==> ggg12345.bbs@ptt.cc (ggg) 提到:
> ※ 引述《FredLu.bbs@bbs.ntu.edu.tw (神之造物必有其因)》之銘言：
> : DMA / IRQ 還算是很 Low Level 的東西吧,
> : DMA 只能做簡單的 data moving,IRQ 只能做 system interruption,
> 是的, 這是很基本的東東.
> : 這種古董老掉牙的 structure 對於先進的 AGP bus 根本沒有用,
> : 講求 3D 繪圖效能的電腦系統,AGP 甚至還允許 GPU 執行自己的
> : micro instruction , 並且 share physical memory,
> : GPU 已經具備多核心電腦的雛型了,NVIDIA 的 GPU 甚至還有 4 piple line
> : 的 micro instrion 處理能力,使用電晶體的數量早就超過 Intel CPU.
> 早期 PC 的顯示卡使用 M6845 controller 取出顯示資料變成 video signal 給
> CRT. X86 cpu 與 video controller 共用 display 記憶體則是使用 dual port
> memory , 各有各的通道. 這段記憶體是特定區域, 通常置於顯示卡上.
> Video Controller 因解析度要求越做越快, 同時也兼負起協助畫圖產生資
> 料的工作(如填色), 她是自備另一個獨立的專用通道來取用顯示資料, 因此用不
> 上 DMA.
根據 Intel 網站上的文件資料, http://www.intel.com/technology/pciexpress/
devnet/docs/pciexpressgraphics1.pdf
Why PCI Express* Architecture for Graphics ?
Introduction
The evolution of PC graphics interconnects has been on a trend where
graphics bandwidth has increased rapidly throughout the years.
In the 90’s the industry has seen a trend where graphics BW has
doubled roughly every 2 years to keep pace with new applications
and support future requirements. In the mid to late 90’s the
Accelerated Graphics Port (AGP) was introduced. This was driven
primarily by 3D applications and the need for more bandwidth and
faster processing for graphics. Through the evolutions of AGP1x -
2x - 4x and 8x we’ve seen the bandwidth double each time. Now there
is another inflection point.
New applications are evolving using photo-realism drive BW demands.
The Digital Home and next generation GUIs are rapidly evolving and
will be driving bigger bandwidth demands for the future. However,
continuing on an evolutionary path with AGP to keep up with current
demands and future requirements, one which is a parallel point to
point interconnect using source synchronous timing, would pose
serious limitations. The existing connector would have to be redesigned
to accommodate lower inductance and capacitance at higher signaling
rates. The timing budget would be significantly reduced with very little
margin. An evolutionary approach to AGP is simply not feasible to
support future demands. What is needed is a new technology that
supports both near and long term platform requirements.
PCI Express is a 2.5 Giga transfers/second serial differential point-
to-point high speed interconnect with added flexibility and scalability
that is intended to replace AGP and PCI over time. PCI Express is this
new technology for graphics, providing enough bandwidth and performance
for the next decade.
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