Why does sv_maxspeed have a legal value ?

Just wondering...
Players speed is set by weapon type, so sv_maxspeed could be set to any value above 260 which is the max speed a player will ever be set on without plugin.
change it's value would allow to unblock sv_spectatormaxspeed (320 is slow when you spec in free view)

From http://scripting.elxdraco.net/cvarlist/ :

Sets the maximum speed. In CS it doesn't change anything after 260, because of the weapon's speed(You go faster with scout, which is 260)

Yes it`s true.

In HLSDK physics code HL/CS choose minimal value between weaponSpeed and sv_maxspeed value

pmove->maxspeed = min( pmove->clientmaxspeed, pmove->maxspeed );
//where clientmaxspeed - speed from CBasePlayer::ResetMaxSpeed (or VIP speed 227.0 or Weapon Speed or 240.0 speed if no weapons etc (last not possible in CS without additional plugins or special maps) )
//and maxspeed - sv_maxspeed cvar

But to unlock fast moving in spectator free view, you need to set (for example):
sv_maxpseed 9000
sv_spectatormaxspeed 9000
but it`s not all, it`s only server speed, and client speed cuted at 400 by cl_forwardspeed cl_sidespeed cl_backspeed cl_upspeed cvars. But those cvars have only one legal value - 400.0 changing it (for example) to 500 (all of them) will lead to advantage...

Yes, look into CL_CreateMove (input.cpp) HLSDK

In HL/CS player movement when you press the key, hold it and release is different.

KeyStates:
0.25 if a key was pressed and released during the frame,
0.5 if it was pressed and held
0 if held then released
1.0 if held for the entire time

And move parameters calculated like:
sidemove_maxpseed = cl_sidespeed * KeyState(of Right button) - cl_sidespeed * KeyState (of left button); then capped at weapon maxspeed.

So when we press D key its like:
sidemove_maxpseed = 400 * 0.5 - 400 * 0.0 = 200
so actually in that one frame our sidemove maxspeed would be 200 and not ~250 as weapons maxspeed
Let`s change 400 value to 600 (for example)
sidemove_maxpseed = 600 * 0.5 - 600 * 0.0 = 300 -> then capped to weapon_maxspeed ~> 250 value

Same with forwardmove_maxspeed and upmove_maxpseed.

So, if our cl_XXXspeed would be changed to greater equal values, we have advantage while pressing and changing the buttons. It`s not much, coz that effect only in one frame. But in 32+ strafe LongJump we have bad effect from it, and our distance would be lesser compared to 16+ strafe longjump.

Also exists bad keyboards, they can`t hold WD WA buttons together, its working like holding one button, and second pressing/releasing during frame several times. As i wrote our coefficient for pressing/releasing would be 0.25 instead of 1.0. And such players in some moments have advantage, and in some disadvantage.