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HyperTransport: A High-speed Bus Without Detours

AMD's Athlon 64 Has Arrived: the Athlon 64 FX and Athlon 64 (and Intel's P4 Extreme)
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Unlike all Intel CPUs, which communicate with the Northbridge via a regular parallel FSB, AMD's Hammer relies on a HyperTransport interface. The serial interface with a variable bitrate allows the SledgeHammer to attain a data transfer rate of 3.2 GB/s - in both directions simultaneously. This results in a total bandwidth of 6.4 GB/s. By comparison, the Pentium 4 with 533 MHz FSB allows a maximum data throughput of 3.97 GB/s - but not in both directions simultaneously. The bandwidth of the serial interface is designed to be flexible. AMD gives the server version of the Hammer three HyperTransport ports. The entire data traffic of the Hammer processor runs through the HyperTransport interface and the integrated memory controller. In order to let the neighboring CPU gain direct access to its system memory, the Hammer uses the XBAR switch. For commands and addresses, the XBAR switch has further 64 bit buses available.

Athlon 64/FX: Five Different Modes Of Operation


The five different modes of the AMD 64/FX.

Depending which bits are set in the LME register, the processor works in one of the operating modes depicted here. This ensures backwards compatibility.

Register: 32 Bit & 64 Bit

Although it sounds like significantly less than the 64 bits one might expect from the name, the x86-64 comes with a 40 bit wide physical address space and a 48 bit wide virtual address space. This limits the system memory to 1 TB (1024 GB). New in Hammer: the x86-64 architecture extends the 32 bit register of the IA-32 processors to 64 bit. With applications that run in legacy or compatibility modes, the Hammer can continue to use only the eight conventional 32 bit wide registers EAX, EBX, ECX, EDX, EBP, ESI, EDI and ESP (see graphic above). If the processor works in 64 bit mode, then the x86-64 architecture extends these eight registers via the "R" prefix to 64 bit. The extended registers are then named RAX to RSP. In addition, in 64 bit mode, the Hammer can access another eight GPRs (General Purpose Registers) R8 to R15, which are also 64 bit wide each. For floating point calculations, the eight 128 bit wide SSE registers have been doubled with XMM8 to XMM15. Once again, only the 64 bit mode profits from this.

  Athlon XP Athlon 64 (FX)
Operating Mode 32 bit Mode 32 bit Mode (Legacy or Compatibility Mode) 64 bit Mode
GPRs 8x (32 bit) 8x (32 bit) 16x (64 bit)
SSE registers 8x (128 bit) 8x (128 bit) 16x (128 bit)
MMX registers 8x (64 bit) 8x (64 bit) 8x (64 bit)
x87 registers 8x (80 bit) 8x (80 bit) 8x (80 bit)
The Athlon 64 (FX) presents the operating system with the same number of registers as the old Athlon XP when operating only in 32 bit mode. More registers are only available in 64 bit mode. Enhanced performance is therefore only possible if the memory interface is reworked.
Summary
  1. A New World Order: The Athlon 64 FX And Athlon 64 Vs. The P4 Extreme
  2. A New World Order: The Athlon 64 FX And Athlon 64 Vs. The P4 Extreme, Continued
  3. A New World Order: The Athlon 64 FX And Athlon 64 Vs. The P4 Extreme, Continued
  4. Four Different CPUs With One Design
  5. Four Different CPUs With One Design, Continued
  6. Chipsets & Mainboards: Socket 754 Vs. Socket 940
  7. Chipsets & Mainboards: Socket 754 Vs. Socket 940, Continued
  8. Video 10 To Download: Athlon 64 FX-51 Vs. Athlon 64 Vs. P4 3.2 Extreme
  9. Athlon XP-64 Core: 95 Percent Athlon
  10. Athlon XP-64 Core: 95 Percent Athlon, Continued
  11. HyperTransport: A High-speed Bus Without Detours
  12. Socket 462 Gets Replaced: Sockets 745 And 940/939
  13. Fab30 Dresden Yield: 73 Athlon 64 CPUs Per Wafer!
  14. All AMD And Intel Processors At A Glance
  15. Rough Going - Hardware In The Test Panel
  16. Asus P4C800-E Deluxe: Board Revision 1.02, BIOS 1011 Beta 006
  17. Asus SK8N: Board Revision 1.03, BIOS 1003 Beta 003 (NVIDIA Settings)
  18. MSI MS-9130: Board Revision 1.0, BIOS 1.0BD
  19. General Hardware: Now More Hard Drive Performance
  20. AMD Test Platforms At A Glance
  21. Test Configuration And Special Features
  22. Sysmark 2002: Why Use Obsolete Applications?
  23. Benchmarks Under Windows XP - UPDATED
  24. SPECviewperf 7.1
  25. OpenGL Games: Serious Sam
  26. OpenGL Games: Wolfenstein Enemy Territory
  27. Synthetic: 3D Mark 2001 SE
  28. Games: Comanche 4
  29. Games: Unreal Tournament 2003
  30. Games: Splinter Cell
  31. Games: Warcraft III - The Frozen Throne
  32. Synthetic: 3D Mark 2003
  33. Game: X2 - The Threat Rolling
  34. Game: Gun Metal
  35. Games: AquaMark3
  36. MPEG Encoding: Main Concept MPEG Encoder
  37. MPEG-Encoding: Pinnacle Studio 8.8
  38. MPEG-Encoding: Xmpeg & Divx 5.1 Pro
  39. MPEG-Encoding: Windows Media Encoder 9
  40. MPEG-Encoding: MS Movie Maker 2
  41. Magix MP3 Maker 2004 Diamond
  42. Lame MP3 Encoder
  43. Steinberg Nuendo 2
  44. Sysmark 2002
  45. Winrar 3.2
  46. Newtek Lightwave 7.5
  47. Cinema 4D XL 8.1
  48. Seti@home 3.03
  49. 3D Studio Max 5.1
  50. Mathematica 5
  51. PC Mark 2002 Pro
  52. SiSoft Sandra Max 3
  53. Heat Protection: Now From AMD, Too
  54. Summary: The P4 3.2 EE Wins 32 Times, The Athlon 64 FX-51 15 Times - An Uncertain 64 Bit Future For AMD
  55. Summary: An Uncertain 64 Bit Future For AMD, Continued
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