Question Dual Radeon VII won't post

Jul 6, 2019
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So I have a 1.5 year old R7 1700 build with a b350 tomahawk and decided to switch from a 1080ti to a Radeon VII. All was well, so well in fact I got a second Radeon VII to hook into my build. I plugged it in and my system would not post and stays stuck with the VGA motherboard light lit up. I took out my 1st card to test the 2nd one and it works like a champ. I inserted the 1st card into the secondary slot and VGA light. I tried each card in the secondary slot and VGA light. Does this mean my motherboard has a toasted secondary port? What else can I try? Oh my power supply is 750W, I know that's probably not enough but I should at least get to the BIOS screen, no?
 
Jul 6, 2019
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Well the minimum psu that amd reccomend for a single vega vii gpu is 750w no way you can run two of them with this psu.
You think that’s all it is? Shouldn’t I at least be able to post? And why won’t either of the cards work in the secondary slot by themselves?
 
Jul 6, 2019
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Why you need two Radeon 7 in the first place?
Oh I don’t even need a desktop computer I’ve just always wanted one. When I’m not gaming I was mining with my card and the R7 was making enough each day to pay for itself in less than a year so I thought it would be fun to have two since I had the space inside my case. What do you think the problem is? I know the psu is too week to support both cards at full load but I should make it into the bios at least, right? And why won’t a single card work out of the secondary slot?
 

digitalgriffin

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You'll need a SOLID 850 at least like a Seasonic Focus+ or better. 1kW would give you head room.

Why even try to post with 750 when you know @ speed that won't be reasonable. Any way 10:1 your PSU is powering down because of over current protection on powerup. Some cards do boot @ full speed and then immediately clock down. So a current surge isn't a surprise.
 
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Jul 6, 2019
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You'll need a SOLID 850 at least like a Seasonic Focus+ or better. 1kW would give you head room.

Why even try to post with 750 when you know @ speed that won't be reasonable. Any way 10:1 your PSU is powering down because of over current protection on powerup. Some cards do boot @ full speed and then immediately clock down. So a current surge isn't a surprise.
Ah so it won't post because it might be protecting itself, well that makes sense, I just wish I could get a single card to post from the second pci-e slot to confirm it's working before I order a better power supply.
 

digitalgriffin

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Ah so it won't post because it might be protecting itself, well that makes sense, I just wish I could get a single card to post from the second pci-e slot to confirm it's working before I order a better power supply.
That's easy. Just pull the card in pcie slot 1.

Also make sure your bus depending on chipset had enough lanes for that second slot. A lot will allow you to have 2 x8 with not much else depending on how the lanes are allocated.
 
Jul 6, 2019
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I tried pulling the card from slot one but leaving the other card in slot two and it just gives the vga warning light. That’s why I’m concerned it’s my motherboard. I think the second slot operates on pci-e gen 2
 

digitalgriffin

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I tried pulling the card from slot one but leaving the other card in slot two and it just gives the vga warning light. That’s why I’m concerned it’s my motherboard. I think the second slot operates on pci-e gen 2
Pci gen 3 is backwards compatible with gen 2. It's part of the spec. Remove card in slot 2 and put in slot 1 and see what happens.

What make and model motherboard are you using and what cpu?
 
Jul 6, 2019
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Pci gen 3 is backwards compatible with gen 2. It's part of the spec. Remove card in slot 2 and put in slot 1 and see what happens.

What make and model motherboard are you using and what cpu?
I've tried both cards in both slots one at a time and they both work in the main x16 slot/PCI_E2 but the secondary PCI_E4 is a no go with a vga light.

Board: B350 MSI Tomahawk Arctic
BIOS: MS-7A34 V17.I BIOS Release from 2019/1/30
VGA: XFX Radeon VII
PSU: EVGA Supernova 750W G2 (70.8A 12V rail)
CPU: AMD Ryzen 7 1700
MEM: G.SKILL TridentZ RGB Series 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3200 (PC4 25600) Desktop Memory Model F4-3200C16D-16GTZR
HDD/SSD: 1x Samsung SSD 850 EVO 500GB, HGST HDN726040ALE614 4TB 7200 RPM 128MB Cache Sata 6.0Gb/s
COOLER: Stock Wraith Spire
KEYBOARD: Blackwidow Chroma v1
MOUSE: ROG GX1000
OC: None
OS: Windows 10 64bit Professional
 
Jul 6, 2019
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Yeah according to that watt website my peak power draw is something like 853+ watts do I’ll definitely need to upgrade that, any suggestions or links would be appreciated 😁
 

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