I am using a Prolific USB-to-Serial adapter based on the Prolific chip to use with a device on serial port. I have the latest version of the driver installed: 1.3.0 (2010-7-15).
When I use my device with this adapter on my main Windows 7 (32bit) system it takes 8-9 seconds to send a command through to the device. However, when I do the same thing on a different Windows XP system (an old laptop I borrowed for testing) it only takes 2-3 seconds. I have made sure that the port settings and other variables are the same between systems. I also tested on a third laptop (also running Windows 7) and again got a significant delay.
So the question is if anyone else experienced the same problem and found a solution. I would like to avoid moving to an XP system for what I need to achieve so that's my last option.