[Switched2Mac]

I see lots of people moaning about the new iBook ATI Radeon 9550 (and the older 9200) having only 32 meg of video ram.

Let's do some math!

The built-in display is 1024 x 768 pixels = 786,432 pixels required to generate the display.

And it is 32-bit color depth = 4 bytes of data per pixel to hold the color depth data.

So 786,432 pixels x 4 bytes/pixel = 3,145,728 bytes = 3,072 KBytes = 3.0 MBytes

So it takes only 3 megs of your precious 32 megs to actually display the screen.

I also happen to drive an external NEC MultiSync LCD1765 with my iBook using the spanning hack.

1280 x 1024 pixels = 1,310,720 pixels required to generate the display.

1,310,720 pixels x 4 bytes/pixel = 5,242,880 bytes = 5,120 KBytes = 5.0 MBytes

So to generate both displays at the same time, it only takes 8 megs of my 32 megs of video RAM.

Now most video card makers generally build the next image in memory and swap them into "live" video memory to speed things up. So they will have more than one 3 meg display buffer depending on the implementation.

32 megs of video RAM is more than enough for the iBook G4 series. This laptop will not handle Doom3 or Half-Life 2 or Battlefield 2, etc. So why bother pumping it up?

Once we start getting Intel dual-core Pentium M chips in the iBook, then you will be able to handle those CPU/GPU intensive games and apps. But for now, we'll have to wait....

[gametime10]

Very helpful...thanks

[Eug Wanker]

So it takes only 3 megs of your precious 32 megs to actually display the screen.

Incorrect. The memory usage for EVERY window on screen has be calculated separately, and added to the total.

For a single screen, 32 MB isn't great but OK for average usage. For dual screens, it's inadequate, since each screen gets only 16 MB.

IMO, all Macs from now on should have at least 64 MB GPU memory minimum.

[ghporter]

What Eug points out needs a little more detail. The SCREEN BUFFER really only takes 3MB, but each window is a separate entity that exists whether it's visible or not, so IN ADDITION TO the screen buffer, there is other memory needed for all the rest of the window data.

My only against Eug's points is that I'm not sure whether the windows' video data is all saved in video RAM when it's not visible. It's a detail of how the OS interacts with the video system that I'm not familiar enough with; it's possible that the non-visible data is shifted into active VRAM as needed-I'm looking forward to hearing which way it really goes.

[Switched2Mac]

Originally Posted by Eug Wanker

Incorrect. The memory usage for EVERY window on screen has be calculated separately, and added to the total.

For a single screen, 32 MB isn't great but OK for average usage. For dual screens, it's inadequate, since each screen gets only 16 MB.

IMO, all Macs from now on should have at least 64 MB GPU memory minimum.

No. Correct.

What you are referring to is the OS management of the individual windows. This happens in software at the OS-level. The memory that stores the data in your windows is managed by OS X and comes out of system RAM, not video RAM.

I was referring strictly to the firmware/hardware in the video chipset. The ATI Radeon 9550 doesn't know anything about the operating system "windows", and it doesn't need to.

The display that you see at any given second on your iBook is an actual "live" area in video memory. That "live" area is only 3 megs for the iBook G4 1024 x 768 LCD display. At any given instant, the total viewable pixels of all the OS's windows cannot exceed the total pixels physically available on the LCD display.

The video drivers handle any upper-level communication with the operating system.

Eug, why do you feel you need more? What is it that you cannot run?

Thanks to ghporter for the assist too.

[Eug Wanker]

Originally Posted by Switched2Mac

No. Correct.

What you are referring to is the OS management of the individual windows. This happens in software at the OS-level. The memory that stores the data in your windows is managed by OS X and comes out of system RAM, not video RAM.

Wrong again

Eug, why do you feel you need more? What is it that you cannot run?

Just try doing actual monitor spanning with a 64 MB GPU. With 32 MB per screen it's not that hard to get certain video actions to stutter significantly, especially if you have mid-sized screens. With 64 MB per screen it's a lot harder to get this happen.

Now, I mentioned 32 MB per screen. Try monitor spanning with a 16 MB per screen... Once you open several windows on each screen things like Exposé quickly will become stuttery, like if you were running a Rage Pro (which doesn't support Quartz Extreme) or something like that. That's what one gets with the iBook. It's no surprise that Apple recommends a minimum of 32 MB for just basic OS usage (for a single screen).

It's less of an issue on the iBook if you consider there is no official monitor spanning, and the screen is only 1024x768 anyway, so there's not much point in having a bazillion windows open. Thus, 32 MB becomes acceptable with the iBook for these reasons, but to say that only 10% of the iBook's video memory is used is simply wrong. And if you do want to do monitor spanning on an iBook, then watch out...

[Switched2Mac]

Originally Posted by Eug Wanker

Wrong again

Just try doing actual monitor spanning with a 64 MB GPU. With 32 MB per screen it's not that hard to get certain video actions to stutter significantly, especially if you have mid-sized screens. With 64 MB per screen it's a lot harder to get this happen.

Now, I mentioned 32 MB per screen. Try monitor spanning with a 16 MB per screen... Once you open several windows on each screen things like Exposé quickly will become stuttery, like if you were running a Rage Pro (which doesn't support Quartz Extreme) or something like that. That's what one gets with the iBook. It's no surprise that Apple recommends a minimum of 32 MB for just basic OS usage (for a single screen).

It's less of an issue on the iBook if you consider there is no official monitor spanning, and the screen is only 1024x768 anyway, so there's not much point in having a bazillion windows open. Thus, 32 MB becomes acceptable with the iBook for these reasons, but to say that only 10% of the iBook's video memory is used is simply wrong. And if you do want to do monitor spanning on an iBook, then watch out...

And that link shows the "Frame Buffer" to which I am referring. Again, the video card knows nothing of the OS windows. That is at the OS level.

You are correct, though, that more video RAM is a good thing. I totally agree.

However, the iBook is aimed at the low-end. What you envision is not inline with what Apple is currently marketing. Why does everyone insist on crying about the lack of features in the iBook?

When adding those features, you end up with a PowerBook in an iBook shell. Does anyone think that this makes marketing sense? And, of course, adding those things makes the price creep closer to that of the PowerBook.

"...oh, why doesn't the iBook have more memory, more video memory, SuperDrive, etc..."

I see this in the forums and hear it from friends. Again, the iBook is the low-end. And frankly, it is quite nice at that.

As far as stuttering goes, I run the built-in LCD (1024 x 768) and an external LCD at 1280 x 1024 at the same time. Expose never stutters for me.

And you remind me of another point, the iBook was not meant to use spanning. So really, in terms of the iBook, this discussion is pointless in Apple's marketing mind. They fully intended for the full 32 meg of VRAM for the built-in display. Nothing more.

[Eug Wanker]

Originally Posted by Switched2Mac

And that link shows the "Frame Buffer" to which I am referring. Again, the video card knows nothing of the OS windows. That is at the OS level.

Did you read the rest of that page?

The spanning issue is a separate issue I agree, but the bottom line is that your 3 MB number is just plain wrong, which is why I posted in the first place.

[Switched2Mac]

Originally Posted by Eug Wanker

Did you read the rest of that page?

The spanning issue is a separate issue I agree, but the bottom line is that your 3 MB number is just plain wrong, which is why I posted in the first place.

Why is the 3 MB number wrong?

This is all I said:

So it takes only 3 megs of your precious 32 megs to actually display the screen.

"... to actually display the screen."

I stated nothing more than what you see. I did not say that was all the video memory you need.

Do the math. Each image (in real-time) that you see on your display takes only 3 MB of memory. I did NOT say that is all it takes. Other buffering certainly takes place.

That number is not wrong, review the original post. If I made a mathematical error, by all means, post your own calculations to correct me.

I never claimed to be perfect...

[Eug Wanker]

Originally Posted by Switched2Mac

Other buffering certainly takes place.

Yes, in video RAM. Thus, the more windows are open, the more video RAM is used. You had claimed that only system RAM would be used for this:

Originally Posted by Switched2Mac

What you are referring to is the OS management of the individual windows. This happens in software at the OS-level. The memory that stores the data in your windows is managed by OS X and comes out of system RAM, not video RAM.

Your above statement is not correct. EVERY window open eats up more video RAM. ie. In 10.2 Jaguar 10.2 and beyond, the amount of GPU memory is very important.

32 MB on the iBook is acceptable, but is far from ideal. IMO, starting in 2006 even the low end consumer Macs (including both the iBook and the Mac mini) should have 64 MB of GPU memory, unless Apple is willing to continue to drop prices even further compared to the competition.