Are you talking about the ESXi video output, or that of a VM?
1. vSphere 5.5 goes End of Sale before the first 4K monitors comes to the market
2. I assume that you opened a KVM session of a VM by using the console of the vSphere Client*. A OS starts with normal VGA and 640x480 or 800x600 and start later switch to a higher resolution.
You should install VMware Tools to get better GFX and higher Screen Solutions together with Mouse support. Also dont use the Console for Day to Day work! You should use RDP or what ever the OS offer for remote control.
* If you dont use the tab console and open an external console windows wasnt there a AutoFit, Resize option?
Sometimes, I cannot make rdp connection to virtual machine as they have network card problem and I to use Console part of Virtual machine .
I really have problem with interface. also overlly VSphere client is very small and most of texts are not readable.
So mean you just update to new version 6.5 will solve problem ?
Windows vSphere Client was freeze in 5.1 or 5.5 and no new features where added. It goes deprecated than and vSphere 6.0 last version which can be used with the old vSphere Client. VMware replace the Client with the Browser.
ESXi direct = Host Client
The Host Client was introduced as a Fling and was an installable AddOn for 5.5 and early 6.0. Later ESXi ships directly with the Host Client
vCenter = Comes with the Web Client (Flash version) and was later replace by a pure HTML5 browser based Version. The HTML5 Client becomes the new vSphere Client.
So the console you used is now embeded within a Browser or as a small windows based helper Application named Remote Console. The Remote Console have some more features compared to the HTML Version like attaching a local CDROM/ISO for example.
Your are 5-7 years behind with your old 5.5.
There is no dpi syncing in 6.5 or 7.0 either in the HTML or remote client either from what I've seen, but its easy just to change it when you connect. If you have trouble seeing it just drop the resolution down to 1080p on your monitor and then increase the scaling in the VM to what you want like 200% or similar, then increase it again. Its something you can probably put a product request in for, I'm not sure vmware tools can do dpi syncing now, I'm pretty sure with horizon its done through the agent itself.
You might be right about the dpi scaling but if you use the WebConsole it automatically resized the console with your browser Window and my tiny linux login shell become VERY LARGE on my FullHD Display. This doesnt work with the Remote Console where every thing is very tiny.
Within the Webconsole also the page resizing works between 30-300%.
Remote Console in the upper left and WebConsole in a full screen browser session.