Does loading an ActiveX control block page rendering?

I have an ActiveX control on a page I'm building (believe you me, I wish I didn't) using a static <object/> ta开发者_运维问答g in the page source (it's generated by the ASPx backend, but it arrives at the browser as part of the raw page markup).

Does Internet Explorer stop parsing and rendering to load the ActiveX controls as soon as it parses the <object/> tag or does the load happen in a parallel thread?

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ActiveX has to be loaded in the UI thread, otherwise most ActiveX won't work because they are STA. Same apply to IE's scripting objects some of them simply lack the proxy/stub for inter-thread marshalling, so DOM manuplation has to be in the UI thread too.

The parsing of the page could happen in the background thread.