[Simon]

Although Apple says it's a HD 2600 PRO, it's actually not:



It appears that instead of using a HD 2600 PRO like Apple claims in their specs, they are actually using a Mobility HD 2600 XT that has been slightly underclocked on the new iMac.

The XT is actually better than the PRO, but OTOH the iMac's GPU is indeed the mobile verion. There is no Mobility HD 2600 PRO (the Mobility 2600 comes either as 2600 or 2600 XT) so Apple's original PRO moniker together with the missing 'Mobility' in their specs led many to believe the new iMac actually used the desktop version of the HD 2600. But now we can be certain this is not the case. On the bright side the Mobility HD 2600 series shares the same feature set support as the desktop counterpart, as well as the addition of the battery conserving PowerPlay 7.0.

Here are more details on the iMac's GPU:

Manufacturer : ATI Technologies Inc (Apple Computer Inc)
Model : ATI Technologies Inc
Bus Type : PCI-Express
Total Memory : 256 MB
Texture Memory : 500 MB
Processor : ATI Radeon Graphics Processor (0x9583)
Converter : Internal DAC(400MHz)
Refresh Rate (min/max) : 60/200 Hz

GPU Information :
Number of GPU : 1
Memory Type : SDRAM
GPU Frequency : SDRAM
Pixel Shader Version : 3.0

GPU Configuration :
Technology CrossFire : No

General Features :
Width : 432 mm
Height : 270 mm
Pixel per inch : 96x96 dpi
bits per pixel : 32
Colour Bits/Planes : 1
Brushes : 4294967295
Pens : 4294967295
Markers : 0
Device Fonts : 0
Device Colours : 4294967295
Clip Output to Rectangle : Yes
Hardware Acceleration : Yes

Blend and Shade Capabilities :
GradientFill Rectangle : No
GradientFill Traingle : No
Per Pixel AlphaBlend : Yes
Premultiplied Alpha : No

Raster Capabilities :
Banding : No
Transfer Bitmaps : Yes
Bitmap >64 KB : Yes
Fonts larger than 64 K : Yes
DIBs : Yes
DIBTODEV : Yes
Flood Fills : Yes
Scaling : No
StretchBlt : Yes
StretchDIB : Yes

Curves Capabilities :
Chord Arcs : Yes
Circles : Yes
Elipses : Yes
Interiors : Yes
Pie Wedges : Yes
Rounded Rectangles : Yes
Styled Borders : Yes
Wide Borders : Yes
Wide, Styled Borders : Yes

Lines Capabilities :
Interiors : Yes
Markers : Yes
Polylines : Yes
Polymarkers : Yes
Styled : Yes
Wide : Yes
Wide, Styled : Yes

Polygonal Capabilities :
Interiors : Yes
Alternate Fill Polygons : Yes
Winding Fill Polygons : Yes
Rectangles : Yes
Scan Lines : Yes
Styled Borders : Yes
Wide Borders : Yes
Wide, Styled Borders : Yes

Text Capabilities :
Stroke Precision : Yes
Stroke Clip Precision : Yes
90° Character Rotation : No
Any Angle Character Rotation : No
Independent X-Y Scaling : No
Double Weighted Characters : No
Italic : No
Underline : Yes
Strikeout : Yes
Raster Fonts : Yes
Vector Fonts : Yes

Color Management Capabilities :
CMYK : No
Gamma Ramp : Yes
ICM Device : No

[Simon]

More numbers:

The iMac's HD 2600 XT:
Core: 600 MHz
Memory: 1370 MHz (685 MHz x 2)

And here's ATI's usual clocking:
Desktop HD2600 Pro
Core: 550 MHz
Memory: 1400 MHz (700 MHz x 2)

Mobility HD2600 XT
Core: 700 MHz
Memory: 1500 MHz (750 MHz x 2)

So Apple downclocked the Mob 2600 XT to closer match the desktop-class 2600 PRO. The good news is they went for the 2600 XT hardware which means it is in theory capable of running ~30% faster than what you get out of the box. There's a fair chance the ATI tool can be used to get the card up to 'regular' XT speeds.

[Simon]

What I still don't understand is why Apple chose to call it a 2600 PRO when it's actually neither a desktop 2600 nor a PRO. People will be glad it's a 2600 XT, so why hide the fact? They've underclocked before and not changed the GPU name either, so why now?

[P]

When they underclock, they don't mention the moniker (Pro or XT or GT or Ultra or whatever) at all. I guess this time they wanted to indicate the approximate performance with a moniker and picked the closest analog.

BTW, how does Windows determine what GPU it is? My guess: ATi has defined all their boards, and the software picked the closest one. Do not assume that the video memory included can support the higher clockspeed. The GPU core probably will, but that's only part of the story.

[Simon]

Originally Posted by P 

BTW, how does Windows determine what GPU it is?

It queries the ATi chip ID. Turns out that's 0x9583 (it's in the data I posted above).

That's the unique ID of the Mobility HD 2600 XT.

[kenna]

hmmm interesting, but why would Apple make their graphics card LESS powerful???

Sorry if this is a stupid question im a noob

[MacosNerd]

Its not a stupid question and its been the bane of many mac users.

For laptops it was an easy answer, heat battery life etc. For a desktop who knows?

[Grrr]

Well, for an underclocked card, it sure does trip over itself a lot! But I hope and expect Apple will soon have that fixed in a software update.

Interesting news none the less though, thanks for sharing

Oh, and one more thing.....
Am I right in thinking these latest iMacs have a GPU on an mxm type socket? I ask because after seeing a new imac taken apart on this site, it appears to show a square card on an mxm type socket? Disassembled iMac (2007 Mid) by KODAWARISAN_Page2
Look at the 4th pict down the page, the square'ish looking card with the red & white sticker on it near the top.
If thats not the GPU, then what is it? And if it is the GPU, then upgrades are possible?

[Simon]

Originally Posted by MacosNerd 

For laptops it was an easy answer, heat battery life etc. For a desktop who knows?

The iMac is a desktop computer, but it has notebook components and it can't be cooled like a desktop either. In many things the iMac is more like a notebook than a desktop. Heat is a serious issue for the iMac - especially on the new iMac.

[seanc]

Originally Posted by Grrr 

Well, for an underclocked card, it sure does trip over itself a lot! But I hope and expect Apple will soon have that fixed in a software update.

Interesting news none the less though, thanks for sharing

Oh, and one more thing.....
Am I right in thinking these latest iMacs have a GPU on an mxm type socket? I ask because after seeing a new imac taken apart on this site, it appears to show a square card on an mxm type socket? Disassembled iMac (2007 Mid) by KODAWARISAN_Page2
Look at the 4th pict down the page, the square'ish looking card with the red & white sticker on it near the top.
If thats not the GPU, then what is it? And if it is the GPU, then upgrades are possible?

Looks like a solid part of the logic board to me and not detachable.
I think they were only MXM in the last gen 24" iMacs to make CTOs easier so that they could just transfer the card rather than the logic board.

[P]

The new iMacs do indeed have the GPU on MXM. Seanc: Look at the last picture, upper left corner, under the heatpipe. Now look down a little bit and you'll see the connection.

[seanc]

Originally Posted by P 

The new iMacs do indeed have the GPU on MXM. Seanc: Look at the last picture, upper left corner, under the heatpipe. Now look down a little bit and you'll see the connection.

Ah yes, you're correct. I didn't follow the card past the heatpipe and so didn't notice the connector.

Thanks for the correction.

[mduell]

Originally Posted by P 

The new iMacs do indeed have the GPU on MXM. Seanc: Look at the last picture, upper left corner, under the heatpipe. Now look down a little bit and you'll see the connection.

Can you swap the 7600GT MXM from the old iMac into the slot on the new iMac?

And are you sure the new slot is actually MXM? IIRC MXM is an nVidia-only thing; AMD has something similar, but not compatible.

[P]

I don't know if you can swap it - as far as I know, noone tried. MXM is something introduced by nVidia, but it is really just a subset PCIe with a different connector and was intended to be non-proprietary. This site has lots of examples of ATi GPUs on MXM, and a few of switching between nVidia and AMD/ATi.

[Simon]

Originally Posted by mduell 

And are you sure the new slot is actually MXM? IIRC MXM is an nVidia-only thing; AMD has something similar, but not compatible.

Good point. MXM is indeed an nVidia-only thing.

This slot is something else. Any chance it's actually just an Apple daughterboard (of course using the physical MXM connection) to make (future) BTO options easier and less expensive to implement?

[Grrr]

A quick Google shows that it has been open standard for a good couple of years?

InformIT: MXM: Finally, an open standard for laptop graphics > MXM: Finally, an open standard for laptop graphics

[mduell]

Originally Posted by Simon 

This slot is something else. Any chance it's actually just an Apple daughterboard (of course using the physical MXM connection) to make (future) BTO options easier and less expensive to implement?

Wouldn't surprise me, since Apple uses Quanta as an ODM, and Quanta has their own physically-MXM/logically-something-else connector/cards used in some of the laptops they produce.

[Simon]

So if that's actually the case all we then need is a mobility version of the HD 2900 XT and Apple to offer it as a BTO option.

[Pierre B.]

Originally Posted by Simon 

The iMac is a desktop computer, but it has notebook components and it can't be cooled like a desktop either. In many things the iMac is more like a notebook than a desktop. Heat is a serious issue for the iMac - especially on the new iMac.

Right, but if I am not mistaken, Apple has previously underclocked graphics cards even for the Power Mac/Mac Pro. This is a mystery to me.

[mduell]

HD2900XT is just another disappointment... go for 8700M GT.

Originally Posted by Pierre B. 

Right, but if I am not mistaken, Apple has previously underclocked graphics cards even for the Power Mac/Mac Pro. This is a mystery to me.

Most video cards from Apple are underclocked. I think they may be doing it just so they can buy cheaper chips (the ones that don't test at the nominal clockrates). Heat really isn't an issue in a full size workstation case.

[P]

Has Apple really underclocked Powermac/Mac Pro graphics? I wasn't aware. Cite an example, please. Even the Cube - which could have used it - used a fullspeed model. It was a pathetic little Rage 128 derivative, but wasn't underclocked.

The rumored RV670 is probably our best hope for a better future GPU. ATi has a good trackrecord for making good facelift parts, however, so it may not be all bad.

[cherry su]

Apparently (thru a quick Wiki), the 24" iMac uses a card based on the MXM form factor but offers no compatibility.

[Simon]

Just what I expected. They may be using an MXM connector, but that doesn't mean the card is actually MXM compliant and hence exchangeable.

[P]

The cards sent don't boot because of a firmware incompatibility - probably related to Apple using EFI. Afterall, you can't install any PC card in a Mac Pro either. We don't know whether the card is electrically compatible with MXM - wouldn't surprise me if it isn't, but innocent until proven guilty and all that.

[Simon]

But that's really not all that relevant either. For all practical purposes it's not an exchangeable card. Be that due to missing drivers, different firmware, or due to the actual wiring. iMac users aren't able to take any other existing MXM card and insert it in place of the stock card.

[P]

It only matters if you're a GPU manufacturer wanting to give it a shot...

No, not likely - too hard to get to inside the iMac, even if you did manage to get it to work, to be worth the upgrade for most people. The only upside is that this motherboard design makes it easier to allow BTO upgrades as well as quicker upgrades as better GPUs become available.

[mduell]

Originally Posted by P 

Has Apple really underclocked Powermac/Mac Pro graphics? I wasn't aware. Cite an example, please. Even the Cube - which could have used it - used a fullspeed model. It was a pathetic little Rage 128 derivative, but wasn't underclocked.

A few come to mind, but IIRC most have been slightly underclocked.

The X1900XT in the Mac Pro runs at 600Mhz core/650Mhz VRAM instead of 625/725.
The X800 in the PowerMac was underclocked from 500/1000 to 475/1000.
You can find a lot more examples on Google.

The mobile cards in the MacBook Pro/PowerBook typically had more substantial underclocks, up to 30% with the X1600.

[Judge_Fire]

Originally Posted by P 

Even the Cube - which could have used it - used a fullspeed model. It was a pathetic little Rage 128 derivative, but wasn't underclocked.

The ATI card in the Cube was (marketed as) a first gen Radeon. I got one of the early ones, without a fan. Quiet indeed, but ended up melting itself when playing Wolfenstein. Repairs put in the same chip with a noisy fan on top.

[P]

According to this, the Radeon was a BTO option. I think the Cube was one of the Macs affected by ATi upstaging Jobs.

[goMac]

The first Cubes had a Rage 128 as standard with a Radeon upgrade option. The second version ones moved entirely to NVidia. (GeForce 2) I'm not sure the GeForce 3 was offered as an option, but people have definitely put them in Cubes.

[Pierre B.]

Alright, new drivers for the aluminum iMac in the horizon. Where are the adventurous ones?

[Simon]

New GPU drivers:

lsbom /Library/Receipts/iMacSoftwareUpdate1.1.pkg/Contents/Archive.bom
. 41775 0/80
./System 40755 0/0
./System/Library 40755 0/0
./System/Library/Displays 40755 0/0
./System/Library/Displays/Overrides 40755 0/0
./System/Library/Displays/Overrides/DisplayVendorID-610 40755 0/0
./System/Library/Displays/Overrides/DisplayVendorID-610/DisplayProductID-9c6a 100644 0/0 4127 2078667664
./System/Library/Extensions 40755 0/0
./System/Library/Extensions/ATINDRV.kext 40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents 40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns 40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Hypoprion.kext 40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Hypoprion.kext/Contents 40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Hypoprion.kext/Contents/Info.plist 100644 0/0 2297 1650846376
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Hypoprion.kext/Contents/MacOS 40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Hypoprion.kext/Contents/MacOS/ATY_Hypoprion 100755 0/0 679460 2902294699
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Hypoprion.kext/Contents/PkgInfo 100644 0/0 9 2853408188
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Hypoprion.kext/Contents/version.plist 100644 0/0 465 2135851948
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Iago.kext 40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Iago.kext/Contents40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Iago.kext/Contents/Info.plist 100644 0/0 2262 2893439862
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Iago.kext/Contents/MacOS 40755 0/0
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Iago.kext/Contents/MacOS/ATY_Iago 100755 0/0 679376 572194728
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Iago.kext/Contents/PkgInfo 100644 0/0 9 2853408188
./System/Library/Extensions/ATINDRV.kext/Contents/PlugIns/ATY_Iago.kext/Contents/version.plist 100644 0/0 465 2135851948
./System/Library/Extensions/ATIRadeonX2000.kext 40755 0/0
./System/Library/Extensions/ATIRadeonX2000.kext/Contents 40755 0/0
./System/Library/Extensions/ATIRadeonX2000.kext/Contents/Info.plist 100644 0/0 3048 2430932426
./System/Library/Extensions/ATIRadeonX2000.kext/Contents/MacOS 40755 0/0
./System/Library/Extensions/ATIRadeonX2000.kext/Contents/MacOS/ATIRadeonX2000 100644 0/0 857084 2526009243
./System/Library/Extensions/ATIRadeonX2000.kext/Contents/PkgInfo 100644 0/0 9 2853408188
./System/Library/Extensions/ATIRadeonX2000.kext/Contents/PlugIns 40755 0/0
./System/Library/Extensions/ATIRadeonX2000.kext/Contents/version.plist 100644 0/0 465 2135851948
./System/Library/Extensions/ATIRadeonX2000GA.plugin 40755 0/0
./System/Library/Extensions/ATIRadeonX2000GA.plugin/Contents 40755 0/0
./System/Library/Extensions/ATIRadeonX2000GA.plugin/Contents/Info.plist 100644 0/0 1216 3495896374
./System/Library/Extensions/ATIRadeonX2000GA.plugin/Contents/MacOS 40755 0/0
./System/Library/Extensions/ATIRadeonX2000GA.plugin/Contents/MacOS/ATIRadeonX2000GA 100755 0/0 52044 3429959767
./System/Library/Extensions/ATIRadeonX2000GA.plugin/Contents/PkgInfo 100644 0/0 9 668541015
./System/Library/Extensions/ATIRadeonX2000GA.plugin/Contents/version.plist 100644 0/0 465 2135851948
./System/Library/Extensions/ATIRadeonX2000GLDriver.bundle 40755 0/0
./System/Library/Extensions/ATIRadeonX2000GLDriver.bundle/Contents 40755 0/0
./System/Library/Extensions/ATIRadeonX2000GLDriver.bundle/Contents/Info.plist 100644 0/0 865 760727836
./System/Library/Extensions/ATIRadeonX2000GLDriver.bundle/Contents/MacOS 40755 0/0
./System/Library/Extensions/ATIRadeonX2000GLDriver.bundle/Contents/MacOS/ATIRadeonX2000GLDriver 100755 0/0 2555664 2670489101
./System/Library/Extensions/ATIRadeonX2000GLDriver.bundle/Contents/PkgInfo 100644 0/0 9 668541015
./System/Library/Extensions/ATIRadeonX2000GLDriver.bundle/Contents/version.plist100644 0/0 465 2135851948
./System/Library/Extensions/ATIRadeonX2000VADriver.bundle 40755 0/0
./System/Library/Extensions/ATIRadeonX2000VADriver.bundle/Contents 40755 0/0
./System/Library/Extensions/ATIRadeonX2000VADriver.bundle/Contents/Info.plist 100644 0/0 861 2764508562
./System/Library/Extensions/ATIRadeonX2000VADriver.bundle/Contents/MacOS 40755 0/0
./System/Library/Extensions/ATIRadeonX2000VADriver.bundle/Contents/MacOS/ATIRadeonX2000VADriver 100755 0/0 113040 2537283261
./System/Library/Extensions/ATIRadeonX2000VADriver.bundle/Contents/PkgInfo 100644 0/0 9 668541015
./System/Library/Extensions/ATIRadeonX2000VADriver.bundle/Contents/version.plist100644 0/0 465 2135851948
./usr 40755 0/0
./usr/libexec 40755 0/0
./usr/libexec/oah 40755 0/0
./usr/libexec/oah/Shims 40755 0/0
./usr/libexec/oah/Shims/GLEngine.bundle 40755 0/0
./usr/libexec/oah/Shims/GLEngine.bundle/GLEngine 100755 0/0 509452 366441641
./usr/libexec/oah/translate 100755 0/0 3210060 3888826477

[ghporter]

Originally Posted by Simon 

New GPU drivers...

Thanks for the nudge-I hadn't installed that update yet (hadn't seen it). About to restart after installing...

[Grrr]

A couple of posts from users over on Macrumors report quite substantial performance increases with this update. I was more concerned about stability than the speed boost.
I've not been able to test much (Only 30 mins or so) but it hasnt frozen at all yet. So, so far so good.

[ghporter]

Originally Posted by Grrr 

I've not been able to test much (Only 30 mins or so) but it hasnt frozen at all yet. So, so far so good.

Your iMac was freezing?

[Grrr]

Originally Posted by ghporter 

Your iMac was freezing?

Yes.. UT2004 was the main culprit. It would always freeze within 20 mins or so. But it seems ok now.
There was a few other things which could trip the iMac into locking up too (Including some of Apples own software). And all the lock ups were graphics drivers related.
Its a little early to be certain, but currently it looks like the update has cured these highly annoying gremlins.

Better late than never.

[funkboy]

Originally Posted by Grrr 

Better late than never.

So... benchmarks?

Patiently awaiting a matte screen option from Apple... and a post from Fat Barry in the Lounge... both of which seem like they'll never happen...

[Grrr]

Originally Posted by funkboy 

So... benchmarks?

I've only run X-bench to test.
All the scores for each test were near enough identical, bar one..
The user interface test. On my imac at least, went from a score of 298 to 427. But as I say, the other tests gave much the same results as before. Which doesnt entirely tie in with what I read on macrumors, but no matter.

I need to give it more time to check the stability, which to me was far more important than any performance boost. But so far, its all good.

[PaperNotes]

BareFeats says slower.

[Grrr]

Originally Posted by PaperNotes 

BareFeats says slower.

Barefeats tests were so cr@p, they didn't even notice the rather significant issue of the Macs locking up on an alarmingly frequent basis. Throwing their credibility clean out the window, in my opinion.

My own test showed perhaps a marginal drop in a couple of graphics tests, but a large increase in 1 or 2 others, notably the user interface test. Overall performance however, is nigh on identical.

The stability is the real gain here, making the update very much worthwhile.

[PaperNotes]

I note that BareFeats said that the new drivers aren't optimised by AMD. BF should know that AMD/ATI leave optimization of mobility series GPUs up to computer manufacturers. Apple has chosen to base all their current OS X and Boot Camp drivers on Catalyst 7.7 which are old now (May 2007). The latest Catalyst is 7.9