# R9 280X drops in Hashrate after 4 GPU's

**URL:** <https://forum.zcashcommunity.com/t/r9-280x-drops-in-hashrate-after-4-gpus/21090>\
**Category:** Mining Support\
**Created:** [September 2, 2017, 12:01pm UTC](https://forum.zcashcommunity.com/t/r9-280x-drops-in-hashrate-after-4-gpus/21090 "2017-09-02T12:01:37Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Justbitcoinz](https://avatars.discourse-cdn.com/v4/letter/j/c67d28/32.png) [@Justbitcoinz](https://forum.zcashcommunity.com/u/Justbitcoinz)\
**Post date:** [September 2, 2017, 12:01pm UTC](https://forum.zcashcommunity.com/t/r9-280x-drops-in-hashrate-after-4-gpus/21090/1 "2017-09-02T12:01:37Z")

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Hello fellow miners …

I saw the other thread but the answer is not answered.

I have 8 R9 280X cards and an Asrock H110 PRO BTC.

I have 2 power supplies with 1800 watt in total.

With 4 cards i gor about 1100 Sols and after putting in the 5th card i got 150 sols per card.

tried overclock but there is no change.

I use simpleminingOS because this setup with Windows is giving problems.

Who can help me.

Thanks in advance

Greetings Justbitcoinz

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**Author:** ![Justbitcoinz](https://avatars.discourse-cdn.com/v4/letter/j/c67d28/32.png) [@Justbitcoinz](https://forum.zcashcommunity.com/u/Justbitcoinz)\
**Post date:** [September 2, 2017, 1:35pm UTC](https://forum.zcashcommunity.com/t/r9-280x-drops-in-hashrate-after-4-gpus/21090/2 "2017-09-02T13:35:27Z")

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The cards went from 250 - 270 a card with 4 and 130 - 150 with one card more … Somebody know ?

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**Author:** ![fccs](https://avatars.discourse-cdn.com/v4/letter/f/73ab20/32.png) [@fccs](https://forum.zcashcommunity.com/u/fccs)\
**Post date:** [September 8, 2017, 3:42pm UTC](https://forum.zcashcommunity.com/t/r9-280x-drops-in-hashrate-after-4-gpus/21090/3 "2017-09-08T15:42:31Z")

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Are they all the same card or set to same clocks?

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**Author:** ![belgarion84](https://sea2.discourse-cdn.com/zcash/user_avatar/forum.zcashcommunity.com/belgarion84/32/10277_2.png) [@belgarion84](https://forum.zcashcommunity.com/u/belgarion84)\
**Post date:** [September 8, 2017, 3:46pm UTC](https://forum.zcashcommunity.com/t/r9-280x-drops-in-hashrate-after-4-gpus/21090/4 "2017-09-08T15:46:55Z")

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@Justbitcoinz

Can you detail what BIOS changes, if any, you have already made? My first suspicion is that you may need to adjust the PCI max speed to a lower generation setting, but I’d like to know what you’ve done already.