Sapphire HD5850 Xtreme / HD6850 Volt-Mods (vGPU & vMEM) - Overclock.net - An Overclocking Community

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Sapphire HD5850 Xtreme / HD6850 Volt-Mods (vGPU & vMEM)

 
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post #1 of 3 (permalink) Old 06-09-2011, 03:57 AM - Thread Starter
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Sapphire HD5850 Xtreme / HD6850 Volt-Mods (vGPU & vMEM)


overview

The PCB is identical to those of HD6850s with AMD reference design. This means these mods can be used for HD6850 as well
A 4-phase switching regulator, which is located between the GPU and output panel, controls the GPU voltage. For the memory a simple single phase switching reg is beeing used.

uebersichtxofd.jpg




voltage measurement

output caps of both switching regs are always a good spot for voltage readings. though the little MLCC at the back of VRAM ICs and GPU will give you a more accurate reading.

messpunkte5trg.jpg


If u are using software like Trixx to adjust vGPU be aware that those values are different to the real voltage. Here's a table with exact measurement:

tabelleaiw8.png
*Spannung=voltage
*Last=load




vGPU mod

IC: CHiL 8214
FP Pin: Pin 4 (VSEN)
original resistance: 12.4 Ohms
recommended VR size: 500 Ohms

vgpuyrdb.jpg
*Masse = ground
*put a 500 Ohm VR between FB Pin and GND




vMEM mod

IC: APW7165
FP Pin: Pin 6
original resistance: 5010 Ohms
recommended VR size: 200k Ohms

Pin 3 is a good ground spot. A pencil mod is possible alternatively

vmem2t04.jpg




overclocking

I did some tests with the integrated benchmark of Crysis. Tested in 1920x1080px, DX10 very high details, HQ 16:1 AF and no anti aliasing.
Max. clocks at default voltages are 850MHz(GPU)/1300MHz(VRAM). With an increased GPU voltage of 1.29V(real) and 1.66V VRAM voltage it runs completely stable and without any artifacts at 970/1340MHz. For now I didn't tested more volts because of the stock cooler and high ambient temps.
Benchmarks will run with more than 1000MHz GPU clock.

hd5850_crysis_970-1340molh.jpg
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post #2 of 3 (permalink) Old 06-12-2011, 10:00 AM
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Pretty nice VRM for a low-end GPU.

Never really been an ATI fan, but they typically have nice PCB layouts and clock like mad.

I think you should duct a leaf blower onto your air cooler...wait till liek 2am and fire it up for some hardcore OC action ..really piss of the neighbors.. and see if you can F5 your CPU-Z before the cops show up!!
~CL3P20

Do the opposite of what this guy just said if you want the best results you can get
~el gappo


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post #3 of 3 (permalink) Old 06-12-2011, 03:18 PM - Thread Starter
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I am more a Nvidia fan too but I have to say that both have their advantages and disadvantages. Some ATI cards are very nice and easy to handle for overclocking.

Btw I would never call this low-end. With a slight overclock the performance is similar to a HD6870.
THIS is up-to-date low end biggrin.gif
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