Sunday, March 07, 2004
What is the difference between OHCI and UHCI controllers?
Answer One:
What is the difference between OHCI and UHCI controllers?
In brief:
OHCI is made by Microsoft and emphasizes the fact that hardware should be smart to facilitate the software's task.
UHCI is made by Intel and stupid, in order to facilitate a low gate count.
Bottom line, OHCI has some brains and is actually able to transfer 8kb transfers in one go. UHCI needs to be told every single thing about a transfer: transfer descriptors, size of transfers, but also the sequence in which iso, interrupt, bulk and control transfers need to be done. It also means that the amount of overhead on the PCI bus on OHCI should be lower, allthough I have not measured that yet. OHCI is being used in firewire as well I believe. UHCI is simply to slow for that.
Answer Two:
OHCI: Open Host Controller Interface.
UHCI: Universal Host Controller Interface
UHCI and OHCI are types of USB host controller. According to our understanding, the difference between these two controller types is in the bus traffic scheduling timing. OHCI has stricter requirements regarding the timing at which devices are accessed.
Macintosh computers use OHCI, but there are some Windows PCs that use OHCI as well. Microsoft prepares drivers for both OHCI and UHCI for use with Windows.
What is the difference between OHCI and UHCI controllers?
In brief:
OHCI is made by Microsoft and emphasizes the fact that hardware should be smart to facilitate the software's task.
UHCI is made by Intel and stupid, in order to facilitate a low gate count.
Bottom line, OHCI has some brains and is actually able to transfer 8kb transfers in one go. UHCI needs to be told every single thing about a transfer: transfer descriptors, size of transfers, but also the sequence in which iso, interrupt, bulk and control transfers need to be done. It also means that the amount of overhead on the PCI bus on OHCI should be lower, allthough I have not measured that yet. OHCI is being used in firewire as well I believe. UHCI is simply to slow for that.
Answer Two:
OHCI: Open Host Controller Interface.
UHCI: Universal Host Controller Interface
UHCI and OHCI are types of USB host controller. According to our understanding, the difference between these two controller types is in the bus traffic scheduling timing. OHCI has stricter requirements regarding the timing at which devices are accessed.
Macintosh computers use OHCI, but there are some Windows PCs that use OHCI as well. Microsoft prepares drivers for both OHCI and UHCI for use with Windows.
