555
I don't think they will try to run from you, so no concerns about their speed.
There are no "ports" on a Pentium processor.
The Dell Precision 410 workstation was equipped with either a Pentium II or a Pentium III processor, at a speed between 350 and 700 MHz.
Nobody, since there is no Pentium 5 processor.
No Intel Pentium 4 processor was ever manufactured running at a clock speed of 500MHz. However, the previous product line, the Pentium III, had several variants running at that clock speed.
There is no "Pentium R" processor. Knowing this, the biggest difference is that the Pentium III exists and the other does not.
There is none. The Pentium D is based upon an older architecture and is slower, at any speed, than any Core 2 Duo processor.
The first Pentium processors (Pentium 60 - 66). A Pentium OverDrive processor is also available for it.
A Pentium 4 processor, and a motherboard that supports it.
pentium mmx
The Latitude D610 uses an Intel Pentium M processor, and the highest speed Pentium M Processor that is officially supported by the D610 published specifications is the Pentium M Processor 770 (2.13GHz) I know of reports of the Pentium M Processor 780 (2.26Ghz) being used, but I have not personally verified these. As of my last check with Dell directly, the 770 was the highest processor officially supported. An unsupported processor means no real assistance from Dell if you're having problems.
Probably the Pentium Dual-Core, as it is the most recent processor to bear the Pentium name.