Critor has recently released a program that lets you clock your TI-Nspire to higher speeds than those chosen by the OSes. For now, certain programs such as Bwang's ray caster speed up the machine CPU at 150 MHz, while the normal speed is 90 MHz. However, the program had to go back to 90 MHz before exiting, because it caused problems with the TI-OS otherwise. However, after Ndless 2.0 developer source code was made compatible with OS 2.1, Critor ran some tests after compiling it to see how fast the TI-Nspire could run in TI-Nspire OS mode, depending of the OS installed and this were the results, posted on TI-BANK a few days ago:

OS 1.1-2.0 default speeds:
- Base frequency: 180 MHz
- CPU frequency: 90 MHz
- AHB bus frequency: 15 MHz

The max possible after using Nover:
- Base frequency: 180 MHz
- CPU frequency: 90 MHz
- AHB bus frequency: 45 MHz
 
This almost doubles the execution speed of TI-Nspire BASIC and OS functions.

However, OS 2.1 is different. Here are its default settings:
- Base frequency: 240 MHz
- CPU frequency: 120 MHz
- AHB bus frequency: 60 MHz

TI made that OS compatible with faster speeds to accommodate the OS's slower execution speed. At this configuration, the OS appears to run slightly faster. The removal of the limitation, however, allows critor's program to set the speed of the TI-OS even faster than in 2.0.1 or lower, though:
- Base frequency: 300 MHz
- CPU frequency: 150 MHz
- AHB bus frequency: 75 MHz

In other words, this would be between twice and three times faster than OS 2.0 running without Nover's support! However, remember that OS 2.1 has some downsides, such as its larger file size (although this can be solved with a previous program we posted news about) and your machine needs Boot2 1.4, not 1.1, else OS 2.1 will not start-up on it. In other words, if your TI-Nspire came with OS 1.1, make sure to install OS 1.4 through 2.0.1 on it and start it at least once prior installing OS 2.1!

Anyway, if you want to try the program, you can download it here! Be careful to which settings you choose, though, especially on older OSes, else, use it at your own risk!

Source (in French):
-http://ti.bank.free.fr/index.php?mod=news&ac=commentaires&id=919
-http://ti.bank.free.fr/index.php?mod=news&ac=commentaires&id=914

Discussion about Nover in english:
-http://ourl.ca/8530

^This. I wonder if OS 2.1 takes more battery power? I remember TI advertising that 1.7 took less power, but then I read it ran at the same speed as the older ones... but now OS 2.1 runs faster...

Thank you for the news. ^^

TI made that OS compatible with faster speeds to accommodate the OS's slower execution speed. At this configuration, the OS appears to run slightly faster. The removal of the limitation, however, allows critor's program to set the speed of the TI-OS even faster than in 2.0.1 or lower, though:
- Base frequency: 300 MHz
- CPU frequency: 150 MHz
- AHB bus frequency: 75 MHz

BTW, the AHB frequency can even go up to 150 MHz, but critor noticed that there wasn't much of a speed difference with 75 MHz.

I think I have an idea why there is no speed difference. IIRC, the AHB is used by the CPU to exchange data with other hardware components. If the components themselves are slower than the AHB frequency, then increasing it won't change anything.

Does this means that the OS can actually be clocked down to even slower speeds? That might be good for some programs that doesn't require much processing power.

Yes, you can downclock with Nover too, as I let you fully control all parameters values.

But don't downclock too much...
On all OSes (even 2.1), you get garbage over the display if some frequencies are too low.
I haven't tested very much (as I'm not interested in that), but it seems the Nspire screen doesn't like CPU frequencies of around 120MHz and lower.

He meant 120 MHz as the base frequency, not the CPU frequency.

You can't go over 300 MHz in base frequency...