Will a i5-4200m bottleneck a gtx 870m?

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For ~$150 the upgrade to the i7-4810MQ seems like a good deal. Clockspeed increases from 2.5 GHz / 3.1GHz to 2.8GHz / 3.8GHz and you get 2 additional cores / 4 additional threads.

For a laptop the i5-4200m is definitely considered enough to play games with. Naturally, the concern is performance in games that can make use of more than 2 cores. If that is your primary concern, then I would say the extra $150 should be worth it.
For ~$150 the upgrade to the i7-4810MQ seems like a good deal. Clockspeed increases from 2.5 GHz / 3.1GHz to 2.8GHz / 3.8GHz and you get 2 additional cores / 4 additional threads.

For a laptop the i5-4200m is definitely considered enough to play games with. Naturally, the concern is performance in games that can make use of more than 2 cores. If that is your primary concern, then I would say the extra $150 should be worth it.
 
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