Sounds like you have a dual-processor 1.8, M9454LL/A from late 2004. It's not a dual-core machine, as you have individual processor modules, from what I can recall. You might look at this DV Warehouse listing for further information on a possible processor module.
A little concern remains about why Thermal Calibration failed, though. Do you recall what error codes were reported?
Thank you or your reply, old comm guy. Indeed it is the model that you refer to, I was just being mentally lazy and confused it with my laptop. Thank you for the link, at least i know that it is possible. For the sake of completeness I found this link for removing the processor unit
although from my perspective it seems to have started in the middle.
The thermal calibration results didn't report any code as far as i can remember, just that they failed and need replacement. At the moment I seem to have a happy single processer 1.8 that will be capable of doing the jobs I will give it and am reluctant to even put it in sleep mode not to mind restart it!