computer bus speeds explained - how fast is your system bus?
 

 

 

 

 
Explaining Computer Bus Speeds
Now that you have learned about network speeds (see article) we can examine the common ways network interfaces and other devices link into the computer.  By examining the maximum throughput of various interfaces like ISA, PCI, and USB, we can determine what network interfaces are inappropriate for certain bus's.  By comparing the speeds in this article with the network speeds article, you will get a good idea of how fast devices talk to your computer.
Bus Speed Chart
BusName Width Speed*/Sec
SCSI-1   5 Mbytes
ISA 8bit, 8Mhz 8 Mbytes
SCSI-2   10 Mbytes
PCMCIA    16 bit, 10 Mhz 20 Mbytes
IDE DMA33   33 Mbytes
Ultra2 SCSI   40 Mbytes
IDE DMA66   66 Mbytes
PCCard    32 bit, 33 Mhz 132 Mbytes
PCI 2.0    32 bit, 33 Mhz 132 Mbytes
PCI 2.1    64 bit, 33 Mhz 264 Mbytes
PCI 2.2 64 bit, 66 Mhz 528 Mbytes
     
Serial 1 Bit 115 kbit
Parallel Port 8 Bit 115 kbit
USB 1.0  (standard USB) 1 Bit 1.5 MBytes
12 Mbits
Firewire (IEEE 1394)   Serial  12.5-50 MByte
100-400 Mbit
USB 2.0  Serial  60 MBytes
480 Mbit
Firewire (IEEE 1394b) Serial  25-100 MBytes
200-800 Mbit
*Speed is a theoretical maximum.  Various buss' have different overheads associated with them
Conclusuions
Ethernet NIC's and the ISA bus :  Some manufacturers actually sell 100Mbps Ethernet cards for an ISA BUS.  As you can see from the chart above, the ISA bus will max out at 8MBytes/sec.  8MBytes/sec is the theoretical maximum you could ever get from a 100Mbps LAN card plugged into the ISA bus! 

 


 

 

 


 
 
Site last updated: Monday, July 26, 2004 12:12 PM