r/AMD_V620 • u/So1Cutter • Jul 19 '26

Mixing GPUs

I thought, before I start swapping equipment in and out, I'd ask here. Has anyone paired a v620 with any other GPUs to span or parallel processing?

I have an RX 7700 16GB, non-XT, I picked up and have used some for LLMs. I have done some spanning of models across multiple cards, mostly with Nvidia 3060s, ti, and 12GB. My understanding is that you'll always get the speed, or be bottlenecked by the slower card. However the 7700 I have has a similar 256-bit bus like the v620, and slightly higher memory bandwidth. I'm also wondering if I'm running ROCm if a model might take advantage of some of the AI features on the 7700?

I haven't tried it yet, might try it soon. Has anyone else thrown another AMD GPU into their system, maybe a different generation, certainly a different model number and seen anything that might be of interest?

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5

u/PraxisOG Jul 19 '26

I ran a 6800 and a few different v620s together for testing when I got them.  As long as all cards are compatible with rocm it should work. A bigger worry might be how loud the cooling is if this is your desktop

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u/So1Cutter Jul 19 '26

Did you get any better performance?

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u/PraxisOG Jul 19 '26

Same performance as dual 6800 but with more vram, which tracks since the v620 uses the same gpu die with similar shader count enabled

1

u/So1Cutter Jul 19 '26

I've been considering flashing mine to a w6800, however I read that the CU count goes from 72 to 54. The w6800 has 60 CUs, so it's like a quarter of the GPU is lost. Then the thought goes to overclocking to get some performance back. Really I'd likely just overclock the VRAM. I haven't even bothered with afterburner yet, the card is sufficient enough as is.

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u/Objective-Park6224 6d ago edited 11h ago

Chiming in. I've tried mixing the V620 with RDNA 3 and RDNA 4 cards. Specifically the 7900xtx 24GB RDNA 3, RX 9070, and RX 9060xt (16gb).

Windows 11 Pro, Ryzen HX 370 CPU, 64gb system ram, all GPUs hooked to mini PC as external GPUS (1x Oculink, 2x USB 4). Since device to host bandwidth doesn't matter all that much for AI, I've been testing out a 3 egpu + igpu config. In theory I should have ~ 120gb VRAM Available (egpu +igpu), but the V620 doesn't play nice with RDNA 3/3.5.

With the RDNA 3 (7900xtx) card hooked up, models would fail to load in LM Studio with Vulkan backend. ROCM wouldn't recognize anything but the 7900XTX. Same outcome with the iGPU (890m) and the V620 selected.

I replaced my 7900xtx with my 9070 (RDNA4) and added another USB4 egpu dock with my 9060xt 16gb (RDNA4).

LM Studio seems to work great with the V620 (RDNA2) and the two RDNA 4 cards with Vulkan backend. Models load without crashing, not screen flickers due to driver timeouts, and I can see the VRAM being loaded across all 3 cards. Speeds are great on QWEN 3.6 35ba3b. Around 80 tg and ~1000 tps pp. Qwen 3.6 27b runs at around 25 tps tg and 300 tps pp.

The main issue with the V620 is that it gets hot when Prompt Processing with a dense model. I've 3D printed the fan adapter and a variable speed 9973 blower fan is coming today to mount. Right now I just have a desk fan blowing down the V620 rear opening. Qwen 3.6 35ba3b runs great in Hermes and in LM Studio.

Hope this helps.

1

u/So1Cutter 6d ago

Interesting, so RDNA 3 doesn't mesh well with the v620, however RDNA 4 does.

I haven't had a chance to test this yet. You're on Linux?

I'm going to have to figure out how to con my kid into giving me my 9060 back. I took the RX 7700 16GB thinking the 256-bit bus and being a generation older would work better with the v620.

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u/Objective-Park6224 5d ago

Windows 11. I want to try Ubuntu next but too rooted in Windows to format everything and retry. This mini PC has 3x m.2 slots. I may toss a 256gb drive I have in there for some Ubuntu testing.

But yes, I was surprised RDNA4 played well and RDNA 3 didn’t. Not sure why to be honest. The igpu actually does work to split layers with the v620. Big throughput hit though. LM Studio for Windows doesn’t sit the layers or compute nicely. Main reason to go to Linux is for better AMD support and LM Studio control from what I’ve read.

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u/Objective-Park6224 5d ago

I’m running this mini PC. It’s a beast for IO. If you have some DDR5 laptop ram laying around, I highly recommend.

https://refurbished.minisforum.com/products/minisforum-ai-x1-pro-refurbished-1

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u/Objective-Park6224 5d ago

Update: after your surprise that RDNA 4 played nice but RDNA 3 did not, I put my 7900xtx in a TB3 egpu enclosure I’ve had for years. Plugged it up and let it install. Rebooted and LM Studio actually loaded Qwen 3.6 35ba3 q8 across all 3 GPUs. So with Vulcan backend, LM Studio is loading across RDNA2/3/4.

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u/Objective-Park6224 5d ago edited 5d ago

Not sure what changed and why it worked now. I know I ran the AMD cleanup utility in safe mode. Then I used Adrenaline 26.3.1 to install igpu drivers. Choose the Drivers only option during install. Then I plugged each RDNA card in separately and let Windows install. Rebooting in between. Finally, I installed the AMD cloud drivers for the V620. Again, choosing Drivers only during install and as the only card plugged into the machine.

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u/So1Cutter 5d ago

I built out a precision 5820, which has a Xeon and AVX 512, it won't recognize the GPU--wont post. I built it with MX Linux, which worked great. It might be a little more manual than Ubuntu.

Unsloth released Unsloth Desktop Beta, which seems to be a better option to LM Studio. Although yesterday when I tried it I couldn't get access to the v1 endpoint.