My laptop uses an AMD A9-9420 at 3GHz. It has 4Gb RAM and 1 Tb of disc. I can play classic with no problem but when I try to play retail it is VERY slow and more often than not I get disconnected from the server. Anybody tell me why and suggest what I can do to improve matters?
TIA,
David
2 things, you are using HDD? also 4GB of ram is definetly too low for WoW.
4GB is low but still should not prevent the game from working, especially cause disconnects.
Absolute improvement would be to use better hardware. If the game works kind of fine at 720p mode 1 (very low settings) then it’s just game requirements. If it still disconnects then it may be some network issue as well.
Server probably got bored waiting for your computer to load things and figured you got disconnected. 
Seriously speaking that computer does not even meet the minimium requirements for WoW. For integrated GPUs like the one in APU required memory is also 8 GB rather than 4 GB.
Between slow CPU, lack of RAM and slow HDD I wouldnt’t be surprised if the connections problems in retail are caused by the poor performance, especially if Classic works without disconnections which seems to rule out network problems.
I never realised you can play WoW on what is basically… An abacus.
Hey Pebzpaw!
While Accelerated Processing Units (APUs) are great as an integrated solution, and useful for keeping laptops slim and portable while still able to run a good amount of graphical applications, they’re not quite up to the task of dedicated gaming just yet 
You can check our system requirements for WoW, but sadly APUs are generally unsupported for an array of reasons, the main being is they’re just not quite powerful enough to cope with modern WoW.
Your generalization is highly misleading and in the end - false. Ryzen APU is also an APU and can run the game fine. Pre-Ryzen APUs even though much weaker are technically supported (the game doesn’t show the standard “your graphics card driver is not compatible” as it does pre-DX11 GPUs and alike) - they support the proper DX versions, the CPUs have all the instruction sets. In edge case scenario they can be to weak to provide playable framerate though. People even put WoW on Intel tablet Atom SoC systems for the memes.
I have a A8-9600 desktop APU benchmark from patch ~8.1.5 and in Dazar’alor Great Seal entrance 1080p mode 7 it was up to 25 FPS avg and that’s only bit better than the mobile A9-9420 unless some restrictive cTDP is put on it. Ryzen 3 2200G APU reached bit above 40 FPS in that test.
Under 8.3.0.33941 mode 1 720p a lot of low spec chips managed to run the game fine as well - https://rk.edu.pl/en/benchmarking-world-warcraft-integrated-graphics/ not to mention that on macOS even 2014 mac Mini with i5-4260U can run the game on such low settings and even handle wiping on LFR N’zoth without stutter
How on earth do you have 4 gb ram but 1 Tb of disc
Top 10 questions science still can’t answer
Some cheap-end notebooks come with the RAM directly soldered on to the motherboard, and not expandable.
My guess is that this is the case here. That abacus came with soldered RAM, but he was able to increase the storage himself.