I think they designed them differently because they were affraid some crafty guitarist/hacker would crack a 300/400 and get a 500 for half the cost. Frankly, I think they shot themselves in the foot there, because it's my experience that most guitarists aren't that tech-savy. It's like DRM (anti piracy software) built-in to the unit.  But if I had to think of a reason that would be it; if a 300 was basically a 500 with fewer buttons and some software-locked features, then they would be worried that someone would crack it and unlock the software-locks, and the majority of the public would just buy the cheaper 300 and learn to live with a few less footswitches since that would be the only difference.

Upside is if they made different hardware with also different software they have virtually eliminated the possibility of people "pirating" a 500 level processor out of a 300. Downside is they have to program for at least 3 different platforms. I'm guessing the cost and time they need to develop for all these seperate units is offset by hard-to-crack units; people buy what they need/can afford, as opposed to the cheapest and crack it.

This is of course just a theory of mine, but if they have an alterior one to what I've proposed here, I'd like to hear it because I can't see another reason for making so much more work for themselves and agitaiton for their customers.

Nah, it won't be the same architecture internally across the models.  Otherwise, why the staggering of firmware release dates? 

They would have built the original firmware for v2.0 (HD500+ version) and then there would have been a meeting (Title:  "what do we give the 400 users") that went along the lines of ...

"Do they get the Plexi ....?"

     "Hmmm ..... yeah, ok"

"... Cab Deps ..."

     "eeeeh .....  Nah."

etc.  Then a hash table in the firmware would have flags that enabled/disabled the features and that would have been that.  Simples. 

Different hardware.

Then why does it take weeks/months to get updates out? Why are they so staggeringly staggered? Obviously it's not for the enjoyment of the community, because the majority go apesh*t over the waiting. They've got to have a different hardware/software setup for the different teirs, because if they don't, well, then they're just a bunch of d*cks for making people wait unnecessarily. Are you calling Line 6 a bunch of d*cks Phil? lol

I'm not sure how you got that I was saying anything negative about Line 6 from that...

The system architecture of the 300 and 400 is pretty different than the rest of the HD line, and I believe that the development of the firmware for these units is done a bit differently from the others. It's not simply a matter of developing a model and plugging it into the firmware. As far as I know, each platform requires some unique coding. I don't think the reason for this has anything to do with Line 6 being worried about people "cracking" the devices though.

I would assume that is correct - while the basic signal processing algorithms need to produce identical output, they must be differentiated to do so for different architectures, in how they manage reading/writing to cache and other memory, and be able to do so in real-time given different DSP resources.

These differentiations may seem simple, but these are complex programs, and a seemingly-inoccuous change must be tested thoroughly to ensure no unexpected and possibly detrimental bugs are present, such as causing the device to reboot, or delete all patches, etc.

Back to the hardware differences; if they weren't worried about pirates, then such differing firmware software/hardware? Why not just put a 500 in a 300 encloser and software lock what they don't want people to use? I doubt if you gutted a 300 and a 500 they would extrememly different in manufacturing costs due to composition; I'm sure I'll be corrected quickly if I'm wrong, but I presume they're not made in the US of A, so manufacturing cost differentials probably aren't that significant. I'm tellin' ya; they didn't want anyone muckin' about in their floorboards, so they made it virtually impossible to crack the units for significantly more functionality.

They don't trust the userbase not to pirate/crack their hardware if they had one unified architecture. Plain and simple, anything software based can and will be cracked, so they went hardware/software variants. You want unilateral firmware releases, then fix the depravity of the human soul, and Line 6 won't have to build in anti-pirate measures into their hardware.

SInce everyone is guessing here, my guess is the consdieration about piracy played Zero roll in the design of 300/400/500. The most consideration was given to making available to the masses (the biggest target market possible), a cost effective solution to adopt the new HD modeling. Knob count, spdif connection, input impedence capability etc. were the primary factors in the decision to make the HD300 the entry level unit. At the price of the HD300, it must have been decided that to keep the price down you must have different hardware enough to cause the staggering updates situation. Of course they can't satisfy everyone, but the majority of those who buy the HD300 are very appreciative of having access to this advancement in modeling at this basement price.

It's not just a matter of marketing, it's also about sound and feel. There's simply no competition at the price range of any of the HD series models. the only problemetic competition is from the HD models amongst themselves. I intially bought the HD300 knowing very well that to get this kind of modeling and feel, I would have to buy ELeven or AXE at more than double or triple the price!! I've tried and researched almost evertything outthere and couldn't find anything remotely close at the price. Furthermore, at this price range, simply there are zero updates from all other companies. Many line 6 users are aware of this and are very appreciative.  few users complain and that's expected because it's impossible to satisfy everyone.  Also at these prices, cracking is the furthest thing from anyone's mind. Even at $100 model packs, I highly doubt that a sane person would consider running a crack even if it existed and risk damaging the hardware! Cracking is completely irrelevant to this subject in my opinion, because people have already bought the hardware/sofware package what's there to crack. When we get to AMP Farm HD , that can be a consideration, still at the prices that line 6 sell their software, i doubt that a serious guitarist/hobyis would even bother with cracks to use in their HDs even if it somehow did exist! Who's cracking their multifx?I haven't heard of cracks being a problem for Digitech prodcuts, Line 6 products, VOX, Eleven and when you use these hardware units with your PC or MAC they already provide the most sofisticated dongle there is that would mitigate 99% of cracks concern!