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post #5 of (permalink) Old 02-27-2019, 12:58 PM - Thread Starter
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Quote: Originally Posted by AlphaC View Post
Yes it is. Basically Gigabyte decided to dump some money into the GPU cooling (they put a heatpipe into the backplate as a result of the power design) and then cheapen out a bit on the power delivery with two AON6360 as a replacement of sorts of the IRF6894. It isn't as big an issue for gaming or whatnot, but being the only card setup with that sort of power delivery means you inherently use more power. The thermals don't reflect the losses as much since they used 2x low side fets but if you look at Sapphire Nitro results they're at least 10°C cooler even on Vega64.

3mΩ @ 10V , 5mΩ@4.5V V_GS

7mΩ @ 10V, 11mΩ@4.5V V_GS


Reference uses IRF6894 and IRF6811. The IRF6894 has a 0.9 mΩ RDSON @ 10V , 1.4m mΩ @ 4.5V and the IRF6811 has 2.8 and 4.1 mΩ resistance respectively. Q_G (total gate charge) for IRF6811 high side fet is extremely low at 11nC , which means switching is less lossy.

https://www.infineon.com/dgdl/irf6894mpbf.pdf?fileId=5546d462533600a4015355f0cc0 41abc

If you look at other nonreference designs such as the ASUS STRIX version , it's using 60A IR powerstages (https://www.photopoint.ee/en/compute...vega-56-oc-8gb , https://www.hardocp.com/article/2018...aming_review/3, details gained from VEGA64 version https://www.hardwareluxx.de/index.ph...t.html?start=2).

Powercolor's Red devil is essentially the reference design: https://www.guru3d.com/articles-page...-review,4.html , https://www.hardwareluxx.de/index.ph...t.html?start=2

XFX's Double edition is basically reference Nano with cut down the phase count to 8 (instead of 12): https://www.overclock.net/forum/26648417-post5895.html , https://hardforum.com/threads/xfx-ve...vesty.1953602/

Sapphire's RX VEGA NITRO series is 14 phases up from the 12 on reference.

Sapphire also has a RX VEGA Nano based "Pulse" that has a conservative power limit (minor bump from reference) https://www.computerbase.de/2018-03/...as_winzige_pcb

One issue with the reference Vega 56 in general is that the only aftermarket cooler options are pretty much the Raijintek Morpheus II and waterblocks of some sort (whether they are Asetek AIOs , Alphacool Eiswolf AIOs, or full custom). This is due to HBM memory and the VRM layout. Arctic Accelero Xtreme air cooler doesn't seem to work apparently (that is an option instead of a waterblock for a Nvidia card).

I feel as though Sapphire was the only vendor that did VEGA56 and VEGA64 justice. They have one conservative card that's one centimeter longer than reference and an overkill overclocking powerhouse with 3 PCIE power connectors and a massive triple slot heatsink that only needs ~1200RPM fan speed.
Thanks for the break down. I'm just starting to get into the Extreme OC area. The most OC'ing I've done is Custom bios editing for my old r9 390x on an AIO. Anyways, yea, i heard bad things about these gigabyte cards. I was hoping I could get a waterblock for it while retaining the stock backplate, but that might not be the case..

Official Ryzen 7 3700x Owner!
VEGA 56 with PPT Mod
16GB Corsair Vengeance LPX 3000
Asrock X370 Pro 4
NZXT h500i
All on a custom water loop
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