Buses de Datos

Tipos de Bus SCSI

 
Name         | Standard      | BusWidth | Signal | Bus   | Throughput
Regular/SCSI | SCSI-1        | N-8bits  | SE/HVD | 5Mhz  | 5MB/s    
Wide-SCSI    | SCSI-2        | W-16bits | SE/HVD | 5Mhz  | 10MB/s   
Fast-SCSI    | Fast/SCSI-2   | N-8bits  | SE/HVD | 10Mhz | 10MB/s   
FW-SCSI      | Fast/SCSI-2   | W-16bits | SE/HVD | 10Mhz | 20MB/s   
U-SCSI       | F-20/SCSI-3   | N-8bits  | SE/HVD | 20Mhz | 20MB/s   
UW-SCSI      | F-20/SCSI-3   | W-16bits | SE/HVD | 20Mhz | 40MB/s   
U2-SCSI      | F-40/SCSI-3   | N-8bits  | LVD/SE | 40Mhz | 40MB/s   
U2W-SCSI     | F-40/SCSI-3   | W-16bits | LVD/SE | 40Mhz | 80MB/s   
U3/U160-SCSI | F-80/SCSI-3*  | W-16bits | LVD    | 40Mhz | 160MB/s  
U320-SCSI    | F-160/SCSI-3* | W-16bits | LVD    | 80Mhz | 320MB/s  
 
Name    | Standard     | Bus   | Clocking | MTransfers/s | Narrow | Wide
Regular | SCSI-1       | 5Mhz  | Single   | 5            | 5MB/s  | —
Fast    | Fast         | 10Mhz | Single   | 10           | 10     | 20MB/s
Ultra   | Fast-20      | 20Mhz | Single   | 20           | 20     | 40
U2      | Fast-40      | 40Mhz | Single   | 40           | 40     | 80
U3/U160 | Fast-80(DT)  | 40Mhz | Double   | 80           | —     | 160
U320    | Fast-160(DT) | 80Mhz | Double   | 160          | —     | 320
 
*/DT=Double Transfer, F=Fast, U=Ultra, N=Narrow (8bits), W=Wide (16bits)
 
Para conectores Narrow (8bits) el cable es del tipo A/50pins y para Wide (16bits) P/68pins.
Los terminadores para señales SE debe ser Activo o FPT. para HVD o LVD un terminador del tipo HVD o LVD respectivamente. Para el bus SCSI-1 se puede usar Terminador Passive.
 
Here are the different types of SCSI termination:
 
-Passive Termination: This is the oldest, simplest and least reliable type of termination. It uses simple resistors to terminate the bus, similar to the way terminators are used on coaxial Ethernet networks. Passive termination is fine for short, low-speed single-ended SCSI-1 buses but is not suitable for any modern SCSI speeds; it is rarely used today.
-Active Termination: Adding voltage regulators to the resistors used in passive termination allows for more reliable and consistent termination of the bus. Active termination is the minimum required for any of the faster-speed SE (single-ended) SCSI buses.
-Forced Perfect Termination (FPT): This is a more advanced form of active termination, where diode clamps are added to the circuitry to force the termination to the correct voltage. This virtually eliminates any signal reflections or other problems and provides for the best form of termination of a single-ended SCSI bus.
-High Voltage Differential (HVD): Buses using high voltage differential signaling require the use of special HVD terminators.
-Low Voltage Differential (LVD): Newer buses using low voltage differential signaling also require their own special type of terminators. In addition, there are special LVD/SE terminators designed for use with multimode LVD devices that can function in either LVD or SE modes; when the bus is running single-ended these behave like active terminators.
 
 


Tipos de Bus PCI

   lado exterior
(a)     (b)     (c)
 +       +       +
 |       |       |
 |       |       +
 |       |       |
 |       |       |
 +       +       |
 |       |       |
 +       +       +      –
         |       |
         |       |
         +       +

(a)regular   | (b)wide      | (b)fast/wide | (c)fast/wide/3.3V
32bits/33MHz | 64bits/33MHz | 64bits/66MHz | 64bits/66MHz
1Gbps        | 2.1Gbps      | 4.3Gbps      | 4.3Gbps
 
 

Tipos de Memorias

 

SDRAM: Synchronous Dynamic Random Access Memory, DIMM-168 pines (1 transferencia por ciclo de reloj)
PC66, PC100, PC133 (Mhz)
DDR: Double Data Rate (Prefetch 2bits, 2.5V) DIMM-184 pines (2 transferencias por ciclo de reloj)
DDR-xxx indica la velocidad de reloj efectiva, mientras que PC-xxxx indica el ancho de banda teórico (aunque suele estar redondeado al alza).
 
PC-1600: DDR-200, 100 MHz 1,6GB/s
PC-2100: DDR-266, 133 MHz 2,1GB/s
PC-2700: DDR-333, 166 MHz 2,6GB/s
PC-3200: DDR-400, 200 MHz 3,2GB/s
PC-3500: DDR-433, 217 MHz 3,5GB/s
PC-3700: DDR-466, 233 MHz 3,7GB/s
PC-4000: DDR-500, 250 MHz 4,0GB/s
PC-4400: DDR-550, 275 MHz 4,4GB/s
PC-4800: DDR-600, 300 MHz 4,8GB/s
DDR2: Double Data Rate (Prefetch 4bits, 1.8V), DIMM-240 pines (4 transferencias por ciclo de reloj)
El ancho de banda se calcula multiplicando la velocidad de reloj por ocho, ya que la DDR2 es una memoria de 64 bits, hay 8 bits en un byte, y 64 es 8 por 8.
 
PC2-3200: DDR2-400, 100 MHz, 3,200GB/s I/O Clock 200 MHz.
PC2-4200: DDR2-533, 133 MHz, 4,267GB/s I/O Clock 266 MHz.
PC2-5300: DDR2-667, 166 MHz, 5,333GB/s I/O Clock 333 MHz.
PC2-6400: DDR2-800, 200 MHz, 6,400GB/s I/O Clock 400 MHz.
 
Su punto en contra son las latencias en la memoria más largas (casi el doble) que en la DDR.
DDR3: Double Data Rate (Prefetch 8bits, 1.5V) futuro 2008
PC3-6400: DDR3-800,  100 MHz, 6.40 GB/s I/O Clock 400 MHz
PC3-8500: DDR3-1067, 133 MHz, 8.53 GB/s I/O Clock 533 MHz
 
GDDR3 (Graphics Double Data Rate, version 3) no es DDR3

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