The Machine Cortex covers three very important functions; competency, coordination, and personality. The capability of said cortex is the biggest limitation on synthetic intelligence.
In base terms Competency is composed of the skills, and knowledges possessed by the robot. This is the area where most cortices shine as it is relatively easy to fit large amounts of data into a machine brain. The amount of memory available to a machine is a minor issue, as the difficult and expensive components are those that actually process said data into a usable output.
One of the major hindrances in modern robotics is one that is conquered by children around the 12-18 month demographic, walking. Walking, acting, and physically doing things takes a large amount of processing and code. The higher the level of athletic ability or coordination required, the more dedication is required. Thus, a human can learn to ice skate relatively easily, but becoming a professional requires a serious commitment. A cortex with low coordination is going to be atrocious or completely incapable of this act, while a IceDancerDroid will have vast amounts of processing power devoted to it's execution of Olympic figure skating routines. It is a venue of competence that is easily overlooked because it is very rare that someone fails at walking, or grabs an object with the wrong amount of grip force, or otherwise screws up a coordination check.
And when it does happen, it's usually pretty funny.
Or a trip to the hospital.
The trait of personality is a construct of vocal patterns, idioms, internal priorities and biases, and modes of expression. The more human and lifelike a machine should be, the more processing power has to be diverted from other applications to the continuation of a running personality complex. Machines with very low personality scores are very robotic, monotone, and do not interact will with humans.
Balancing The Triangle
In the Cosmic Era it is completely possible to create a cortex of sufficient complexity and ability to emulate humans on a one to one level. The biggest problem with this is that said cortices are highly sophisticated and expensive. Thus, there are various shortcuts that cortex and robot manufacturers will take to use more economical cortices to make said robots affordable and workable for the average person or employer.
The most common fix for Competence is the CogNet link, with an online program assist. Much like a pokemon's ability to only know four moves, cortices with CogLinks have limited space devoted to skill memory, and will rotate through skills, dumping the least used or lowest rated skills in their repertoire and downloading or even streaming the ones that they need. This is a very common fix, as it can double for Personality Fix, streaming a persona or avatar through the machine without it ever having one of it's own. The downsides of this fix is that lacking CogNet access, the robot is effectively lobotomized, and being constantly connected leaves the machine vulnerable to hacking. While the most common fear is the rogue robot, the most common malware is voyeuristic and data mining, and can go years without ever being discovered.
The Cortex Expansion - being robots, it isn't hard to make the cortex of a machine expandable, and cortex expansions are dedicated modules. These allow for the development and growth of a machine intelligence over time, to match the finances and the needs of those using said robot.
Physical Limitations - robots without legs don't have to have coordination skills, which means machines like utili-pod and canister type robots can devote their cortices to their skill sets rather than wasting power walking. The same goes for stationary units like the pribnow dummy. The same applies to machines that do not emulate the human form. Faces and hands, gangling arms and legs take a large amount of processing to control.
Limited Expectations - Autons benefit from this fix, they totter about in a generally harmless and inefficient manner. No one expects them to walk or move like a person, so long as they can get too and from wherever they need to go and can complete their tasks in a nominal fashion. Likewise, many cortices designed for sexual or physical interaction will be noticeably dumb or will have very facade like personalities.
The Level of a cortex is functionally the maximum number of character creation points that can be put into it. In character attributes, the cortex is vital for dexterity (strength and stamina are functions of the chassis of the robot, not the cortex) Intelligence, Perception obviously, and the expression of the personality in terms of charisma. All talents, skills, and knowledges are contained in the cortex, and are likewise included in the points cap provided by the cortex level. Each level of cortex adds 10 points to its max capacity.
Most of the mechanics I have used behind the Cosmic Era are rooted in the D10 dice pool system used by White Wolf and the World of Darkness setting. A starting level character has 43 points to spend in character creation, and this would match a level 5 cortex, rounding up to 50 creation points, because thats an easier number to work with. The level 5 cortex is expensive, and most commercial, residential, and even military cortices are level 2-4 instead.
Shoestring Budget - the low level cortices are functional, but almost have to have a fix to keep them usable on a day to day basis. Building them is a constant trade off, and it is encouraged to take flaws for extra creation points, such as having the cortex only being capable of one task at a time, ala the robot literally couldn't walk and talk at the same time.
Higher level cortices are certainly available, on an increasing cost and decreasing availability scale. Access to a manufacturer, cyberneticist, or a clocksmith can make this easier, but likely not more affordable. It is also completely possible to fit a high end cortex in a low end chassis, and this is fairly common, making 'sleeper' robots. People working routinely with military employed droids have no idea how many of the machines they work with might have high end espionage and counterintelligence cortices, or how many might be rapid response counter strike units, disguised as secretaries or menials.
Examples of Cortices and Fixes
R2-D2 is a fantastic fix. The droid requires no coordination, as it is a rolling tripod and has very few moving locomotive parts. Likewise, personality is very low. Like a dog, the droid can make a number of vocalizations, but can only express itself in a series of machine noises. No face, no linguistics, no posture, no body language. All of the unit's cortical potential is tied into it's intellect and execution of skills and abilities. This means that it can use a Basic lv 4 cortex and still have the ability to chart hyperspace coordinates, execute repairs on the fly, and function as a back up pilot in a fighter.
C-3PO is also a fantastic fix. A tottering, physically incompetent, oblivious but neurotic mess of a droid, he executes functionally with a low level cortex. Personality is a facade, and the unit almost completely lacks empathy and ability to process human interactions, it can walk, but the most strenuous tasks it can handle are picking up small items, and scurrying. On the other hand, it has the ability to make rapid and accurate calculations, and very likely a maxed out linguistics skill.
A Little Horrorshow
The Cosmic Era wouldn't be complete without a little bit of psychological horror. A human brain can be sustained long term with little upkeep inside a machine shell. This isn't so much a cyborg as it is a machine stealing basic motor function from a semi-functional brain. This also means it is relatively easy to turn most any robot chassis into a cyborg platform. There is the potential for deception, thinking a relatively simple cortex and OS is another sentient being, or realizing that a menial might be a person who's body was stolen, chopped for parts, and their brain crammed in a can because they knew something useful.
The machine cortex differs from the sophisticated machines that are the Artificial Intelligence Super Computers (AISC) and AI/LAI systems found in mecha and other large machines. The cortex is designed to mimic humanity, as well as to fit inside a human sized machine. The LAI employed by mecha and variable fighters are much larger, and do not mimic humanity, nor they have space devoted to personas or human interaction beyond their missions and diagnostics. Likewise, AISCs are massive, filling entire rooms like 1950s computers. Their abilities are high enough that to try to chart them on a character sheet is pointless. That a dozen AISCs created and control the operational parameters of the CogNet in its entirety should be a good measure of their potential. C-3PO might now 6 million languages, but a single AISC devoted to linguistics knows all of the languages, and is introducing and modifying new ones to increase the effectiveness of communication.