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VMEBridges
The CMS online sofware currently supports two PCI-to-VME bridges:
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The CAEN optical bridge. It consists of following modules:
- A2718 : The VME Controller.
- A2818 : The PCI card.
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The CAEN USB bridge. This module is software compatible with the
optical version. (ref. No. A1718).
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The SBS optical bridge (Model 620 or 618).
Why a PC-to-VME interface and not a Single board linux computer?
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It is cheaper to upgrade a PC than VME-board computer.
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All CMS online software is developed on Linux PCs.
We will profit from recent linux kernel developments and all available linux tools.
It is not so clear how a VME linux computer will be able to follow this rapid development.
Experience shows that on the VME single board computers in the end you always have pretty
old OSs, compilers, ... You also have to consider that the online software uses external
packages which are usually developed for standard PCs. Of course it is possible that all
this software will also work on such a VME-board PC but probably some of the packages
have to be ported by us which can be complicated and time consuming.
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The big Linux community will not care a lot if there is a problem with some VME-board computer.
So the company producing the board has to do all work which is special to that computer.
If after 5 years the hardware is obsolete, who knows how long they will continue to port
up-to-date kernels to their old systems. It will of course depend on some economical
considerations for the company, and not on the request of a client like us...
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