Reason for different die sizes on 384sp GCN 1.0 desktop and mobile GPUs?

[cbn]

I noticed the Oland and Litho/Mars 384sp GCN 1.0 GPUs are listed with different die sizes (90mm2 vs 77mm2). This even though the listed specs (Shading Units, TMUs, ROPs, PCIe bus, memory bus) are the same.



Oland (used on the desktop) is 90mm2 on 28nm.

Example:

(R7 250) https://www.techpowerup.com/gpudb/2459/radeon-r7-250



Litho and Mars (used on mobile) are 77mm2 on 28nm.

Examples:

(R7 M370) https://www.techpowerup.com/gpudb/2695/radeon-r7-m370

(HD 8750M) https://www.techpowerup.com/gpudb/1968/radeon-hd-8750m



Does anyone know why this is this?

Is one fabbed at Global Foundries while the other set is fabbed at TSMC (or vice versa)? Or is there a different reason for the die size difference?

 

[therealnickdanger]

My first guess would be that it's a typo or that they are referring to package size. My second guess would be that a change in power delivery or something removed for the mobile environment.

 

[cbn]

My first guess would be that it's a typo or that they are referring to package size.

Oland is listed as 90mm2 in these links as well:

http://pc.watch.impress.co.jp/video/pcw/docs/751/980/p06.pdf (You need to Zoom in to read it)

https://en.wikipedia.org/wiki/AMD_Radeon_Rx_200_series#Radeon_R7_250

And this link lists Mars as 76.5 mm2:

http://www.expreview.com/22931.html

Although with that noted, Wikipedia is listing Mars as 85mm2:

https://en.wikipedia.org/wiki/Radeon_HD_8000_series#Solar_System_.28HD_8xxxM.29_series

 

[laamanaator]

If i remember correctly, oland has two memory controllers. One for DDR3 and one for GDDR5. Although I'm not sure about it. That'd explain the difference in die sizes

 

[cbn]

If i remember correctly, oland has two memory controllers. One for DDR3 and one for GDDR5. Although I'm not sure about it. That'd explain the difference in die sizes

Mars also has a DDR3 controller (Example below):

https://www.techpowerup.com/gpudb/1967/radeon-hd-8730m