<p>Depending on what you are doing, it might take a lot longer. I had 20x speedups be using a GPU. If you read some Computer Vision papers, they train their networks on ImageNet for about 1-2 weeks. Now imagine if that took 20x longer...</p>

<p>Having said that: There are much simpler tasks. For example, for my <a href="https://arxiv.org/abs/1701.08380" rel="nofollow noreferrer">HASY dataset</a> you can train a reasonable network without a GPU in probably 3 hours. Similar small datasets are MNIST, CIFAR-10, CIFAR-100.</p>
Why do we need GPU for Deep Learning?
<p>As the question already suggests, I am new to deep learning. I know that the learning process of the model will be slow without GPU. If I am willing to wait, Will it be OK if i use CPU only ?  </p>