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Overclocking the Radeon HD 5850

Overclocking the Radeon HD 5850

We’ve had a fair amount of time to play with the Radeon HD 5850 now, and let us begin by saying that this card packs a serious punch. Even at its factory defaults, the 5850 offers significant performance, but it’s capable of so much more. To that end, follow along as we show you how to squeeze up to 25% additional performance out of your HD 5850.

As with all jobs, we need to begin by gathering the correct tools. While we can make a certain amount of progress with the Overdrive feature of the Catalyst Control Center, the imposed limits are nowhere near what the card is actually capable of achieving. To get around this problem, we’re going to need some extra programs.


Test setup


Memory overclocking

The first thing you’ll want to do is determine the quality of the RAM on your 5850. This can be a slightly tedious process, but it is worth doing this first, because the 5850’s core clocks do not affect RAM stability. Therefore, whatever maximum stable setting your RAM achieves can be used later while experimenting with core clocks.

To begin, fire up Furmark and begin a stability test in a 1024×768 window; it doesn’t matter if other applications are placed on top, but make sure that it is not minimized. Give Furmark a couple of minutes to get the card warmed up, and then open the AMD GPU Clock Tool. The stock VRAM speed on the 5850 is 1000MHz, and that is the setting you should see to begin with.


Most 5850s are capable of exceeding the overdrive limit set in the Catalyst drivers, so we suggest setting your memory clock to 1150MHz as your starting point. After you apply the setting, bring the Furmark window to the foreground, and allow the test to run uninterrupted for about 15 minutes. If at the end of 15 minutes the PC has not rebooted and the graphics driver has not thrown a VPU recovery, begin a process of gradually increasing the memory clock by 5-10MHz and testing after every increase.

If the driver undergoes a VPU recovery or the PC restarts, you have discovered the point at which the memory on your graphics card is unstable. Reduce the memory clock by 10MHz, and allow Furmark to test the setting for at least three hours. We recommend this test be run for at least six hours if you believe you have determined your final memory clock.

If the test fails after an extended period of time, reduce the memory clock by another 10MHz and re-run the stability test. At this point, your memory clock should be stable. Our Gigabyte HD 5850 demonstrated a maximum stable memory setting of 1175MHz.

Testing the VRAM overclock with Furmark.

Testing the VRAM overclock with Furmark.

Core overclocking

To begin overclocking the core, proceed as you did when you began testing memory clocks; fire up an instance of Furmark in 1024×768 window and allow it to warm the GPU. After several minutes, open the AMD GPU Clock Tool and reset your VRAM speed to final frequency determined in the previous section.

With the memory clock set, you can begin overclocking the GPU core. Start with a core frequency of 775MHz and let Furmark continue to run; during this time, it is a good idea to watch Furmark closely. If your core clock is too high, you will begin to see artifacts in Furmark’s rendering.

When Furmark artifacts appear, reduce the core clockspeed by 5-10MHz and continue testing. Even if you reduce the core clock, there is a chance that the 5850 may not stop producing artifacts until the driver resets the card. If this happens, simply close the benchmark and wait for the graphics driver to perform a VPU recovery.

A Catalyst VPU recovery takes about 10 to 15 seconds, during which time you will likely either have a blank or very garbled screen. This is normal, and you shouldn’t worry about it. Once the recovery has ended, decrease the core clock by 5-10MHz and resume testing with Furmark.

If, however, the card seems to be stable with a core clock 775MHz, begin increasing it in 5MHz increments. Keep a close eye on Furmark and watch for the first increase that produces visible artifacts. When you begin to notice artifacts in Furmark, immediately close the program and reduce your core clock speed by 10MHz. This frequency could be the final stable overclock.

To find out if the overclock is indeed stable, we suggest running Unigine Heaven in full-screen mode. Be aware that the Catalyst driver’s VPU recovery mechanism may continue resetting your card’s frequency during this time, even though your core is stable. To correct this problem if it occurs, set your 5850’s core clockspeed to 725MHz, run Furmark’s stability test for a few moments, and then set the core back to your current overclock.

We found that Unigine was much more likely to expose stability issues with the 5850’s core than Furmark, so you may still need to perform further adjustments of the GPU clock. However, if the Heaven demo runs for several hours without issue, you have found your maximum core speed without over-volting the card. Those who are concerned about the lifespan of their GPU may wish to stop at this point.

Testing the 5850 overclock with no voltage changes.

Testing the 5850 overclock with no voltage changes.


Disclaimer: Increasing the voltage of your 5850 carries the risk of permanently damaging your video card. Though we would not suggest settings we ourselves have not run, continuing with this guide acknowledges you are aware of the risks. Icrontic is not responsible for your damaged hardware!

Our 5850’s core was stable at 800MHz without any extra juice, but the 5850 is capable of more with a bump in voltage. During this process, you will use the MSI Afterburner tool to control the core voltage and fan speed of your 5850, and AMD GPU Clock Tool to set the clock speeds.

Please note that the AMD clock tool will reset the 5850’s fan speeds when it applies new settings, so you will need to reconfigure the fan’s RPMs in Afterburner whenever you change your clock speeds in the AMD tool.

Since both the 5850 and the 5870 use the same physical core, we felt a good starting point for our 5850 was the 5870’s stock Vcore of 1.15V. To do this, open MSI Afterburner, click on the number next to the Core Voltage (mV) slider and enter 1150, then click apply.

Proceed again with the core overclocking process we outlined in the previous section. Move upwards by 5-10MHz at a time, and keep a close eye on Furmark for artifacts. Terminate Furmark and reduce the core’s clock speed by 10MHz when artifacts appear, and then run Unigine Heaven for several hours.

If all goes well, and you do not experience any VPU recoveries, you have found your card’s stable frequency at the 5870’s stock voltage. Our HD5850 was stable up to 875MHz using 1.15V.

It is possible to gain further performance from the 5850, but this requires adjustment of the GPU’s fan speeds. Fortunately, this is something MSI Afterburner lets us do very easily.

You can set the fan speed to a fixed level at the main screen, but you can also customize Afterburner to control the fan speed according to its own included temperature chart. To do this, click the settings button, and then open the fan tab. Tick the “Enable user defined software automatic fan control” box, and then set the graph to your liking.


We used a maximum setting of 56% at 86°C, as this figure strikes a good balance between noise and performance.

Once you have configured your manual fan speed settings, you’re ready to try for another increase in your core clock speed. Gradually increase the core clock speed in 5MHz increments, and keep an eye on Furmark for artifacts. If you see any, give your 5850 a little bit of extra voltage not to exceed 1.25V.

During this process, it is important that you keep an eye on the temperature of your 5850. Furmark shows your card’s current temperature, and MSI Afterburner’s hardware monitor also has a graph for GPU temperature. We strongly suggest that you do not allow your 5850 to run above 85°C for an extended period of time.

If the card cannot be brought under 85C at a fan volume that’s comfortable for you, back down the card’s core clock until the temperature is under control. Once that is done, set the Heaven benchmark up for an extended run to verify stability. If the PC does not crash or the Catalyst drivers do not undergo VPU recovery, you’ve discovered your final clockspeed.

Our HD5850’s core produced a maximum stable speed of 925MHz using 1.225V. At this setting, the fan needed to be run at 65% duty cycle to keep the card below 85°C. While noisy, we found that the setting was reasonable enough for gaming use.

Testing with Furmark at 1.225V.

Testing with Furmark at 1.225V.

BIOS modding

Warning: This section is for advanced users only. Modifying or changing the BIOS of your HD5850 may result in an unusable or “bricked” card. We do not recommend attempting a BIOS mod unless you own a separate graphics card and your PC has two x16 slots, or your PC has onboard video that can be activated while a discrete card is present. Any BIOS modifications you implement are done at your own risk.

Overclocking the 5850 can squeeze considerable extra performance from the card, but the need for two programs to handle overclocking is pretty clumsy. Thankfully, flashing a new BIOS will allow you to control the card entirely from the MSI Afterburner application.

In order to flash your 5850’s BIOS, you’re going to need a way to boot into true DOS (a bootable floppy or flash drive) and the ATI BIOS flash tool. If you want to make any changes to the BIOS you’re going to flash, you will also need the Radeon BIOS Editor. Lastly, you’ll need the modified MSI BIOS which sets the overdrive limits to 1500 core/2250 memory.

You may have noticed that we used an MSI BIOS on our Gigabyte card. This is because the first generation of Radeon 5000 series products were produced exclusively by AMD, and later rebranded by various vendors like Sapphire, XFX and Gigabyte. This means that all boards, regardless of the brand, are compatible with same BIOS.

How to flash

  1. Save the new BIOS file and the atiflash executable on your DOS boot media.
  2. Restart your PC and boot into DOS mode.
  3. Back up your original BIOS by issuing the following command: atiflash.exe -s default.rom
    • Note: It would be a good idea to copy this BIOS file to another location. Backups are important.
  4. Flash the 5850’s BIOS with the following command: atiflash.exe -fs -p yournewbios.rom
    • Replace yournewbios.rom with the file name of the BIOS you downloaded. If you did not change the name of the file, it will be “MSI_R5~1.A11.”
  5. Reboot back into Windows once the flashing process has completed.

If the new BIOS was flashed successfully, you can now control the clock speed of your card within MSI Afterburner. We ended up making heavy use of Afterburner for its ability to save and recall overclocking profiles in one click.


We benchmarked our 5850 at all the speeds and voltages we suggested throughout this article. For reference, we compared the 5850 to a BFG GeForce GTX 285 OC at both stock and maximum stable overclocked frequencies.

For reference, the benchmarks refer to the following voltage/frequency settings:

  • HD 5850 (Stock) = 725MHz Core / 1000MHz RAM
  • HD 5850 (OC) = 800MHz Core / 1175MHz RAM
  • HD 5850 (OC+1.15V) = 875MHz Core / 1175MHz RAM
  • HD 5850 (OC+1.225V) = 925MHz Core / 1175MHz RAM
  • GTX 285 (Stock) = 666MHz Core / 1512MHz Shaders / 1242MHz RAM
  • GTX 285 (OC) = 692MHz Core / 1512MHz Shaders / 1332MHz RAM

The Radeon HD 5850's overclock yielded 3500 points.

We ran 3DMark Vantage with PhysX acceleration enabled and disabled to show the difference it could make. The results for the GTX 285 with PhysX disabled are valid for any game which does not use PhysX acceleration, and the results with PhysX enabled are valid for games which do make use of PhysX (Batman: Arkham Asylum, for example).


Even when overclocked, our HD5850 is clearly not as capable as our GTX 285 in applications written to use OpenGL. In games such as Doom 3, the GTX 285 definitely has the edge.


Our 5850 shows a very clear increase in DirectX 11 performance when it is overclocked. No scores were recorded for the GTX 285 as it is limited to DirectX 10; this rendering mode greatly reduces Heaven’s scene detail, allowing the 285 to process the benchmark more quickly, thereby skewing the results.


Our Far Cry 2 testing shows an interesting discrepancy in the 5850’s numbers. The average and minimum frame rates both increase as the card is overclocked, but the maximum frame rate recorded the highest number at stock speed.


With an average overclocked frame rate of about 35 frames per second, the 5850 answers the age-old “can it run Crysis?” question with a yes. Our GTX 285’s average of 23 is below the playable threshold of 30 FPS.

Final thoughts

Overclocking the Radeon HD 5850 is a fairly simple process: Juggle the core frequency and voltage with utilities from AMD and MSI, then test with Furmark and Heaven. Finding the right combination of core and memory frequencies with this process shouldn’t take more than a day, and the benchmarks clearly indicate that the effort is worth it.

In all, the Radeon HD 5850 offers tremendous value for the dollar. It is less expensive than inferior boards from NVIDIA, and it offers overclocking headroom that can push it into Radeon HD 5870 territory. Based on these merits, we can confidently say that the 5850 is the market’s reigning price/performance champion.

You can purchase the Radeon 5850 through our affiliate, Newegg.com, as well as at other online stores or retail shops.


  1. Bandrik
    Bandrik It's always nice to get a little more than you paid for. Awesome work, Bean. That was quite a detailed writeup - looks nice!
  2. Cliff_Forster
    Cliff_Forster Wow, those framerates are at max detail 1080P at 8X AA. Thats pretty nice.
  3. lordbean
    lordbean Yeah... since I was only giving each card one quality setting run per game, I figured... let's go for maximum stress.
  4. JeGX Hi,
    please try to point FurMark download link <a href="http://www.geeks3d.com/20090703/furmark-1-7-0-the-bad-boy-of-graphics-cards-utilities-is-back/"; rel="nofollow">HERE</a>.

    Nice tutorial!
  5. lordbean
    lordbean Thank you for pointing that out, I didn't realize my link for Furmark wasn't working. :)
  6. MathieuB Awesome tutorial Derek. Radeon video cards sure have come a long way, especially regarding overclocking/overvolting that can now easily be done via software. No more "pencil mods" or soldering necessary =D
  7. MAGIC
    MAGIC Now, if they were just in stock so we could buy them.

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