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VillasManzanill

macrumors regular
Original poster
Mar 7, 2012
133
18
Hello
I have a

RX 580 8gb ROG STRIX Asus (pci e slot 1, its a huge card, takes 2.5 slots)

5770 1gb apple stock (pci e slot 3)

my system is
5,1
X5690 x 2
96gb ram 3 16gb ram slots in each processor

and here my link speed benchmarks of opencl ocean wave 1.61 attached

with only the rx 580 my speed is 3gb speed and
with the 2 gpus it drops down to 1.5gb

Why does it drop down to 50% with 2 gpus?

i have tried the configuration of

rx 580 slot 2
5770 slot 1

Same bad results.

if you know how to fix this it will be awesome
thanks!
 

Attachments

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h9826790

macrumors P6
Apr 3, 2014
16,656
8,587
Hong Kong
Hello
I have a

RX 580 8gb ROG STRIX Asus (pci e slot 1, its a huge card, takes 2.5 slots)

5770 1gb apple stock (pci e slot 3)

my system is
5,1
X5690 x 2
96gb ram 3 16gb ram slots in each processor

and here my link speed benchmarks of opencl ocean wave 1.61 attached

with only the rx 580 my speed is 3gb speed and
with the 2 gpus it drops down to 1.5gb

Why does it drop down to 50% with 2 gpus?

i have tried the configuration of

rx 580 slot 2
5770 slot 1

Same bad results.

if you know how to fix this it will be awesome
thanks!

What it says here?
Screen Shot 2017-09-28 at 08.42.03.jpg
 

VillasManzanill

macrumors regular
Original poster
Mar 7, 2012
133
18
im attaching pics
 

Attachments

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h9826790

macrumors P6
Apr 3, 2014
16,656
8,587
Hong Kong
im attaching pics

In this case, unless you really see a bug performance drop in real application, I wouldn't worry too much about it.

Oceanwave is pretty old now, and no one knows how accurate it can handle multi GPU config.

Anyway, in your case, you better install 5770 in slot 1, and RX580 in slot 2. So that both card can run at x16.
 
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VillasManzanill

macrumors regular
Original poster
Mar 7, 2012
133
18
ok thanks
is there any other program that can do a similar test (pci speed link gpu) as oceanwave ?
with 1 gpu it says my speed its 3gb
 

h9826790

macrumors P6
Apr 3, 2014
16,656
8,587
Hong Kong
ok thanks
is there any other program that can do a similar test (pci speed link gpu) as oceanwave ?
with 1 gpu it says my speed its 3gb

Don'y know, but IMO the best way to test it is to run real benchmarking software.

e.g. Luxmark V3, or Unigine Valley.

Especially Luxmark, It can clearly shows each GPU's contribution. So that it allow you to easy compare if the GPU's performance drop significantly if the 2nd GPU installed.

Also, it can tell if you should install the 2nd GPU (if overall score drops after 2nd GPU installed).
 

VillasManzanill

macrumors regular
Original poster
Mar 7, 2012
133
18
i changed the location of the gpus slots now i have

rx 580 slot 2 system says its at 8x
5770 slot 1 system preferences says its at 16x

whats with that
here screen shots
 

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h9826790

macrumors P6
Apr 3, 2014
16,656
8,587
Hong Kong
i changed the location of the gpus slots now i have

rx 580 slot 2 system says its at 8x
5770 slot 1 system preferences says its at 16x

whats with that
here screen shots

That means Oceanwave actually reporting the correct number. AFAIK, it always report the 2nd GPU's bandwidth.

So, in your case. If RX580 in slot 1, and 5770 in slot 3.

It detect PCIe 2.0 x4, and shows 1.5GB/s

If you put 5770 in slot 1, and RX580 in slot 2.

Then it detect PCIe 1.1 x8, coincidentally equals to PCIe 2.0 x4, therefore, also display 1.5GB/s.

But I really have no idea why the RX580 can only connect as a x8 when you put that in slot 2.
 

irontony21

macrumors newbie
Sep 4, 2017
5
1
New Zealand
The RX 580 that we use are not Apple "Blessed" as they do not contain Apple firmware. This is a known limitation when using generic Windows AMD/ Radeon Graphics cards in Apple Macs. Stop worrying about it and enjoy your new RX 580. (mine is the same max Link Speed is 2.5G)
 

h9826790

macrumors P6
Apr 3, 2014
16,656
8,587
Hong Kong
The RX 580 that we use are not Apple "Blessed" as they do not contain Apple firmware. This is a known limitation when using generic Windows AMD/ Radeon Graphics cards in Apple Macs. Stop worrying about it and enjoy your new RX 580. (mine is the same max Link Speed is 2.5G)

Problem is not 2.5G, but PCIe x8.

Is that a known issue for RX580?
 

VillasManzanill

macrumors regular
Original poster
Mar 7, 2012
133
18
after reboot now they both show as 16x lane
im using os x 10.13
how weird
 

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Appleham

macrumors newbie
Sep 11, 2018
1
0
Hello
I have a

RX 580 8gb ROG STRIX Asus (pci e slot 1, its a huge card, takes 2.5 slots)

5770 1gb apple stock (pci e slot 3)

my system is
5,1
X5690 x 2
96gb ram 3 16gb ram slots in each processor

and here my link speed benchmarks of opencl ocean wave 1.61 attached

with only the rx 580 my speed is 3gb speed and
with the 2 gpus it drops down to 1.5gb

Why does it drop down to 50% with 2 gpus?

i have tried the configuration of

rx 580 slot 2
5770 slot 1

Same bad results.

if you know how to fix this it will be awesome
thanks!
 
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