flyproductions
macrumors 65816
True!
...but don't most of these require pixlas mod or similar solutions anyway?
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MP All Models AMD Radeon RX 6800 XT / 6900 XT for macOS?
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tsialex
Contributor
Reference versions of VEGA 56 and RX 5700XT are both cards with 8+6-pins connectors that 95% of users can run safely with just a PowerLink, obviously until the moment you start to run benchmarks/FurMark stress test.
Couldn’t you just get a RX6600XT, flash it and use that?
If you are okay to upgrade to Monterey then that card works flawlessly.
Mac Hammer Fan
macrumors 65816
flyproductions
macrumors 65816
So i did some more testing to the case and it gets even stranger.
Out of curiosity, i tried with my High Sierra install with no OC present. Sure no driver support / accelleration to expect. But i just wanted to know if the card is giving a picture in HS at all. And voilà! With the same adapter configuration that went black after preboot with Monterey / OC, the card boots nicely to the desktop showing full 2.560 x 1.600 on the Cinema HD! Of course also showing bootscreen as the "Enable GOP" is injected to the card's bios.
So problems seem to be related to Open Core or Monterey. Maybe some particular combination of boot-args could solve it. But i have no idea. ☹️
AlexMaximus
macrumors 65816
Hi Lance,
Attached you will find the Heaven Benchmark with the same settings you used. Its about the same as your Sonnet. Though I can use a single SSD in Slot #2, the dual Crest I/O bridge card would give it an additional boost. But then most fans would be obstructed, so I decided to use only the very short single SSD PCI card so far to allow ample airflow.
AlexMaximus
macrumors 65816
Here is your answer how the balancing works. There are resistors on that little board as well, which makes it an RC-Circuit solution. Here is the functionality and scientific background down below. (High-pass/Low-pass and such)
RC circuit - Wikipedia
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macsoundsolutions
macrumors regular
Nice, thanks for posting. I just re pasted my Northbridge yesterday and both 5690s so will run it again, but don't expect it to change anything. My Northbridge was running very hot though, got it down 10c but still running at about 80c with stock Apple fan control. Do you know what your Northbridge temps are? If you have iStat you can see them. Bumping up my fans a bit I get it down to 66c in Mac OS. How are the temps on your 6800xt, mine are idol at about 66c.
A comparison of config.plists show that the boot_args for the two cards are managed differently by OCLP. So it seams that “Failed to find Device path for dGPU 1” has no effect on the functionality of the RX 6600 XT because for this card the values are managed by the boot_args.
Just a short question about my AMD Sapphire nitro+ RX 580 which has 8+6-pins:
From the web I’ve got the information that it is sufficient to power it with 2x6-pins-outputs of the MacPro5,1-motherboard to the 8-pins-input of the card.
Is this correct, or how would I power this card differently using both the 8 and 6 pin power inputs?
hwojtek
macrumors 68020
Okay, as I understand: 6pin-to-6pin and 6pin-to-8pin. -- Does it make a difference to power the card this way vs. 2x6pin-to-8pin?
hwojtek
macrumors 68020
This said: I have my 6 pin outputs from the motherboard hooked up to EVGA Powerlink (two 6-pin inputs) and the other end of the Powerlink has now a single 8-pin output and a single 6-pin output.
I've never had any power issues with R280 (dual 6-pin) and now RX570 (6-pin and 8-pin, needed a minor trimming of the plastic fan enclosure to make the Powerlink fit).
This system is future proof as I also ordered an additional 8-pin output for the Powerlink (only one comes in the package) so I'm ready for dual 8-pin cards.
I've never had any power issues with R280 (dual 6-pin) and now RX570 (6-pin and 8-pin, needed a minor trimming of the plastic fan enclosure to make the Powerlink fit).
This system is future proof as I also ordered an additional 8-pin output for the Powerlink (only one comes in the package) so I'm ready for dual 8-pin cards.
AlexMaximus
macrumors 65816
Hi Lance,
I may got just the thing. Down below see the link to the Northbridge-cooling-self-help-group.
I got myself inspired by Tsunami's solution, so I have ordered that 3D part in Belgium. Since I am located in Germany, shipping wasn't an issue. However I am low on time and not all USB parts for my 5V fan power solution have arrived yet. I hope I can post some results beginning of April when I get more time again.
Regarding the GPU temps, I do not get a read out on Mac Fan Control. It seems this card does not support that feature.
However, I had many many GPUs in my rig during those last seven years. This card defenelty runs very cool. To my surprise the fans don't speed up very often. My old Vega IIV was running way louder in 20219 than this thing. I suspect the Alienware card is somehow a bit throttled down by the firmware because of the ultra cramped Alienware Mini tower, where it used to come from. Hence why this particular card is a dual slot.
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macsoundsolutions
macrumors regular
Hi Alex, My RX6800XT is very quiet until I load a game then it takes off like a rocket but can be tweaked. I have put an app called RadeonGadget in my dropbox for you. It gives you GPU temps in the mac os menu bar, it comes in Martin Lo's opencore package with the other files. https://www.dropbox.com/sh/q9krx0fmxq8az6g/AADDUyGs47E6d2aa6ou0MaWNa?dl=0 I have seen that fan kit before looks interesting let me know how it goes thanks,
flyproductions
macrumors 65816
So one other question to this: Does it make any difference wether the PowerLink is fed by two mini-6-pin -> single-8-pin cable to one of it's inputs or two seperate mini-6-pin -> 6+2-pin cables to both of them?
Would tent to say logically no, as it all ends up on the same two rails anyway. But maybe i am (again) missing something. I'm asking cause i allready have the dual -> single and planing to finally fet one of these 6800 founders.
For each option, count the number of 12V lines and ground lines. The minimum of those two counts determines the max current the option can take (if the wires are all the same gauge).
The two options should probably be equal, since 6 pin is supposed to handle 75W and 8 pin is supposed to handle 150W. 8 pin doesn't have twice as many wires, so it must be using thicker wires.
It may be that the option that can handle the least current is still sufficient.
Anyway, if it doesn't melt then it's probably ok.
tsialex
Contributor
Your limitation is always the PCIe AUX connectors power capabilities, having more wires won't make the backplane to feed more power. Two 6-pin to miniPCIe 6-pin cables already connects every power and ground connection to the eVGA Power Link.
Btw one thing that I've notice over the years, some dual miniPCIe 6-pin to 8-pin cables have less wires connected than two 6-pin to miniPCIe 6-pin cables.
wnt today for upgrade for RX Vega 56 from mini-6pin to 8pin + mini6pin to 6pin
to dual-mini6pin to 8pin + dual-sata-to6pin adapter;
now heaven benchmark would run "stable", eg. not crashing, as it did before, but there were some artifacts, so maybe the card still get too less power or maybe the card (aquired only second hand) is already bit faulty.
Benchmark was not so bad, with around 110 fps maybe, 2700 points,at standard presets.
to dual-mini6pin to 8pin + dual-sata-to6pin adapter;
now heaven benchmark would run "stable", eg. not crashing, as it did before, but there were some artifacts, so maybe the card still get too less power or maybe the card (aquired only second hand) is already bit faulty.
Benchmark was not so bad, with around 110 fps maybe, 2700 points,at standard presets.
h9826790
macrumors P6
In general, unless some wires in the 6pin / 8pin cables are not connected properly. The card should just draw whatever it need until the cMP shutdown. "Not enough power" should not be the root cause of the artefacts (assuming there is PowerPlay table to limit the core voltage, etc).
If possible, you better run the benchmarks / stress in Windows. So that you can monitor much more parameters in real time. In Windows, you can see if the card is power throttling, or temperature torottling, or something else.
If that's a used card, and having artefacts in benchmarks. I will focus on the follow two areas first
1) temperatures
2) firmware
Overheat is always the first suspect when a GPU doesn't work properly under stress. If in doubt, you better repaste the GPU, and replace all thermal pad. Also, the cMP can be run with side panel open, check the card's fans are running properly.
For used card, it may be flashed for mining. In that case, the card may has higher than normal compute performance in mining. However, may produce artefacts in 3D. If not sure, backup the ROM, and then flash it with a factory ROM (can be download online, or ask the card manufacture to send you a copy).
@h9826790 82679 thank you for the hint,
in windows 11 (MacPro4,1/5,1) the Graphics card, behaved fine, no artifacts, very good temperatures, and same benchmark yielded around 145 fps or nearly 3700 points, which is quite better than on MacOS. So it seems the problem is more on the Mac side of things, rather than on the GPU, if i may say so.
in windows 11 (MacPro4,1/5,1) the Graphics card, behaved fine, no artifacts, very good temperatures, and same benchmark yielded around 145 fps or nearly 3700 points, which is quite better than on MacOS. So it seems the problem is more on the Mac side of things, rather than on the GPU, if i may say so.
h9826790
macrumors P6
In Windows, in the AMD Radeon Software, go to the PowerPlay settings. There should be a setting for you to set the max power.
In macOS, this number is read from the VBIOS. For Vega56, may be 50%, may be 30%, depends on the card. Which means, the max power draw is 150% or 130% etc.
In Windows, the Radeon Software will use that number to define the max possible setting, but set the default to zero (which means 100%). Therefore, you need to manually set that back to the max setting in order to simulate the card's behaviour (temperature etc) in macOS.
Of course, it can be purely software issue. However, OpenGL is quite solid in macOS, and the Unigine Heaven benchmark is a known good software in macOS. Many many users can run that without artefacts (including Vega56 users). Therefore, IMO, the possibility of software issue isn't that high at this moment.
Here's a little progress report on my efforts installing an RX 6600XT on two 2009 and 2010 MacPros.
As a first step, I focused on the MacPro4,1>5,1 with Monterey and made various attempts with the installation of Opencore and Post Install Root patches and with adjustments in the Config file.
I patched the BIOS of the RX 6600 XT three times, once with the original BIOS, then with the version from Syncretic and finally with the BIOS from Techpowerup.
Unfortunately, all this did nothing. Although the card initially worked excellently after the system start, it regularly crashed when rendering projects in DaVinci Resolve and also brought the operating system to its knees.
The crash was initially always announced with periodic horizontal stripes until DaVinci Resolve finally crashed. After the crash, the card then produced colourful patterns that spread across the screen like snowflakes.
After causing the RX 6600 XT to crash even on a Windows 11 system, I finally sent it back.
It's a shame, really, because my MacPros run so stably with two RX 580s under Ventura and Monterey and deliver so much performance that I see no reason to buy new machines.
Only in video editing a 6x00 card would bring a welcome increase in performance.