Saturday, July 19, 2008

Unleashing the 4850 Part 3 - Cooling and overclocking

Finally i will finish off my little HD4850 adventure. I was quick to wrap this up because i picked up some new hardware today and just couldn't wait to play.

Here's the naked card. We will need to add a heatsink to the mosfets on the right which is very important because these suckers get hot.

Here's the heatsink in question. I found it in the deep dark depths of my cupboard o' crap. I think it was an old P3 heatsink (half of one anyway).

Here's a shot of the bottom. The small step makes it a perfect fit for the card!

I installed it using thermal tape but due to its weight, i used a cable tie to ensure it doesn't fall off.

I had every intention of adding ramsinks, but unfortunately i didn't have any on hand that were suitable. The best ramsinks (imho) are made by chopping up any old gpu/cpu/nb/sb heatsinks and sticking them on with artic adhesive or thermal tape. Spending $30 for a pack of 8 pre made ramsinks is crazy. I know i can think of hundreds of better things to spend that on. Do not overvolt the ram without ram sinks. The ram gets very hot to touch even at stock settings, i do recommend overvolting with ramsinks and decent airflow.

I'll be using a Swiftech MCW60 waterblock to cool the gpu on this beast. Many prefer the option of the full cover waterblocks but nothing can match the simplicity and upgradability of the MCW60. I could argue all day why the full cover blocks are a waste of money... but i wont. Lets just get into some overclocking!

Unfotunately nearly all the pictures i took did not turn out. Photography isn't my strongest asset and most shots were taken over by the flash reflection. Here's one shot of the card in my rig with the waterblock installed. One thing to note is how simple reading the voltages becomes with the use of the molex connector. The test probe slots right in and there's no danger of shorting any components. As you can see, the VGPU mod is turned on (bottom) and the VDDR is in the off position.

The test setup:
E8400 @ 4ghz - Frozen SS
Gigabyte x48-DS4
Corsair 2x2gb PC2-8400 Dominators
Connect3D HD4850 - MCW60
74gb WD Raptor
Thermaltake 750watt Toughpower
Fluke Multimeter :)

I used 3DMark Vantage to test for max stable clocks without artifacts. Note that i only overclocked the memory to an even 1000mhz (stock 993mhz). This was due to not having any ramsinks installed and i didn't want to take the risk of damage.

Stock cooling and voltage (1.2v load) i only managed a pathetic 670mhz on the core. Any higher than this and i would get slight graphic corruption and experience crashing. Temps were well above 90 degrees load.

With a voltage bump (1.3v load) i was able to achieve a very respectable 890mhz on the core. I was very happy with this result for safe 24/7 gaming. Temperatures only hit around 43 degrees load which says excellent things about the MCW60.

I finally bumped the voltage again up to 1.4v (still, fairly safe under water) and managed an amazing run of Vantage at 975mhz on the core. This was not stable for 24/7 use however, but with a little extra voltage i'm sure i could have broken 1 ghz on the gpu.

Overall i'm extremely impressed with the 4850s performance and it's excellent response to voltage. Priced at only $200, these cards deliver exceptional results and are unmatchable in their price bracket. I would highly recommend voltmods for this card if you're after maximum performance and are keen to take the plunge into extreme overclocking territory.

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