user9865: 
I bought this Arduino clone over eBay. It seems to have an extra SPI and serial ports. How do I use these?

user368: Those are not additional I2C and UART ports, those are additional connectors connected to the normal peripherals. They are used in exactly the same manner as the normal connector.

user9866: UNO means ATmega328. It has always only one serial and one I2C port regardless of how many connectors (or solder pads) it is hooked to. They are just parallel outputs to ATmega pins:

D0 - TX 
D1 - RX
A5 - SCL
A4 - SDA
Extra pads are just for user convenience, for easier wiring. 

9865: <p><img src="https://i.stack.imgur.com/AJKKC.jpg" alt="Clone"></p>

<p>I bought <a href="http://www.ebay.com/itm/ATmega328P-CH340G-UNO-R3-Development-Board-Free-USB-Cable-for-Arduino-TGSNUYS-/261844126901?ssPageName=ADME:X:RRIRTB:US:3160" rel="nofollow noreferrer">this</a> Arduino clone over eBay. It seems to have an extra SPI and serial ports. How do I use these?</p>
 368: <p>Those are not additional I<sup>2</sup>C and UART ports, those are additional connectors connected to the normal peripherals. They are used in exactly the same manner as the normal connector.</p>
 9866: <p>UNO means ATmega328. It has always only one serial and one I2C port regardless of how many connectors (or solder pads) it is hooked to. They are just parallel outputs to ATmega pins:
<code>
D0 - TX 
D1 - RX
A5 - SCL
A4 - SDA</code></p>

<p>Extra pads are just for user convenience, for easier wiring. </p>
