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Author Topic: Gigabyte 4Gb R9 280X or HD 7950 3Gb : Buying recommendations  (Read 903 times)
SMIKX
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« on: July 19, 2017, 03:26:38 AM »

Fl0r!an & Blacksheep, ( or anyone who has one of these cards in a cMP 4,1 or 5,1 )

I have a chance to buy a 4Gb Gigabyte R9 270X cheap.

I already have a flashed 2Gb R9 270X up and running perfectly.

Two questions for you if you don't mind ..

1. If I flash the 4Gb Gigabyte R9 270X can I expect it to use the whole 4Gb?

2. Will I see any actual benefits using this card ? eg: I use X-Plane 10 a lot.

I can also get a cheap 7950 3Gb .

Which would you reccomend buying?

Thanks in advance.
« Last Edit: July 20, 2017, 12:00:48 PM by SMIKX » Logged

Mac Pro 4,1 upped to 5,1 Dual Quad Core 2.93ghz 17Gb 480Gb SSD TRIM enabled.
HIS HD 7950 3Gb 5.0 GT/s EFI on mDP to DVI + DVI to DVI.
10.9.5 - 10.12.6  - 10.6.8 - Win 7 not Bootcamp. 
AREA 2 port USB 3.1 & Inateck USB 3.0 4 port in OS X 10.9.5.
h9826790
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« Reply #1 on: July 27, 2017, 03:18:20 PM »

Depends on the scenes and setting. I had a 7950 before, and X-plane 10 usually use about 1.7GB VRAM (1440P). By considering it's so close to 2GB. 3 or 4GB is definitely a better choice. In fact, in some occasion, it can use up to about 2.6GB. But I intentionally use a setting that can utilise more VRAM. If not, 2GB should be enough in general.

However, unless you really hit the 2GB VRAM limitation, otherwise, you should not see any significant difference.

The 7950 and 270X perform similarly in real world. And TBH, X-plane 10 is very CPU single thread limiting. By considering you already has a 270X, upgrade the GPU (mainly VRAM capacity) shouldn't help much.
« Last Edit: July 27, 2017, 03:19:54 PM by h9826790 » Logged
SMIKX
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« Reply #2 on: July 28, 2017, 01:40:54 AM »

Nice to meet another X-Plane fan.

I read this post after reading your reply to my prior post.

I am still curious to see for myself how X-Plane framerates are affected my the PCI 2.0 mod .. in any case it will be a good learning experience. My R9 270X only cost ¥6,500.

My next card will be either an R9 280X or a Sapphire HD 7950 - they're still both quite expensive here in Japan.

I came across this 4Gb Sapphire model but the seller has written " 7970" in the description which would be wrong http://www.ebay.com/itm/AMD-Apple-Radeon-R9-270X-4GB-Graphics-Video-Card-Mac-Pro-3-1-5-1-OS-10-13-7970/253055296761?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D41451%26meid%3D3eca0e8c68924a8d8cd9fac870de2b23%26pid%3D100011%26rk%3D5%26rkt%3D12%26sd%3D321610931161

Still pricey. I'll wait a bit more.


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Mac Pro 4,1 upped to 5,1 Dual Quad Core 2.93ghz 17Gb 480Gb SSD TRIM enabled.
HIS HD 7950 3Gb 5.0 GT/s EFI on mDP to DVI + DVI to DVI.
10.9.5 - 10.12.6  - 10.6.8 - Win 7 not Bootcamp. 
AREA 2 port USB 3.1 & Inateck USB 3.0 4 port in OS X 10.9.5.
h9826790
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« Reply #3 on: July 28, 2017, 06:26:32 AM »

You may test it in another way around. Put the card in slot 3 and see how it goes. That will make your card can only run at PCIe 1.1 x4. A measurable performance penalty is expected, but may not be that much.

IMO, unless the performance is really 300-400% difference. Otherwise, that means PCIe 1.1 x16 is already enough for the job. And further increase bandwidth won't give you any linear performance improvement.

In fact, I suspect those "huge improvement" exist because they are VRAM limiting. If all VRAM used up. The system now need to keep writing new data into the VRAM, which means more bandwidth helps. And double the bandwidth may really allow the job to finish in half time. If that's the bottleneck, FPS will be significantly improved.

It's not that hard to test this theory. Make 2 performance test in X-plane 10. One simple scene that require less than 1GB VRAM. And another one clearly can use up all VRAM. Run both in the x16 slot. And then run both in the X4 slot. Then compare their performance penalties.

If the theory is correct, the VRAM limiting test performance drop should be much higher than the non VRAM limiting one.
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