rMBP: entry level vs. top of the line

[iDutchman]

16GB was allowed with any CPU from day 1.

What wasn't allowed initially was a 2.3 with a 512GB SSD, or a 2.6/2.7 with a 256GB SSD.

Oh, you're right. That's what it was. I wanted the 512GB SSD.

 

[derbothaus]

Your objection and "correction" implies that the VRAM for an IGPU is segregated and not shared (and I'm pretty sure that's not true). What's the point in "shared" RAM if it is fixed capacity and not dynamic?

And as you can see here, I'm not making that up just because it's seems like common sense. Apparently it's fairly common knowledge.

There is no "VRAM" so to speak it is shared memory with the system running at the system memory speed. Which in terms of GPU's is pretty slow.
If you read through it the uninformed users on that thread finally get to the correct resolution. The memory on the integrated GPU's DO share with the rest of the system. They take their portion at boot. "Thanks for the 384MB" the rest of the system has the remaining portion to use accordingly. A 4GB system would then have 3712MB of memory for other purposes. If you have a system with 8GB installed the integrated GPU says "Thanks for the 384MB" the rest of the system now has 7808MB. The iGPU can't ask the system for 512MB of memory if it needs it. It does not work like that. On the dynamically switching Mac's (most recent Macbook Pro's) it may let the system recoup the used 384MB when using the dedicated GPU and then grab it's 384MB when switching back to the integrated, I don't exactly know but it would be a point of kernel panic if something were to go wrong with the switch over so it may just hold onto it indefinitely. Point is that the Intel 4000 is rated at 384MB "shared memory" with the system and will not use more if you add more memory to your Mac. Any feeling that it has a performance increase is placebo.

 

[terraphantm]

Oh, you're right. That's what it was. I wanted the 512GB SSD.

Same here - though I probably would've ended up getting the 2.6 anyway since it was only $100 more

 

[NewishMacGuy]

I think you are confused on something. "VRAM(GDDR5)" and normal "SDRAM DDR3" are two completely different and separate things. Your discrete GPU (in this case a 650m) VRAM is always 1GB no matter on which model you have.

All SDRAM does is allows you load more programs at once or allow one program to use more memory to preform functions. It literally has zero to do with the video processing on your computer. Now the IGPU and the discrete probably do share the VRAM but the number is still going to be the same between every single rMBP.

Your "common sense" and "fairly common knowledge" is completely wrong. I suggest, if you want to learn more about how a computer works, you stay away from the macrumor forums. I've been scanning this forum less than a week and I've come across more false information and nobody correcting it than the entire time I've been using internet forums.

VRAM is just the RAM that a GPU (any GPU) uses for its data processing chores. DGPUs have their own physical RAM, which you correctly point out is fixed and of a different standard than your SDRAM. However, it's my understanding that the Intel HD3000 and 4000 IGPUs "share" the main processor's physical RAM according to an algorithmic allocation. Is this not true?

Most IGPUs are allocated a fixed maximum amount, and apparently, in the 2011 and later macs (and possibly prior to that) the HD3000 (and probably HD4000) are allocated maximum RAM (to use as VRAM) on a dynamic basis. I do not believe that the HD3000 or 4000 share the VRAM from the DGPU in the cMBP-15 or the rMBP-15. They certainly don't in all the Macs which don't have DGPUs.

 

[scenox]

There are two other differences: HD 4000 clock speed is 1250 MHz instead of 1200 MHz and L3 cache is 8 MB instead of 6 MB.

And there is definitely more HD 4000 graphics memory allocated with more RAM.

 

[terraphantm]

There are two other differences: HD 4000 clock speed is 1250 MHz instead of 1200 MHz and L3 cache is 8 MB instead of 6 MB.

And there is definitely more HD 4000 graphics memory allocated with more RAM.

The maximum the HD4000 will be allotted is 512MB, which it does with 8GB. Upgrading to 16GB doesn't cause it to be bumped to 1GB

 

[kevink82]

Only the custom order 2.7 ghz cpu comes with 8mb cache, the rest of the cpu models only sports 6mb cache so that part of the info is wrong.....

http://www.anandtech.com/show/6023/the-nextgen-macbook-pro-with-retina-display-review/2

GPU clocks seems to be correct.

 

[ET3SW]

Wow. You're just making stuff up.
The IGPU has a set amount of memory allotted to it (Intel 4000 uses 384MB DDR3). It does not dip any deeper whether you have 4GB, 8GB, 16GB, 32GB, etc. It is what it is. It reserves what it is made to reserve. Memory speeds up nothing if you have enough of it to never swap to disk. Memory allow you to run further in a race not any faster. For that you need faster clocked (800MHz vs. 1333MHz) memory or newer generation of memory (ie. DDR2 vs DDR3).
All Intel 4000 IGPU's use 384MB VRAM. At least in all of Apple's portables. 13" cMBP, 15" cMBP, rMBP.

Actually that is not true. If there is 4gb of Ram installed it will use 384. If there is 8gb or more it will use 512mb

And that is true on the portables.

 

[terraphantm]

Wow. You're just making stuff up.
The IGPU has a set amount of memory allotted to it (Intel 4000 uses 384MB DDR3). It does not dip any deeper whether you have 4GB, 8GB, 16GB, 32GB, etc. It is what it is. It reserves what it is made to reserve. Memory speeds up nothing if you have enough of it to never swap to disk. Memory allow you to run further in a race not any faster. For that you need faster clocked (800MHz vs. 1333MHz) memory or newer generation of memory (ie. DDR2 vs DDR3).
All Intel 4000 IGPU's use 384MB VRAM. At least in all of Apple's portables. 13" cMBP, 15" cMBP, rMBP.

Note it says Intel HD4000 512MB

 

[derbothaus]

^^^Well look at that. My apologies. All the Intel documentation I had looked through had it rated at 384MB. I found the document from Apple answering all and it looks to bottom out at 512MB. So yes it appears to grab more at mathematical intervals but does not grow and shrink dynamically. And as stated by terraphantm it wont reach 1GB. However I have seen PC allotments reach 1024MB and then with only 4GB of system memory so I guess read carefully. Something I did not do.

http://support.apple.com/kb/HT3246?viewlocale=en_US&locale=en_US

Sorry for the confusion. I should have looked at my own Macbook that also states Intel 4000 512MB.