Are there two fundamentally different kinds of the new M1-based MacBook Pro?

Manderic wrote:

Is this just bugginess in the Apple website that cannot recognize when a given model (e.g. 512 GB) is or isn't available for pickup at a store? Or is there some subtle real difference between picking 512 GB directly vs. starting with 256 GB and changing it to have 512 GB?

On new releases there is a supply of stock units ready to ship locally— 24 hour delivery in the USA

One would be considered stock— and ready to ship

The other would be BTO (Built to Order) and would come off the line in China

You can order over the phone /get more insight—

Call Customer Support (800) MY–APPLE (800–692–7753)

<< If there really is any physical or functional difference between the two, I would really like to know about that. Thanks for any clarification! >>

They are fundamentally the same. You should order the one that best meets your needs in every way.

In fact, they are likely even more the same than most users realize. When manufacturers build custom chips, they tend to build ONE Integrated Circuit assembly, and select-at-test for faster/slower more-capable/less-capable devices, which will get different part numbers screened on the top when they are packaged.

In this case, there is likely to be ONE M1 chip coming off the IC production line. That chip will be tested while still on the wafer for its capabilities, and customized for use in different devices. If one has a dust-spec in its 16 GB RAM array, Apple likely has a way of shutting off the bad half to make an 8GB part. If it has a dust spec in one GPU core, Apple likely has a way of disabling one GPU core. If it has additional defects or can not run at speed, it will be scrapped before it is packaged. IC yields are always FAR short of 100 percent good, fast parts.

Historically, the ways to customize have included using a laser to trim out certain critical connections to make a grand part into a petite part. It can also be done with slightly different connection signals to the finished, packaged part. For example, Intel used to sell much cheaper half-sized RAM chips which were marked A0-L, meaning that address line Zero was to be held low, to bypass the dead half of the array inside.

This improves yields substantially, but may mean Apple has to "hobble" perfectly good full-capability parts to make them act like the low-end parts. Later in the production process, yields often shift toward the "perfect" parts, so this may not be a wide-spread problem yet, but it may be eventually.

<< Why have two options when they are really the same thing? >>

That is a largely question of Marketing and Psychology.

People like to have basic models that are simple to order, and not overwhelmingly complex. So the marketing department decides what is a basic model, predicting popularity and pricing those models expecting that many people will order a basic model with NO options. The basic models are what will be produced in large quantities to have in stock on opening day, and possibly more along the way to have as store stock.

Then if a buyer wants something else, they can add it as an option to an existing basic model. In many cases, that unit will be built to order on the Just-in-time manufacturing line, and shipped directly when completed.