 570 SLI MCP chipset at PCI-E 1.1, and I haven't had seen any bandwidth issues.

 

[Breznikov]

I know it's powerful. It will be a huge difference with my X1950Pro which I'm using at the moment. But a Q9450 with 4GB of memory is a bit of a waste with a X1950Pro as my videocard, so I need to upgrade that fast

 

[Von_Matrices]

As far as using the HD4870 in a PCIe 1.1 x16 slot, it shouldn't make that much (<2%) of a difference compared to a PCIe 2.0 x16 slot. The card will be starved of bandwidth on very rare occasions making the upgrade to PCIe 2.0 x16 from PCIe 1.1 x16 not worthwhile.

As far as crossfired HD4850s, I have a similar system to you and have tried one of my HD4850s in the PCIe 1.1 x4 slot on my motherboard crossfired with an HD4850 in a PCIe 2.0 x16 slot. The results were pathetic compared to using the HD4850s in both PCIe x16 2.0 slots. Having 1/8 the bandwidth for one of the cards definitely chokes it of data and restricts its performance. I would definitely recommend an P45 w/ 2 x PCIe 2.0 x8 or X38/X48 w/ 2 x PCIe 2.0 x16 if you plan to crossfire.

Hope this helps.

 

[homerdog]

For a single 4870 a 16x 1.1 slot is fine. Crossfire on P35 is not recommended.

 

[Breznikov]

Thanks for the replies. I won't try Crossfire then on this mobo, I'll buy a new one when I think I need to. But for now, one card will be more then enough.

One last question about power consumption. I read somewhere that the HD4850 requires 30A and the HD4870 36A. My PSU supplies 14A on the 12V1 line and 15A on the 12V2 line, so 29A in total. That is just one Amp short to run the HD4850, but will that really make any difference for the HD4850? If I get a '70, I definately need a new PSU, but can anyone tell me if I really need a new one with just one amp short?

My PSU is a Coolermaster eXtreme Power 430W.

 

[nukemaster]

It is important to know that a PSU's total 12 volt power is not always found by adding all the rails.

For example a OCZ GameXtreme 700 has 4 18 amp rails, but the total max is still only 50(600 watts) amps not 72. 72 amps at 12 watts would be 864, quite a feat for a 700 watt psu

Most multi rail systems are to meet the ATX specs. They state that NO rail should take more then 20 amps(correct me if this is the wrong number someone). This said your total power MAY be that but may be lower.

New power supplies can send almost all of there power to the 12 volt rails. A new 450 watt psu can most times deliver 400+ watts on its 12 volt rails, where as an older one will deliver less.

Efficiency is another factor, your current PSU lists 70%(i assume at half load as that is the most efficient zone on almost all PSU's). Getting a new PSU is a good idea to save power and have some extra head room.

Now that you are boarded, the Video card does not take 30 amps. 30 amps is for a FULL system with the card. If the card took 30 amps it would be consuming 360 watts. Your cards power is about 110 watts(9.166666666666666666666666666666666666666666666666666666666667 amps) at full load.

The rest of your system will determine how much power you need.

 

[Breznikov]

Thank you very much for your reply, I'm learning quite a bit here

Rest of my system:
Intel Core 2 Quad Q9450 @ Stock (might overclock that later, so I need a bit of 'headroom' to do that)
OCZ PC8000 4GB (2x2GB)
MSI P35 Neo2-FR
Sapphire ATi Radeon X1950 Pro, which will be changed, as I said.
DVD-writer

I know a thing or two about hardware, but I'm quite a newb to power consumption, so any help will be appreciated.

OCZ PSU's are quite cheap, but are they any good? I have heard a few negative things about them, like being quite noisy. I don't want to spend TOO much on a new PSU, so I am interested in the OCZ's, but if they aren't that good I'll look for a Coolermaster or a Corsair.

 

[nukemaster]

Well a quick look at your psu shows the total 12 volts at 29 amps, its cutting it close, but should run if the psu holds to its specs.

 

[Breznikov]

Thank you.

I think I'll just try it with my current PSU. If it doesn't work, I'll get a new one at the local PC Store.

 

[nukemaster]

keep a good eye on it.

I am still running a 8800GTX E6600 2 HDD system with a 450 watt psu.