Többmagos/sokmagos processzorok-2

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1 Többmagos/sokmagos processzorok-2
Sima Dezső 2014 Október Version 1.4

2 Áttekintés 1. Többmagos processzorok megjelenésének szükségszerűsége
2. Homogén többmagos processzorok 2.1 Hagyományos többmagos processzorok 2.2 Sokmagos processzorok 3. Heterogén többmagos processzorok 3.1 Mester/szolga elvű többmagos processzorok 3.2 Csatolt többmagos processzorok 4. Kitekintés

3 3. Heterogén többmagos processzorok

4 3. Heterogén többmagos processzorok (1)
Multicore processors Homogenous multicores Heterogenous multicores Conventional MC processors Manycore processors Master/slave architectures Add-on architectures 2 ≤ n ≤ 8 cores with >8 cores Desktops Servers MPC CPU GPU General purpose computing Experimental systems, prototypes/in production MM/3D/HPC production stage HPC, mobiles production stage 3.1 ábra Többmagos processzorok főbb osztályai

5 3.1 Heterogén többmagos mester/szolga elvű TP-ok
A Cell processzor

6 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (1)
Cell BE Sony, IBM és Toshiba közös terméke Cél: Játékok/multimédia, HPC alkalmazások Playstation 3 (PS3) QS2x Blade Szerver család (2 Cell BE/blade) Előzmények: 2000 nyara: Az architektúra alapjainak meghatározása 02/2006: Cell Blade QS20 08/ Cell Blade QS21 05/ Cell Blade QS22

7 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (2)
SPE: Synergistic Procesing Element SPU: Synergistic Processor Unit SXU: Synergistic Execution Unit LS: Local Store of 256 KB SMF: Synergistic Mem. Flow Unit EIB: Element Interface Bus PPE: Power Processing Element PPU: Power Processing Unit PXU: POWER Execution Unit MIC: Memory Interface Contr. BIC: Bus Interface Contr. XDR: Rambus DRAM 3.1.1 ábra: A Cell BE blokk diagramja [1]

8 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (3)
3.1.2 ábra: A Cell BE lapka (221mm2, 234 mtrs) [1]

9 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (4)
3.1.3 ábra: A Cell BE lapka – EIB [1]

10 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (5)
3.1.4 ábra: Az EIB működési elve [1]

11 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (6)
3.1.5 ábra: Konkurens átvitelek az EIB-en [1]

12 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (7)
Példa egy komplex alkalmazás futtatása (digitális TV dekódolása) a Cell processzoron [2]

13 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (8)
A Cell teljesítménye és a NIK részvétele a Cell teljesítmény-vizsgálataiban 3.2 GHz: QS21 Csúcs SP FP: 409,6 GFlops (3.2 GHz x 2x8 SPE x 2x4 SP FP/cycle) Cell BE - NIK 2007: Faculty Award (Cell 3Đ app./Teaching) 2008: IBM – NIK Kutatási Együttműködési Szerződés: Teljesítményvizsgálatok IBM Böblingen Lab IBM Austin Lab

14 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (9)
The Roadrunner 6/2008 : International Supercomputing Conference, Dresden A világ 500 leggyorsabb számítógépe listáján (Top500): 1. Roadrunner 1 Petaflops (1015) fenntartott teljesítmény (Linpack)

15 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (10)
3.1.6 ábra:A világ leggyorsabb számítógépe: IBM Roadrunner (Los Alamos 2008) [3]

16 3.1 Heterogén mester/szolga elvű TP-ok - A Cell (11)
3.1.7 ábra: A Roadrunner főbb jellemzői [1]

17 3.2 Heterogén csatolt többmagos processzorok

18 3.2 Heterogén csatolt többmagos processzorok (1)
Multicore processors Homogenous multicores Heterogenous multicores Conventional MC processors Manycore processors Master/slave architectures Add-on architectures 2 ≤ n ≤ 8 cores with >8 cores Desktops Servers MPC CPU GPU General purpose computing Experimental systems, prototypes/in production MM/3D/HPC production stage HPC, mpbiles production stage 3.2.1 ábra: Többmagos processzorok főbb jellemzői

19 3.2 Heterogén csatolt többmagos processzorok (2)
Csatolt elvű végrehajtás elve GPGPU-k esetén (a legegyszerűbb (kötegelt) szervezést feltételezve) [4] Host Device kernel0<<<>>>() (Adatpárh. progr.) kernel1<<<>>>()

20 3.2 Heterogén csatolt többmagos processzorok (3)
Megjegyzés a működési elvhez Heterogén csatolt többmagos processzorok: feldolgozás gyorsítók (accelerators) A működési elv szempontjából előzmény: heterogén csatolt társprocesszoros rendszerek Példák: korai személyi számítógépek lebegőpontos társprocesszorokkal Intel Az Intel 486-nak már volt saját “on-chip” lebegőpontos egysége (FPU) (az SX és SL modelek kivételével)

21 Heterogén csatolt többmagos processzorok Okostelefonok/táblagépek
Heterogén csatolt többmagos processzorok legfontosabb implementációi Heterogén csatolt többmagos processzorok Integrált grafika Okostelefonok/táblagépek

22 3.2.1 Az Integrált grafika megjelenése

23 3.2.1 Az Integrált grafika megjelenése (1)
Áttérés angol nyelvű slide-ok használatára

24 3.2.1 Az Integrált grafika megjelenése (2)
Implementation of integrated graphics Implementation of integrated graphics In the north bridge In a multi-chip processor package on a separate die On the processor die Both the CPU and the GPU are on separate dies and are mounted into a single package P South Bridge Mem. NB IG South Bridge Mem. NB P GPU CPU Periph. Contr. Mem. CPU GPU P Implementations about Intel’s Havendale (DT) and Auburndale (M) (scheduled for 1H/2009 but cancelled) Arrandale (DT, 1/2010) and Clarkdale (M, 1/2010) Intel’s Sandy Bridge (1/2011) and Ivy Bridge (4/2012) etc. AMD’s Swift (scheduled for 2009 but canceled) AMD’s Bobcat-based APUs (M, 1/2011) Llano APUs (DT, 6/2011) Trinity APUs (DT, Q4/2012) etc.

25 3.2.1 Az Integrált grafika megjelenése (3)
Implementation of integrated graphics Implementation of integrated graphics In the north bridge In a multi-chip processor package on a separate die On the processor die Both the CPU and the GPU are on separate dies and are mounted into a single package P South Bridge Mem. NB IG South Bridge Mem. NB P GPU CPU Periph. Contr. Mem. CPU GPU P Implementations about Intel’s 2. gen. Nehalem based Havendale (DT) and Auburndale (M) (scheduled for 1H/2009 but cancelled) Westmere based Arrandale (DT, 1/2010) and Clarkdale (M, 1/2010) Intel’s Sandy Bridge (1/2011), Ivy Bridge (4/2012) etc. AMD’s Swift (scheduled for 2009 but canceled) AMD’s Bobcat-based APUs (M, 1/2011) Llano APUs (DT, 6/2011) Trinity APUs (DT, Q4/2012) etc.

26 3.2.1 Az Integrált grafika megjelenése (4)
Example 1: Intel’s Havendale (DT) and Auburndale (M) multi-chip CPU/GPU processor plans [5] Revealed in 9/2007. Scheduled for 1H/2009 but cancelled about 1/2009. Both parts were based on the 2. gen. Nehalem (Lynnfield) architecture (45 nm), as shown below. DMI DDR3 Graphics DDR3 IMC PCI-E Power Thread 8M Core Ibexpeak PCH PCIe, SATA, NVRAM, etc. Display Analog Digital I/O Control Processors I/O functions Lynnfield processor (Monolithic die) Display Link DMI (Direct Media Interface) 4 PCIe lanes) DDR3 Graphics MCP Processor Power 4M PCI-E DDR3 IMC GPU Thread Core SDVO, HDMI Display Port, DVI Ibexpeak PCH VGA PCIe, SATA, NVRAM, etc. Analog Digital I/O Control Processors I/O functions No integrated graphics Havendale processor (Multi-chip package – MCP) Same LGA 1160 platform Schedule: 2H ’08 First Samples 1H ’09 Production TDP < 95 W

27 3.2.1 Az Integrált grafika megjelenése (5)
Example 2: Intel’s Westmere-EP based multi-chip CPU/GPU processors (2010)-1 [6] Clarkdale (desktop) Arrandale (mobile) The CPU and the GMA chips are connected by the QPI bus.

28 3.2.1 Az Integrált grafika megjelenése (6)
Positioning of Clarkdale (DT) and Arrandale (M) in Intel’s roadmap [7]

29 3.2.1 Az Integrált grafika megjelenése (7)
Single chip “chipset”, called PCH for Intel’s Westmere-EP based multi-chip CPU/GPU processors (2010) [7] PCH (Peripheral Control Hub)

30 3.2.1 Az Integrált grafika megjelenése (8a)
(Dedicated graphics via graphics card) Removing the memory controller (MC) from the north bridge to the processor (IMC) [7] (Dedicated graphics via graphics card)

31 3.2.1 Az Integrált grafika megjelenése (8)
(Dedicated graphics via graphics card) Removing integrated graphics (IGFX) from the north bridge to the processor [7] (Dedicated graphics via graphics card) On extra die

32 3.2.1 Az Integrált grafika megjelenése (8b)
(Dedicated graphics via graphics card) Connecting discrete graphics immediately to the processor instead the north bridge [7] (Dedicated graphics via graphics card) PCIe 2.0

33 3.2.1 Az Integrált grafika megjelenése (9)
Implementation of commercial graphics on the processor die Implementation of integrated graphics In the north bridge In a multi-chip processor package on a separate die On the processor die Both the CPU and the GPU are on separate dies and are mounted into a single package P South Bridge Mem. NB IG South Bridge Mem. NB P GPU CPU Periph. Contr. Mem. CPU GPU P Implementations around Intel’s Havendale (DT) and Auburndale (M) (scheduled for 1H/2009 but cancelled) Arrandale (DT, 1/2010) and Clarkdale (M, 1/2010) Intel’s Sandy Bridge (1/2011) and Ivy Bridge (4/2012) etc. AMD’s Swift (scheduled for 2009) AMD’s Bobcat-based APUs (M, 1/2011) and Llano APUs (DT, 6/2011) Trinity APUs (DT, Q4/2012) etc.

34 3.2.2 Intel’s Sandy Bridge

35 3.2.2 Intel’s Sandy Bridge (1)
Key microarchitecture features of the Sandy Bridge vs the Nehalem

36 256 b/cycle Ring Architecture
3.2.2 Intel’s Sandy Bridge (2) Die plot of the 4C Sandy Bridge processor [9] 32K L1D (3 clk) AVX 256 bit 4 Operands 256 KB L2 (9 clk) Hyperthreading AES Instr. VMX Unrestrict. 20 nm2 / Core PCIe 2.0 @ GHz (to L3 connected) 256 b/cycle Ring Architecture (25 clk) DDR3-1600 Sandy Bridge 4C 32 nm 995 mtrs/216 mm2 ¼ MB L2/C 8 MB L3

37 3.2.2 Intel’s Sandy Bridge (3)
Block diagram of Intel’s Sandy Bridge with 6 Series PCH [10] Core i3-21xx, 2C, 2/2011 Core i5-23xx/24xx/25xx, 4C, 1/2011 Core i7-26xx, 4C, 1/2011 1 Intel 6 series PCH1 1Except P67 that does not provide a display controller in the PCH

38 3.2.2 Intel’s Sandy Bridge (4)
Graphics performance increase of subsequent Core generations [33] Haswell Sandy Bridge Ivy Bridge

39 3.2.3 AMD’s Swift Fusion APU plan

40 3.2.3 AMD’s Swift Fusion APU plan (1)
Preliminaries In 10/2006 AMD acquired the graphics firm ATI and at the same day they announced that “AMD plans to create a new class of x86 processors that integrate the central processing unit (CPU) and graphics processing unit (GPU) at the silicon level, codenamed “Fusion [13].” Remark Although in the above statement AMD designated the silicon level integration of the CPU and GPU as the Fusion initiative, in some other publications they call both the package level and the silicon level integration of the CPU and GPU as the Fusion technology, as shown in the next figure [14]

41 3.2.3 AMD’s Swift Fusion APU plan (2)
Extended interpretation of the term Fusion technology in some AMD publications [14] Despite this disambiguation, subsequently AMD understood the term Fusion usually as the silicon level integration of the CPU and the GPU.

42 3.2.3 AMD’s Swift Fusion APU plan (3)
In 12/2007 at their Financial Analyst Day AMD gave birth to a new term by designating their processors implementing the Fusion concept as APUs (Accelerated Processing Units). At the same time AMD announced their first APU family called the Swift family [15] as well.

43 3.2.3 AMD’s Swift Fusion APU plan (4)
In 11/2008 again at their Financial Analyst Day AMD postponed the introduction of Fusion-based APU processors until the company transitions to the 32 nm technology [16] [17]. No Swift APU!

44 3.2.3 AMD’s Swift Fusion APU plan (5)
Remark This is a similar move as done by Intel with their 45 nm Havendale (DT) and Auburndale (M) in-package integrated multi-chip CPU+GPU projects. As leaked from industry sources in 1/2009 Intel canceled their 45 nm multi-chip processor plans in favor of 32-nm multi-chip processors to be introduced in Q1/2010 [18].

45 3.2.4 AMD’s K12 (Llano)-based APU lines

46 3.2.4 AMD’s K12 (Llano)-based APU lines-1
3.2.4 Overview of AMD’s desktop and mobile APU lines-1 (based on [37]) Fam. 15h Mod. 00h-0Fh Fam. 15h Mod. 10h-1Fh K10 Steamroller Fam. 15h Mod. 30h-3Fh GPU-less Family 15h lines 28 nm K / K / F a m i l y 11h l i n e s Fam. 12h Hound (K10.5/Stars) Bobcat Fam. 14h Brazos DX11 GPU Core 1-2 Cores 1MB (Zacate) DDR3 Jaguar Fam. 16h Family 12h – 16h APU (Fusion) lines Hound (K10.5/Stars) Family 11h Jaguar Fam. 16h Fam. 14h Brazos 2 Cores 1MB (Desna) DX11 GPU Core DDR3 Tablet

47 3.2.4 AMD’s K12 (Llano)-based APU lines-2
3.2.4 Overview of AMD’s notebook and tablet APU lines-2 PWc Basically PWc tuned by Tdie m Tdie c Basically Tdie c tuned by Tdie m PWc ≤ TDP: Turbo mode PWc < TDP: Decrease fc PWc ≤ TDP: Turbo mode PWc ≥ TDP: Decrease fc Tdie c ≤ Tdie c max: Turbo mode Tdie c > Tdie c max: Decrease fc Tdie c ≤ Tdie c max: Turbo mode Tdie c > Tdie c max: Decrease fc If Tdie m < Tdie m max increase fc additionally up to fc max ,as long as Tdie m ≤ Tdie m max If Tdie m < Tdie m max increase fc additionally up to fc max ,as long as Tdie m < Tdie m max Intel’s Turbo Boost in Nehalem (2008) Intel’s Turbo Boost 2.0 in Sandy Bridge (2011) Ivy Bridge (2012) Haswell (2013) Westmere based Arrandale M (2010) AMD’s Turbo Core 2.0 in K12 Llano APU (2011) K16 Jaguar based Kabini/Temash (2013) AMD’s Turbo Core 3.0 in K15 Piledriver based Trinity (2012) AMD’s Hybrid Boost in K15 Piledriver based Richland (2013) PWc: Calculated power consumption PWm: Measured power consumption Tdie c: Calculated die temperature Tdie m: Measured die temperature

48 3.2.5 AMD’s K12 (Llano)-based APU lines (3)
3.2.4 AMD’s Llano-based APU lines [19] Introduced: 6/2011. The Llano line belongs to the Fusion APU (Accelerated Processing Unit) series as it includes beyond a number of CPUs also a GPU to accelerate vision computing (graphics and media). Processors of the Llano lines have up to 4 CPU cores and a GPU. Nevertheless, AMD sells Llano based desktop lines as well with disabled GPUs. These lines are branded as Athlon II X4/X2 or Sempron lines. 32 nm technology, 228 mm2, 1450 mtrs.

49 3.2.5 AMD’s K12 (Llano)-based APU lines (4)
Die plot of the Llano processor [20]

50 3.2.5 AMD’s K12 (Llano)-based APU lines (5)
Example: AMD’s Llano-based A-series mobile lines [21]

51 3.2.5 AMD’s K12 (Llano)-based APU lines (6)
Conceptual difference between AMD’s Fusion APU’s and Intel’s Sandy Bridge CPUs [22]

52 3.2.5 AMD’s K12 (Llano)-based APU lines (7)
AMD’s Llano APU processor with the A75 FCH [23] Lynx platform FCH: Fusion Control Hub

53 3.2.5 AMD’s K12 (Llano)-based APU lines (8)
Internal buses introduced in Llano’s Integrated Northbridge-1 [20]

54 3.2.5 AMD’s K12 (Llano)-based APU lines (9)
Internal buses introduced in Llano’s Integrated Northbridge-2 [20]

55 3.2.5 Okostelefonok, táblagépek

56 3.2.5 Okostelefonok, táblagépek-1
Ld. később külön fejezetként.

57 3.2.5 Okostelefonok, táblagépek-2
Példa 1: Texas OMAP 4 (OMAP 4460) Source: TI’s OMAP4460 in Samsung GALAXY Nexus with Android 4.0 October 21, 2011

58 3.2.5 Okostelefonok, táblagépek-3
Példa 2: Texas OMAP 5 (OMAP 5430) A15 MPCore: Up to 4 cores, in Texas’s implementation: 2 cores

59 3.3.2 Okostelefonok/táblagépek (4)

60 3.3.2 Okostelefonok/táblagépek (5)
Megjegyzés 9/2012 Texas bejelentés: az OMAP család fejlesztésének leállítása, fókuszálás autóipari elektrónika További gyártók: Qualcomm, Samsung, NVIDIA, Intel

61 4. Kitekintés

62 Heterogenous multicores
4. Kitekintés (1) Kitekintés Heterogenous multicores Master/slave architectures Add-on architectures Több CPU Több gyorsító 4.1 ábra: Hetererogén többmagos processzorok várható fejlődése

63 Referenciák

64 References (1) [1]: Wright C., Henning P., Bergen B., Roadrunner Tutorial, An Introduction to Roadrunner, and the Cell Processor, Febr , [2]: Blachford N., Cell Architecture Explained, v.02, 2005, [3]: Ricker T., World's fastest: IBM's Roadrunner supercomputer breaks petaflop barrier using Cell and Opteron processors, Engadget, June , 06/09/worlds-fastest-ibms-roadrunner-supercomputer-breaks-petaflop/ [4]: NVIDIA CUDA Compute Unified Device Architecture, Programming Guide, Version 1.1, Nov , Programming_Guide_1.1.pdf [5]: RS – Intel 2009 Desktop Platform Overview, Sept. 2007, [6]: Smith S.L., Intel Roadmap Overview, IDF 2009, Sept , [7]: Smith S.L., 32nm Westmere Family of Processors, 2009, [8]: Kahn O., Piazza T., Valentine B.: Technology Insight: Intel Next Generation Microarchitecture Codename Sandy Bridge, IDF 2010, extreme.pcgameshardware.de/.../281270d bonusmaterial-pc- games-hardware sf10_spcs001_100.pdf

65 References (2) [9]: Intel Sandy Bridge Review, Bit-tech, Jan. 3 2011,
[10]: 2nd Generation Intel Core Processor Family Desktop, Datasheet, Vol.1, Jan. 2011, [11]: George V., Piazza T., Jiang H., Technology Insight: Intel Next Generation Microarchitecture, Codename Ivy Bridge, IDF 2011, SPCS005 [12]: Athow D., Picture : Ivy Bridge vs Sandy Bridge GPU Die Sizes Compare, ITProPortal, April , bridge-gpu-die-sizes-compared/ [13]: AMD Completes ATI Acquisition and Creates Processing Powerhouse, Oct , [14]: AMD Torrenza and Fusion together, Metal Ghost, March , torrenza-and-fusion-together [15]: Rivas M., AMD 2007 Financial Analyst Day Presentation, Dec [16]: AMD Financial Analyst Day 2008, Nov , [17]: Hruska J., AMD Fusion now pushed back to 2011, Ars Technica, Nov ,

66 References (3) [18]: Intel cans 45nm “Auburndale” and “Havendale” Fusion CPUs!, Jan , and-havendale-fusion-cpus/ [19]: Wikipedia, Turion, [20]: Foley D., AMD’s „LLANO” Fusion APU, Hot Chips 23, Aug , HC Llano-Fusion-Foley-AMD.pdf [21]: AMD A-Series APU, EMEA Press Call, June , [22]: Kirsch N., AMD Llano A-Series APU Sabine Notebook Platform Review, Legit Reviews, June , [23]: Chiappetta M., AMD A Llano APU and Lynx Platform Preview, Hot Hardware, June , Platform-Preview/?page=2 [24]: Walrath J., AMD, Vishera, and Beyond: New Design Philosophy Dictates a Faster Pace, PC Perspective, July , Beyond-New-Design-Philosophy-Dictates-Faster-Pace/How-Does-Vishera [25]: Wasson S., AMD's A M 'Trinity' APU reviewed, Tech Report, May ,

67 References (4) [26]: Paul D., Meet the new AMD APUs Series A-2nd generation “Trinity”, TechNews, May , [27]: OMAP 5 Mobile Applications Platform, Product Bulletin, Texas Instruments, 2011, [28]: Hibben M., Texas Instruments and the Big Chip Maker Anachronism, Nov , anachronism/16680/ [29]: Shimpi A.L., AMD A K & A8-5600K Review: Trinity on the Desktop, Part 1, AnandTech, Sept , 5800k-a8-5600k-review-part-1 [30]: Bates B., Frey W., Goodey S., AMD “Kabini” APU SOC, Hot Chips 25, Aug. 2013, epub/HC Kabini-APU-Bouvier-AMD-Final.pdf [31]: SKYMTL, Under the Hood: Trinity’s Architecture, May 14, 2012, trinity-going-mobile-new-apu-4.html [32]: Singhal R., “Next Generation Intel Microarchitecture (Nehalem) Family: Architecture Insight and Power Management, IDF Taipeh, Oct. 2008, published/sessions/TPTS001/FA08%20IDFTaipei_TPTS001_100.pdf [33]: Shimpi A.L., Intel Iris Pro 5200 Graphics Review: Core i7-4950HQ Tested, AnandTech, June , review-core-i74950hq-tested

68 References (5) [34]: Von Holzbauer F., Kugler A., Neue Intel-Architektur mit Grafik-Fokus, Chip Online, June , PCs_ html [35]: Brown M., Intel lifts the veil on Haswell graphics, PC World, May , [36]: Scansen D., Intel Launches Next Generation of Microprocessors, Engineering, June , 5838/Intel-Launches-Next-Generation-of-Microprocessors.aspx [37]: Goto H., AMD CPU Transition, 2011,

69 Köszönöm a figyelmet!

70 3.2.6 AMD’s Piledriver-based Trinity desktop APU line (6)
Trinity’s Unified North Bridge []

71 GNB: Graphics North Bridge
RMB: Radeon Memory Bus

72 Trinity Unified North Bridge

73 http://www. hardwarecanucks

74 The links between each section of the APU follow in the same footsteps as the previous generation but AMD has refined certain interconnects with the goal of speeding up information transfers. The AMD Fusion Compute Link is still considered to be a medium bandwidth connection which manages the complex interaction between the onboard GPU, the CPU’s cache and the system memory. Unlike in the past, AMD has finally refined this interconnect, giving the GPU direct access to a coherent memory space while the CPU can now directly access the GPU’s dedicated framebuffer if needed. This is one of the primary reasons why Trinity’s theoretical data throughput has jumped from 572 GFLOPS to 736 GFLOPS. The Radeon Memory Bus on the other hand is the all-important link between the onboard graphics coprocessor and the primary on-chip memory controller. Rather than acting like a traffic cop (a la Fusion Compute Link) which tries to direct the flow of information, this memory bus is all about the GPU having unhindered high bandwidth access to the system’s memory controllers. In the previous generations of AMD IGPs, before Llano came around, the Northbridge’s graphics processor had to jump through a series of hoops before gaining access to onboard memory which is partially why 128MB of “SidePort” memory was sometimes added. However, the APU’s single chip, all in one solution allows for the elimination of many potential bottlenecks.

75 Trinity This unit adds virtual address access discrete graphics, allowing an external GPU to directly access the same virtual address space as the CPU through page tables. As you can imagine, this is a key part of the programming model for AMD’s Heterogeneous Systems Architecture (HSA).