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Comment by supernova87a | Hacker News Reader

I wonder, is the 8GB vs. 16GB "unified memory" the kind of thing where all of the hardware actually has 16GB, but they disable half of it to sell the lower price version? Like Tesla's Model S 40 kwh?

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Probably binning where faulty memory gets disabled and flagged as a 8GB chip?

Intel did that for the 486SX processor 30 years ago. The 486 was the first x86 CPU with an integrated FPU. Chips that failed the FPU test were sold as cheaper 486SX with the FPU disabled.

I've never heard that the 486SX was a binned 486 - my impression was that it was a deliberate choice done during manufacture. Wikipedia backs up my recollection: https://en.wikipedia.org/wiki/Intel_80486SX

Yeah, seems like “SX is a binned faulty DX” was a popular but unconfirmed rumor that has stuck with me for 30 years.

The die is the same, but there’s no evidence Intel rebranded rejected DX chips. Here’s an extremely pedantic discussion (when it comes to obsolete hardware, the best kind of discussion) on the topic:

http://www.os2museum.com/wp/lies-damn-lies-and-wikipedia/

That's not the only way they "bin" things. some have one time blow fuses and they will disable parts of the chip if they are being "lean" and just manufacture towards the number they expect to sell of each version. . It costs about as much to make one with an FPU or without it from a chip manufacturing point of view.

The unified memory used to mean that the ram is shared with the graphics card so you have not all available for your use. Also called shared memory.

Very excited for the tear downs of these to understand that as well. Could just be a binning thing as well if there’s faults in the memory.

Curious about the same thing, re: the 7-core GPU vs. the 8-core GPU on the Air. Seems like a pretty arbitrary upgrade (and only a $50 difference).

As with Pavlov's comment about the memory this could be a yield thing. It may be that there are enough dies where one of the cores fails that it's worth turning them into a lower spec model as happened with the 486 SX all those years ago. More than one core failing might not happen often enough to warrant making them a product line.

Lots of people talking about frequency binning and Benning in general. I would like to add in here someplace that AMD used to make 100% identical chips for an entire full lineup and then adjust the frequency and prices to the actual binning process like if they tested a bunch of chips and got a lot that did 3.8 then they sold them all as 3.8 if they did 4.1 they sold them as 4.1 it was quite common to buy the lowest possible cheapest AMD chip and get one that could essentially be and overclock to their number one highest bench chip. See fx 8120 the lowest bulldozer chip overclocking to be and identical performer to the much more expensive and higher chips.

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