I know this was a few months ago, but searching and searching the net and this post is the only one that really had the same problems as you did. I did however find a solution.
The Anet A8 and its variants(like the Sainsmart A8) do in fact use a Arduino clone. Yes you are correct, it isn't a "true" Arduino. It is also a dedicated motherboard using an Atmega1284P processor running at 16 MHz.
I looked at my device manager which stated com 3 was showing as a Matter Control "RAMPS" board, whicg isn't right because I remember working on a few other A8's and they all used the CH340 drivers for the motherboard.
I then remembered the Arduino software is used to upgrade firmware which I forgot to install on this current PC and after reading post after post of the net someone said it might be the solution...…..
so I downloaded it and all the drivers that came with it (I felt stupid at this point, noob mistake) and Alas, no luck. Even the Serial Monitor as stated(in this discussion) would return anything but question marks.
At this point I went and got the board info from the Arduio software. It was shown as an "unknown" board, but HA! I have the VID and the PID. VID represents a manufacture, while the PID represents the model of the chip:
So I searched Bing(yes, I use Bing sometimes) and found these links:
Tried the first link: https://www.drivermax.com/USB-SERIAL-CH340-wch_cn-USB-VID-1A86-PID-7523-3_4_2014_08-2014-08-08-12053-driver.htm<br/><br/>Downloaded the drivers:<strike></strike>
Choose "only download this driver":
Scanned the download a few times to make sure it isn't bad and Eureka! It worked. The printer shows as " CH340 Controller" in the device manger. Arduino software and the serial monitor read it perfectly. Repetier host and server see it just fine. Prints come out just fine. I can even upload stuff to the SD card. Print off of it. The manual controls are instant. Everything. Now I can even upgrade firmware if I want ;). Hope this helps.