When you have a duplex mismatch between a server and  a switch or a workstation and a switch you will only see problems in either the upload or the download, but not both. This table shows where you will see the extreme network latency when there is a duplex mismatch.

PCSwitch-PCSwitch-ServerServer       UploadDownload
Full Full Full Full   Fast Fast
Full Full Half Full   Slow Fast
Full Full Full Half   Fast Slow
Full Half Full Full   Fast Slow
Half Full Full Full   Slow Fast
Full Full Half Half   Fast Fast