Agreeing with Gigabitethernet.
I just want to point out that the processor speed in a modem has nothing to do with the dsl link throughout. Higher effective dsl link throughput speeds reported as ‘sync rates’ are determined by two things: Firstly, there is the possibility of putting more bits in each ‘symbol’ sent (more ‘detail’, if you like), that is a greater number of possible values that each transmitted symbol can have. Surprisingly, however, the symbol rate is always the same: 4312.5 symbols are sent per second. Secondly, higher speeds are achieved by having less additional baggage included in with the transmitted data in the form of redundant extra error correction information added. If the line is bad, then this extra information has to be included in order to allow errors to be corrected by mathematically back-calculating what the true values sent were. This extra info slows things down as it leaves less room for real user data.
A sending modem sends stuff at a certain rate which is fixed and is not determined by how fast a processor can go. A sender uses hardware that cranks the data out at a certain rate and the receiver has hardware that decodes the incoming signal at that same rate which is always fixed, and the hardware is designed to pick up incoming stuff at that fixed rate. It’s no more difficult for a receiver or sender to handle a supposedly ‘fast’ line, because the actual symbol rate is always the same at 4312.5 symbols per second.
If you did base n arithmetic at school, think of base 2, or base 3, base 8, base 10, base 16, or base 60 etc. The higher the base the more information is packed into each digit or ‘symbol’. This is the first part of the thing that governs effective speed as mentioned earlier.
If your line is hissy, or it does not carry high frequencies well, then the number of bits put into each symbol (number of possible values, the ‘base’) will have to be reduced so that a received symbols can be recognised reliably. There may be various kinds of disturbances on the link, aside from the signal just not propagating to the far end or not being audible against the noise background. Examples are burst noise, interference and crosstalk. To help deal with these problems then added error correction info will be needed and this wasteful extra info will reduce the real user data rate.
Apologies if you knew all of that already.
Aside from the modem side of things, routers and firewalls may have trouble processing large numbers of packets per second though, because they have to perform checks on each packet, or make changes to packets, if they are acting as firewalls, or when they are performing basic routing functions involving working out which link a packet should be redirected to. A router or firewall may be asked to do more or less work per packet depending on how it is configured. If the transmitted packets are very short, this could mean a lot of packets per second and then this could mean that a router might need a better cpu to keep up. This is all about how many packets per second are sent down the link and what the router is being asked to do though, nothing to do with faster or slower links at the modem or dsl level.