The description for buying commlink upgrades on page 240 is kinda vague. So here's my example/question:

Let's say I bought a stock commlink with a Response of 1. I want to upgrade it to a response of 3. Can I just buy it right at rating 3 for only 1,250 nuyen? Or do I have to drop 750 nuyen for an upgrade to Response 2 first, before I can move on to Response 3?

I see no reason for requiring a linear progression. You're just swapping out cards/chips.

you just pay 1250

and for the record, you don't have to start with a commlink as long as you buy all the components.

I agree. You pay for response 3 and swap out the chips. The savvy player will now notice upgrading a MetaLink with Vector Xim is, thus, more affordable than doing the same to the Caliban with Novatech Navi (or what ever the highest OS is).

Exactly why I house rule the incremental upgrade. Or perhaps a better rule would be: You can only improve a Commlink attribute by 50%.

In realty, if I take a old busted-down comp and decide to ramp it up to killer levels, there's only so much I do with the existing parts. Eventually, I'm going to be replacing basically everything and there will be nothing left of the original computer, except maybe the case.

I suppose it depends on what you assume you're getting when you buy those upgrades. Is a Response increase just another "RAM chip", or is it a whole new motherboard RAM-bus add-on pack? I think that's up to individual GM's.

Remember, don't fall into the trap of trying to compare SR to real life ... repeat to yourself: "It's just a game" and all will be better

I suppose you could go for a retro kinda thing too. Crappy outer casing of some lower brand item, so that security doesn't get freaked out you're walking into their area with a top of the line model.

That would actually make you ultra cool at the hacker club in On The Run.

The way I run my game is that you still need to buy at least a basic commlink.

Upgrades are one thing, but unless you intend to build it completely from the ground up (making your own case, purchasing accessories and coding your own OS) you'll need the skills to do so... and perhapse some additional cost of the supplies and time it took to do the work. (will require proper contacts depending on upgrades)

For those who nit-pick about how you can only upgrade a system so far, this is the take on what a commlink is in comparing it with notebook/pda technology today.

Response: This is your mainboard unit. With microtechnology at this point, it's cheaper to just replace the CPU, RAM and mainboard with one convenient component for no-nonsense upgrades. The response does not include the case or basic peripherals that you would see on a commercial unit. The basic case and perepherals and parts still need to be purchased seperately if the hacker were to create their own Response boards.

Signal: This is your Wi-Fi/Cell modem. Better the modem, better the reception. Upgrades can only be purchased unless the Hacker has their own tools and parts and perform the proper tests to create it.

System: This is your OS and hard drive. Upgrades are available for purchase or online, or with the proper skills and tools, one can join an open source forum and upgrade their own OS. Without purchasing a base OS you will need to have the software skills, parts and tools, performed tests and cover living expenses in the time it takes you to code the software. You also will not get any basic programs, as those only come bundled with a commercial OS. Basic programs are at the rating of their commercial OS and will have to be purchased if they are to be upgraded.

Firewall: Mostly software driven, this small sim-chip keeps people from hacking your link. Still requires a basic commercial firewall or else you need the skills and tools to create your own.

This is probably more micromanaging than more GMs will want to bother with, but as a computer tech, I tend to be picky about such things

My thought on the "Commlink Upgrade" question is this: if indeed all you need to do is purchase the "end upgrade" (desired level), even if you need to buy the basic 'Link first, then an upgraded 'Link is astronomically (roughly a tenth) cheaper than the "equivalent" cyberdeck in SR3. So, as I see it, there are 3 ways to "fix" this problem:
1) Force upgrades to be incremental. ie. Rating 3 must be purchased before Rating 4 etc.
2) Limit upgrades to 50% of the base rating. ie. The Commlink must be at least Rating 4 to upgrade to Rating 6 anything.
3) Increase the cost and availability ratings of all the Commlink upgrades. Personally, to put things somewhat on par with SR3, I think a starting Hacker should spend about 100k to get a "fully loaded" Rating 4 Commlink (all attribs 4, and every program at 4).

As a GM, if you don't implement any of these "fixes" then remember that any NPC that has any data worth protecting will have a fairly highly rated Commlink. If a PC balks at this, remind them how much cheap their own Commlink upgrades were.