I'm building a nexus for an SR4 game and have run into a bit of a problem. What exactly determines the Processor Limit and Persona Limit for a nexus?
SR4A says Processor limit is System x 3 (pg 223) but Unwired says that formula is for Persona Limit while Processor Limit is anything from 10 to 50 (pg 50) with no indication of what determines that number. Should those have been reversed?

I'm gonna guess no one knows then. Time to make up my own rule and go with what makes sense.

Personally I've always gone with Unwired being correct, meaning Personas = System x 3 and Processor Limit as you decide between 10-50.

Does that make sense though? Which is more likely, that a nexus would need to be able to run between 10 and 50 programs or between 10 and 50 personas? Personally, I think it's the later rather than the former. Persona load is what a nexus is built for, not serving up dozens and dozens of programs.

I think I see where the confusion is coming from.

Nexi are by definition (unwired page 50) high performance mainframes designed to run a larger number of programs than standard nodes, thus the reason why they have a higher processor limit, allowing for more active programs because that's what they are meant to do.

The persona limit is not about inbound persona in any case, who are popping through to poke around in the electronic guts of the nexus, but rather about how many people can use the nexus to project a persona out onto the matrix.
Your commlink for example can only handle one persona at a time accessing the Matrix from it, while a Nexus can handle multiple peoples going online through it.
Again, it does not count persona running from/originating from another node that happen to be accessing this nexi.
The virtual 'burden' of the incoming persona is on the originating node they used to enter the Matrix with.

Plus multiple nexi can be clustered to combine their persona and processor limits into nodes with astronomical numbers of personas and subscriptions.

So it may seem odd, but that's because in the end nexi were designed differently than regular nodes.

No, there isn't any confusion on my part. I know exactly what they are for but there is a conflict between what the core book says is their Processor limit and what Unwired says it is. The core book formula follows the same formula as commlinks (System x some number) while Unwired makes it some random number between 10 and 50. My gut tells me to follow what the core book says rather than Unwired, especially since it seems more logical that a nexus would potentially need to support up to 50 personas than it would up to 50 programs.

Conflicts between books within the same edition? *GASP*

Yeah, there is never good answer to that one....

I personally don't see a problem with increasing your persona limit for something like a nexus if you want, justifying it as a major login point type of node, except if you are going to have 50 personas on there, you are going to need to increase the processor limit well past 50 anyway, otherwise you are just going to rack up serious Response degradation unless everyone is just going to use one program each at a time.

Granted there are a lot of actions they can be taking without needing a program, but it can still add up should everyone jump in.

So a public nexus could be like that, a matrix café might be high persona limit/low processor limit because most everyone there is just checking social media/news blogs or chatting up someone.
So while everyone can get on, response time becomes abysmal if even a few people start doing some program action there.

This encourages one to get onto something better, subscribing to a better nexus which has medium to high persona limit AND a corresponding high processor limit so everyone can enjoy their research/hacking/multitasking without worrying about being bogged down.

So maybe just figure out whatever formula you want for persona limit and then slap on a processor limit multiplier depending on the type of nexus.

More Casual use style nexus like a café nexus would be from x 0.5 to x1 at most, again most people there are just casually flitting about with only a few persons really needing anything more program-y going on.
So if your Café could handle 30 personas logging on there, you could have a processor limit of 30 tops and maybe even lower if they skimped on the equipment budget.


Library/other research facility might be x2 - x3 as the various folk there might be doing several actions with creating, searching and editing files, etc...
So if the Library could handle 30 personas, they could also bear up to 90 programs running before slowing down.

Yeah, errors in a book, conflicting rules, I know, I'm just as shocked as you, especially as this is a Catalyst product. They are usually soooo careful about that sort of thing I do find it funny this error has existed for so long. Shows just how much people actual use or at least properly use nexi is SR4.

Anyway, I was looking over the way these things are supposed to work again. Lets see if we can sort out which is the more likely intention.
Case 1:
Low end Nexus (worst case scenario) Response 1, System 1. If SR4a is correct, then this nexus has a processor limit of 3 and could have anywhere from 10 to 50 personas running from it. Since each of those personas needs some sort of software, this seems unlikely.
If Unwired is correct then this nexus could have anywhere from 10 to 50 programs running on it and could support at most, 3 personas. This seems the more likely set up. With 10 programs, each persona could have 3 and with 50, each could have 16 programs, or more than they would ever need at once. The rest of the load could be IC or agents.

Case 2: Milspec Nexus (best in the world scenario) Response 10, System 10. Under SR4A this nexus has a processor limit of 30 and again, anywhere from 10 to 50 personas running from it. More feasible but again, not very likely. With a Persona limit of 10 you would each get 3 programs but it goes down quickly beyond that.
Under Unwired, it would support up to 30 personas and again have 10 to 50 programs running on it (OK if it really is high end, then it has 50). This also seems more likely but with the higher Persona load, it would need more programs available. If all 30 were active, they could have 1.6 programs each with no IC or agents or such. Seems odd for a high end server.

Case 3: Mid Range Nexus (best non-milspec) Response 6, System 6. With SR4A, it has a processor limit of 18 and 10 to 50 personas running here. Not really enough programs for even the low end of 10 personas.
With Unwired it would have a Persona limit of 18 and 10 to 50 programs. At the low end it can't run even 1 program for each persona and at the high end it can at most, run 2 programs per persona with the rest of the load taken by an agent or something. Better than the milspec server but still not as many programs as the cheapest nexus.

So it would seem Unwired makes more sense but it also falls apart once you get beyond the low end servers. Not enough program capacity to support all the personas available and also no room for the all important IC or agents.

I think neither of these formulas are ideal. Having to buy multiple nexi and slaving them together just to support a classroom for example, seems a bit much (Unwired route) but on the other hand, having support for a ton of personas but not having any software for them also doesn't work (SR4A route). It also seems weird that you would need a milspec nexus before you could support a classroom of 30 kids.

My initial assumption on programs was that the nexus could just serve these up to personas as needed but it seems (according to SR4A pg 232) that the persona stores the program, not the node (commlink, nexus, whatever). So under that rule, while the processor limit determines how many programs can be running on a nexus, those programs are actually stored on the personas or agents loaded on the nexus. However, for extra fun, Unwired says the opposite (pg 52), that the node stores and runs the software, not the persona. So that makes things just clear as mud.

Having the Persona limit set by system might work so long as Processor limit scales as the Persona load goes up. Setting Processor limit to System doesn't seem to work out too well, unless the Persona limit is tied to it somehow. Basically, either of these values has to be tied to the other. They can't be independent or else the nexus won't be able to serve its purpose.

I'm not sure I've arrived at any conclusion beyond that neither rule actually works.

Finally had a chance to look at my physical books, the German 4A only says: "Nexus [counterintuitively the correct plural] often are not subject to the Processor Limits of less powerful devices".

So I guess it is actually supposed to be "whatever the GM deems appropriate". Since those devices are mostly intended as "scenery" and not character gear, it makes some sense to leave it up the GM.

Nothing like that in the English version. Just says that System can be higher than Response except in the case of an agent or IC running on the nexus. So not only conflict between two rule books but also across languages. Fun.
I'm going to see if I can come up with something that works and makes me happy as far as scaling Processor limit with Persona limit.

If the purpose of the Nexus is to be able to run several personas on the same device, and if neither of the official rules actually work, why not houserule it so that you get a Processor Limit equal to System x number of Personas that can be run on the Nexus. That way you'll get something that scales with the number of Personas that can be run. Then there's the question of how much it should cost, but that's a different matter.

The German version is supposed to have errata, so I'd say the formula simply was a mistake introduce in 4A and fixed in the German printing.