Beginner Guide To Overclocking An ATI 4850

[Chezz]

Over the years I have spent much time on-line utilizing forums to assist me with my many adventures into computer modifications, so it is time I gave back. In this posting I will show you the tools I used to overclock an ATI 4850, and the links to such tools, as well as the overall outcome of my experiences.

WARNING: What I am about to show you will void your warrenty and possibly damage your video card – proceed at your own risk, and have fun doing so…

Here is a quick summary of what was involved along with my results:

Card Model Used: ASUS EAH4850

Modifications
Installed Aftermarket Cooler: Zalman GV1000
Perfromed Bios Flash: Increased GPU, Memory Clock, and GPU Voltage
Performed Pencil Voltage Mod on GPU and Memory

Final Clocks
GPU Clock: 780 Mhz (ATI Tool Artifacts Stable and 1 hour Crysis Benchmark Stable)
This one is for FYI: GPU Clock: 800 Mhz (ATI Tool Artifacts Stable BUT Crashed Crysis Benchmark < .5hr.)

Cooler

The stock cooler temperatures are extremely high, so if you want to overclock your 4850 a new cooler is a must. I chose the Zalman GV1000, a great performer and it fit great. Here are my temps.

Idle Temp: 42°C
Load Temp: 58°C (Crysis Benchmark for about 1 hour)

Here is the link to the cooler:

http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=10007804&prodlist=froogle

One additional thing I did to improve the cooling was to cut the heatsink off the stock cooler and leave it on the chips at the end of the card (see the picture below). I originally ran without the heatsink on the chips and they did not get hot at all, but I figured it was free; so why not put it on.

QUICK TIP: Remove the thermal tape from the stock cooler and put it aside and use a hacksaw to cut the heatsink off, then file it clean. Re-apply the tape and use the stock screws to screw the heatsink down.

NOTE: On the stock cooler the chips on the end of the card share the same heatsink as the GPU. I found that the heat from the GPU made these chips get VERY hot. With my new setup I found that with or without the modified heatsink on the chips, they do not get anywhere near as hot…FYI

See the thumbnail below for an image of the cooler modification.


Overclocking Tools

Here is a list of all the software tools I used and a brief summary of their uses:

ATI Hotfix: Latest ATI drivers
Link: http://support.ati.com/ics/support/default.asp?deptID=894&amp;task=knowledge&amp;questionID=31542

GPU-Z: Great tool for gfx card…save bios from gfx card and read clock speeds and temperatures
Link: http://www.techpowerup.com/gpuz/

RBE: Modify and create new Bios file (this is where you change your clocks, voltage and temperature)
Link: http://www.techpowerup.com/downloads/Utilities/RBE/

Winflash: Bios flash utility used right in Windows to flash your new Bios into your gfx card.
Link: http://www.techpowerup.com/downloads/1062/Winflash_2.0.1.1.html

ATI Tool: First tool used to check if overclock is stable; if this fails it’s time to drop clock speed.
Link: http://www.techpowerup.com/downloads/Tweaking/ATITool/

Crysis Benchmark Tool: Great test of overclock stability (need Crysis to run)
Link: http://downloads.guru3d.com/download.php?det=1791

Futuremark 3Dmark06: Another tool to check if overclock is stable.
Link: http://www.techpowerup.com/downloads/Benchmarking/Futuremark/

Lets get started…

Pencil Mod:
The purpose here is to increase your voltage of your memory and your GPU. The actual mark of the pencil acts as a wire (with some resistance) and creates an additional circuit for current to flow. This is not exactly the best way to control a circuit; however, unless you have the correct equipment and a steady hand, this is the easiest way to mod. In the near future I may go the 100 Kohm pot route, but for now the pencil will do.

NOTE: If you only want a mild GPU overclock, 700 to 730, you may want to skip this section and move to the Bios Voltage modification. The Bios modification will get you about 1.2 Volts.

Here is the link that shows you where to add the pencil marks.

http://www.techpowerup.com/articles/overclocking/151

Here is what I performed:

GPU Voltage Mod (pencil): Performed 1st mod across surface mount component for <1.4 Volt increase
Memory Voltage Mod (pencil): Performed this one and my system (be sure to see notes about applying too much pencil)

Application Notes:
Pencil Type: I used a number 2 HB. I found some people that recommended this type and others that felt HB types were not as good as B types.

Application: The goal with the pencil mod is to create a circuit from one end of the component’s metal surface to the other, so apply the pencil mark by scraping the pencil back and forth from one end of the component to the other until you see some transfer of pencil. I did it about 5 times. After that I blew the loose dust off with an air can. You do not want any loose dust creating a new circuit where you do not want it!

NOTE: Yes, you can put on too much pencil for the memory voltage mod. After applying the mod for the memory voltage my computer would no longer boot; it kept turning on and immediately shutting off. I then took several dry cotton swabs and cleaned the component until no pencil showed on the swabs. This seemed to work; I was able to boot my computer and get an additional 50 Mhz out of the memory!

IMPORTANT: Make that pencil nice and sharp…you do not want to get any of the pencil on the nearby components.

As I mentioned before this is not an accurate way to control a circuit and depending on the type of pencil and the amount of pencil material you put on the component will change it’s resistance properties. If you want to know exactly how much you are increasing the voltage the above link shows locations on the board to measure voltage.

BIOS Modification

Here is a list in the proper order to flash the Bios with updating clocking information:

1. Update ATI driver using Hotfix link.
2. Install GPU-Z. Select “Bios Version/Save To File” as shown in image (little green arrow). This will save your current Bios so you can modify it.
3. Open RBE tool and load saved Bios from GPUZ. NOTE: If you do not see the file when you try to open the saved Bios then change the “Files of type” from “Bios files(*.rom;*bin)” to “All Files”.
4. Go to “Clock Settings” tab.
5. Uncheck the “Locked” field.
6. Modify the clock speeds and voltage in Clock Info 3, 6, and 9 to your desired values. The maximum hardware voltage is believed to be around 1.2 Volts, so I set it to 1.3 to make sure I get the maximum. This seems to be common practice in the forums. In the thumbnail image below you can see where I put 780/1100/1.3 as my overclock values.

QUICK TIP: If you want to do a lot of experimenting with the different “Clock Info” fields you may be able to underclock at times even further than 500/750 Mhz. However, be cautious these values could cause problems. I found by leaving Clock Info 9 at standard values caused my system not to see the overclock; this lead to HOURS of frustration!!


7. Save Bios as a different name than your original.

IMPORTANT: Make sure you save the new Bios to a different name just in case you want to reload your old one.

8. Open up your ATI Catalyst Control Center (this is installed with your drivers and the icon is on the bottom right of your taskbar.
9. On the left click “ATI Overdrive”, click the key icon and unlock the overdrive. Uncheck the “Enable ATI Overdrive” field and hit apply.

IMPORTANT: Uncheck the “Enable ATI Overdrive” field.

10. Open ATI Winflash, click “Load Image”, and select the new Bios file you created in RBE.
11. Hit “Program” and the Bios will be flashed.

IMPORTANT: Do not shut your computer down until the Bios flash is complete.

NOTE: Some people prefer to flash in a Dos based environment and not in Windows. If the flash is interrupted your gxf card Bios may get corrupt and not function. It may not be necessary, but I made sure the ATI Catalyst Control Center was shut off in the bottom right taskbar and I did not do anything with my computer during the flash. I re-flashed my gfx card about ten times with now problems, so it definitely works well.

12. After the flash your computer will need to be rebooted.
13. Upon reboot, open up GPU-Z and in the main tab, “Graphics Card”, check that the GPU and Memory clock speeds are at the overclock values you changed them to.

TROUBLESHOOT: If the speeds are not showing up do the following (I know this from experience!)
- Make sure the ATI Overdrive is off
- Did you add the overclock info into the Bios “Clock Info 9” in RBE?
- If the above two do not work go into Control Panel, Add or Remove Programs, and select to remove, “ATI Uninstall Utility”. A window will pop up, select, “Completely Remove All ATI…” After reboot, and re-install the ATI Hotfix.


Stability Testing

In this section I will show the tools I used and the order of testing I performed to determine a successful overclock. Throughout the stability testing open GPU-Z and select the “Sensor” tab. This will show you temperatures and the clock speed.

NOTE: Your gfx card clock speed in GPU-Z. Sensor Tab, will vary depending on application demand. When you use ATI Tool, the speed shown should max out to your overclock settings.

Here are the stability tests in a good order to run them:

1. ATI Tool – Open the tool and click “Scan for Artifacts”. If you have an unstable overclock you will immediately see yellow artifacts appear on the block image and the message on the bottom of the block image will no longer say “No errors”. I usually only let it run for 20 seconds or so. This is really a first pass test; the true test is Crysis.
2. Crysis Benchmark Tool – Set “Custom Resolution” and AntiAliasing to desired value then select the double arrows to add the run to the Queue. In this utility you are able to set a batch with different test AntiAliase and Resolution settings as well as adjust the Demo Loop. Once the desired tests are added to the Queue, select “Begin Benchmarking Run”.

See the thumbnail below for an image of the Crysis Benchmark application.

Signs of Instability: When running the Crysis benchmark I found that if you see columns of black throughout the run, your memory clock is too high. If your GPU speed is too high (or voltage too low) the failure modes while in the benchmark I have seen have been in the form of the system screen going black or the application shutting down. When my screen went black I had to manually force a reboot.

NOTE: If you are in a 3D graphic application (game) and the application randomly shuts down it may be a sign of an unstable overclock. The ATI software includes what is called “ATI VPU Recovery.” This is an application that monitors the performance of the gfx card and if it sees the card crash it will try to reload the gfx drivers so your whole system does not crash. It has worked successfully for me a few times.

3. 3Dmark06 – The first two applications listed are my main stability checks, but I put 3Dmark in as an additional option. If you are going to use 3Dmark, then I would recommend running several loops. I am not able to comment on the exact failure modes that could be associated with an unstable overclock using 3Dmark; however, I would assume they would be comparable to the Crysis Benchmark.

Benchmarks

This is what it is all about…but they are not complete yet… I started running some benchmarks against my BFG 8800 GTS 512mb OC. Once I get them finished I will post them here.


Final Comments

Well I hope this guide helped to consolidate some of the information out there. What next – I will add some benchmarks, and if I feel up to it I may perform the 100 Kohm voltage mod to try to reach the 800+ Mhz GPU mark.

Keep it save…and try not to smoke anything; but if you do, have fun doing so…