Nuts and Volts

Unleashing New Zealand | HD 7990 | Part 1: Power limits and Temps

Today's the day, after months of waiting for the last pieces to ship, the last piece of the puzzle finally turned up. Pretesting and overclocking the HD 7990.
Funny that the HD 7990s codename is New Zealand, despite it not technically being a "Tropical" Island for AMDs nomenclature for these GPUs. (NZ is considered a "Sub-tropical" island.)

I found it fitting being a kiwi that I should take first with this card; I have a long way to go before I can get gold though. Perfectly segueing into the next part...

Overclocking; Giving the card a spin in FireStrike with the power limit maxed out and voltage slider cranked to a WhOoPiNg 1.3v, the core maxed out at 1150MHz on both cores and memory at 1650 MHz. Final FS score below \/ , TES disabled along with other tweaks etc. 8th place aint bad and with a better CPU like a 5900X I would be sitting around 5th place. 

FireStrike Score

My lil Ryzen 5 3600 is trying its best but should retire soon. The bad single threading performance isn't helping in tests such as Heaven and Vantage...

Temps were interesting; even with the 180 watt power limits in place for each of the cores, the temps were surprisingly hot at 45-50c during FS (Room ambient at 17c), VRM was reaching 60-65c. I made sure I was running max fans and pump speed for OPTIMAL thermals. I have a couple theories' on why the temps are so high:
1. Bad contact on the die either from thermal pads or the metal shim
2. MORE COOLING!!!
3. Waterblock design

Regrettably, I don't have the EK water block for comparison, which I would have loved to include. The rest of the cooling loop consists of a PE 360mm CoolStream radiator, SPC 160 Pump/Reservoir combo, CoolerMaster SickleFlow fans, EK Classic STC 10/16mm compression fittings, ZMT tubing, demineralized water, and of course, the XSPC HD 7990 water block (using GD-900 thermal paste and ADWITS thermal pads). Given the elevated temperatures, I'm likely to disassemble the setup once I've either removed the power limit or completed all desired benchmarks. Ideally, I won't need to "delid" the cores if the waterblock is designed to make proper contact with only the cores. The VRM temperature makes sense since the block's internal design lacks a flow channel over the Vcore VRM area. Memory, VDDCI, Display Drive, and the PLX chip are situated over flow channels. While lacking temperature sensors is a frustration, I can reasonably assume they are fine due to their relatively low heat output compared to the Vcore VRM.

Speaking of the Vcore VRM, voltage control!

Using a modified version of Trixx to increase the voltage, I noticed that even at the stock 1.3v, the card was throttling. It seemed like an easy fix, so I turned to VBE7 to address this. I made sure to keep copies of both the master and slave BIOS. After flashing both, GPU-Z displayed no changes. I tested FireStrike again to verify, and the card was still throttling at 1150MHz. I downloaded the supposedly flashed BIOS to check if it had even flashed. While VBE7 indicated an increased power limit, the changes weren't reflected in GPU-Z and monitoring. I attempted to increase the limits using HxD and guidance from BZ's blog post. Nada, AMDVBFlash complained that for some cursed reason that it couldn't find the file?!? 

I'm guessing it's probably a mixture of the last driver version AMD put out along with how the drivers deal with the card's power limit. Attaching the EVC ain't gonna help yet until I'm hitting a current limit from the controller itself. Until then I'm going to keep looking for a way to remove the power limit and really let the HD 7990 stretch its legs. Even at 1150 MHz I still got pretty good eff despite dropping clocks left and right, however I can imagine once it's removed my eff is going to go through the roof. 

If any of ya'll have a solution please let me know below or on discord (HWbot Discord server) ❤️

Once I throw on some custom timings and voltage control for the memory this card will finally be running at the speed it should have been a decade ago.

Next steps for this are going to be removing the power limit, memory timings, EVC, and better cooling. That first place is going to be mine!