再加上 480x640x16bits = 614,400 (我相信應該沒有人會為了達到真的 18bit LCD 而用 24 or 32bpp)
所以也沒法用 PXA270 裡頭的 SRAM 而只能用 SDRAM 來當 frame buffer
假設 refresh rate 是用 60Hz (實際要看 panel spec.)
614,400 x 60 = 35 MB/s 的 throughput
PXA270 的 SDRAM 是跑 104MHz 以 burst mode 在 access 來看
104 x 32 bits = 416MB/s (這是 Burst access 的理論值 實際上沒法達到 而且也會被其它 東西 像 Flash, CF card 等東西消耗掉部份頻寬)
但為了 維持你的 LCD panel 能看得到的基本消費
無論如何就已經先去掉 35MB (差不多是 最高上限的 1/10 了)
有點像是拖著拖油瓶在跑步 只要 panel 開著就會一直存在
這對整體的 performance 有滿大的影響
除了 Graphic 會變差
其它部份 像是 Storage IO, memory access 都有一定的影響
Ti的OMAP750/850是解决方案的面孔而出现的，
OMAP750和OMAP850也是德州仪器（TI）最高端的GSM解决方案，
两者之间的差别就是OMAP850支持即将到来的EDGE网络，OMAP750不支持。
OMAP850是一个高度集成的解决方案，里面集成了除去RF/TR之外的所有功能，
这就使得最终安放在电路板上的芯片大大减少，
同时产生硬件问题的几率也就随之降低，
手机厂商的布线也会更加合理，
模块与模块件的距离随之增大，相互的干扰也就会减小。
而从频率上看，850集成的ARM926TEJ核心的频率仍然维持在了195MHZ，
ARM926TEJ是一个主频为200MHZ的ARM处理器，
一级缓存为24K，其中16 kB I-cache; 8 kB D-cache，
并且内置了JAVA程序硬件加速器
可以使得这款195MHz的处理器在很大程度上增强手机的多媒体处理和表现能力。
和828+采用的Intel处理器的解决方案相比，OMAP 850由于主频较低，
所以在执行一些大的工具软件时反应比较慢，尤其是在运行多线程程序的时候。
838动态的视频录制能力比828+则有所下降，
其可以支持最大分辨率为176X144像素的视频录像，
而828+则可以拍摄320X240像素的视频录像
以上資料摘錄自 http://www.m-buy.net/info/open.asp?forevernetid=1096&title=?c=
這一篇評測說的很詳細大家可以去看看.
ARM926TEJ是一个主频为200MHZ的ARM处理器，
一级缓存为24K，其中16 kB I-cache; 8 kB D-cache，
并且内置了JAVA程序硬件加速器
OMAP850 Features:
Low-Power, High-Performance CMOS Technology
Low-voltage 130 nm technology
1.1 - 1.5V cores, 1.8 - 2.75V IO
Extremely low power consumption: less than 10 µA in standby mode
Split power supplies for application processing, digital baseband and real-time clock enable precise control over power consumption
Optimized clocking and power management: Only two clocks required at 13 MHz and 32 kHz
ARM926TEJ Core Subsystem
ARM926EJ-S V5 architecture up to 200 MHz (maximum frequency)
16 kB I-cache; 8 kB D-cache
Java acceleration in hardware
Multimedia instruction set architecture (ISA) extension
EDGE Digital Baseband Subsystem
384 K-bytes internal SRAM
E-OTD and TTY support
Quad vocoder with EFR, FR, HR, AMR
GSM ultra-low power device (ULPD)
SIM interface
Application Subsystem
Supports all leading operating systems
DMA with 4 physical and 17 logical channels and a dedicated 2D graphics engine
Programmable GPIO keyboard interface
54-Mbps WLAN interface
Security acceleration in hardware:
Secure bootloader
48 kB of secure ROM
16 kB of secure RAM
Hardware acceleration for security standards and random number generator
Unique die ID cell
Third-party Security software library
Enhanced audio controller (EAC)
Comprehensive memory controller for interfaces to:
128 MB of mobile SDRAM
256 MB Flash
NAND Flash controllers
1.6 Mb ISRAM
SD/MMC/SDIO interface
Enhanced Trace Module for debug
LCD controller
uWire
SPI
1-wire and HDQ interface
Bluetooth data/audio interface
USB On-the-Go
Two high-speed 3.68 MHz UARTs
Fast IrDA (FIR)
Two 32-bit timers
Parallel camera port
Programmable three-color LED pulse generation
I²C master/slave controller
SmartCard interface
http://focus.ti.com/general/docs/wtbu/wtbuproductcontent.tsp?templateId=6123&navigationId=12000&path=templatedata/cm/product/data/omap_850
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intel pxa270
Features and Benefits
Intel XScale® Technology Highly scalable core up to 520 MHz
Embedded Packaging 23x23 mm with 1.0 mm ball pitch
13x13 mm with 0.5 mm ball pitch also available
Extended Temperature Range –40°C to 85°C ambient temperature range available
Product Life Cycle Anticipated five-year life cycle.1
Incredible Multimedia Familiar Intel® Wireless MMX™ technology instructions designed for high-performance multimedia, 3-D games and advanced video.
Advanced Camera Interface Intel® Quick Capture technology supports 4+ megapixel cameras for capturing digital images, video and low-power, real-time previews.
Enhanced LCD Controller Dual-panel LCD with up to 24-bit color. Hardware color space conversion with 256 KB of on-chip SRAM for faster video. Two overlays reduce LCD bandwidth. Integrated Intel Quick Capture technology enables fast video preview.
Reduced Power Consumption Wireless Intel SpeedStep® Power Manager technology with five low-power modes can change frequency and voltage dynamically. Wireless Intel SpeedStep Power Manager software enables built-in, intelligent power management.
Fast Access to Wireless Data Intel® Mobile Scalable Link provides up to 416 Mbps link between communications and applications processors.
Large Peripheral Set USB Host/Client
USB OTG
4-bit SD I/O
MMC/SDCard
Memory Stick
USIM card interface
Keypad controller
Memory Interface 100 MHz memory bus supports a variety of 1.8 V, 2.5 V, 3.0 V and 3.3 V memory.
1 Intel anticipates providing support for the Intel® PXA270 processor for a minimum of five (5) years from launch, pending sufficient, continued customer demand and other market conditions and factors. If and when Intel decides to no longer provide support for these products, we will follow our standard product discontinuance notification guidelines of six months to place last time orders and an additional six months to take delivery of the product.
http://www.intel.com/design/embeddedpca/applicationsprocessors/302302.htm
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優點:
整體來說 使用OMAP 850的 838
設計較容易,
成本較低,
硬體故障率低, 生產良率高,
較省電,
有JAVA加速功能,
便宜.
使用 INTEL PXA 270 的手機 818,828
跑的快 416Mhz ,
2d,3d 加速功能,
多媒體方面表現較好.
缺點:
--- OMAP 850
計算速度慢
--- INTEL PXA 270
硬體複雜, 開發不易
硬體故障率高
秏電,
cpu 溫度高,
整體機器成本較高.
其實OMAP 850 的原先設計目的應該是 通用化的智能手機CPU, 讓智能手機手機的成本可以降的更低, 可是衣DOPOD的定價來看用OMAP 850代替intel pxa270 反而變成了她們撈錢的工具, 奇怪的是各網站的評比好像都說 838 跑起來跟 828 差不多,
416Mhz 跟 196Mhz 怎會差不多呢??????
838定價 2萬多實在是坑人啊!(個人意見).
Thumb 在 Windows CE 上很少人用
反而是為了 support Thumb/ARM interworking 讓本 OS and compile 出來的 code 都稍為變慢 (但人是感覺不出 來啦)
本來 OzUpdate 都是 ARMv4 到 Magneto 就變 ARMv4i
J 的話 在 Windows CE 上就更沒人用到了
OS 也沒去 support (基本上 MS 希望你用 .net Frame Work)
so Java byte code on Windows CE 還是都靠 software based JVM 較多.
另外 L1 cache 影響也是很大
OMAP 850 只有 16K D-cache + 8K I-Cache
XScale core 的基本上都是 32K D-cache + 32K I-cache
此外像是 Branch Target Buffer 簡單的管線預測分支
也簡少了一些 branch 時的 stall
不過 TI 的 communication, DSP 等就比 intel 高明多了
OMAP 做電話算是恰如其份
Intel PXA 系列 到 27x 才比較進的了 Phone 的世界
junada2003 wrote:
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優點:
整體來說 使用OMAP 850的 838
設計較容易,
成本較低,
硬體故障率低, 生產良率高,
較省電,
有JAVA加速功能,
便宜.
使用 INTEL PXA 270 的手機 818,828
跑的快 416Mhz ,
2d,3d 加速功能,
多媒體方面表現較好.
缺點:
--- OMAP 850
計算速度慢
--- INTEL PXA 270
硬體複雜, 開發不易
硬體故障率高
秏電,
cpu 溫度高,
整體機器成本較高.
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