PC Card Slot Types
ISA
AGP
PCI
PCI-X
PCI-E (PCIexpress)
ISA
ISA, or Industry Standard
Architecture, is an 8bit or 16bit parallel bus system that allowed up 9️⃣ to 6 devices to
be connected to a PC. Virtually all IBM-compatible PCs made before the Pentium were
based on 9️⃣ the ISA (IBM's PC AT) bus. This asynchronous bus architecture uses 16-bit
addresses and an 8-MHz clock and handles a 9️⃣ maximum data throughput of 2 MB/s to 3
MB/s.
ISA is the precursor to PCI. Standing for "Industry Standard Architecture" It 9️⃣ was
common from the early 1980s to the mid 1990s. ISA was a typically inelegant solution
for the time, and 9️⃣ required one to know exactly what one was doing- PnP was rare, even
for so called "ISA PnP" peripherals. In 9️⃣ the end, the combination of flexibility, ease
of use, and greater capability allowed PCI to supersede ISA.
PCI
The PCI bus
architecture 9️⃣ is a processor-independent bus specification that allows peripherals to
access system memory directly without using the CPU. Not only does 9️⃣ this free up the CPU
to service other application calls, but PCI users also can simultaneously acquire data
to memory 9️⃣ and analyze existing data in real time, all while communicating with other
functions on the network.
More importantly, PCI peripherals running 9️⃣ asynchronously can
send data along the 32-bit bus at a rate of up to 132 MB/s or 66 MS/s.
AGP
The
Accelerates 9️⃣ Graphics Port is a high-speed point-to-point channel for attaching a video
card to a computer's motherboard. It was created in 9️⃣ 1997 yet by 2004 was largely
replaced by PCI Express. The primary advantage of AGP over PCI is that it 9️⃣ provides a
dedicated pathway between the slot and the processor rather than sharing the PCI bus.
In addition to a 9️⃣ lack of contention for the bus, the point-to-point connection allows
for higher clock speeds. AGP also uses sideband addressing, meaning 9️⃣ that the address
and data buses are separated so the entire packet does not need to be read to get
9️⃣ addressing information. This is done by adding eight extra 8-bit buses which allow the
graphics controller to issue new AGP 9️⃣ requests and commands at the same time with other
AGP data flowing via the main 32 address/data (AD) lines. This 9️⃣ results in improved
overall AGP data throughput.
PCI-X
PCI-X stands for "PCI-eXtended". PCI-X is a computer
bus and expansion card standard that 9️⃣ enhances the 32-bit PCI Local Bus for higher
bandwidth demanded by servers. It is a double-wide version of PCI, running 9️⃣ at up to
four times the clock speed, but is otherwise similar in electrical implementation and
uses the same protocol.[1] 9️⃣ It has itself been replaced in modern designs by the
similar-sounding PCI Express, which features a very different logical design, 9️⃣ most
notably being a "narrow but fast" serial connection instead of a "wide but slow"
parallel connection.
PCI-X revised the conventional 9️⃣ PCI standard by doubling the
maximum clock speed (from 66 MHz to 133 MHz)[1] and hence the amount of data 9️⃣ exchanged
between the computer processor and peripherals. Conventional PCI supports up to 64 bits
at 66 MHz (though anything above 9️⃣ 32 bits at 33 MHz is only seen in high-end systems)
and additional bus standards move 32 bits at 66 9️⃣ MHz or 64 bits at 33 MHz. The
theoretical maximum amount of data exchanged between the processor and peripherals with
9️⃣ PCI-X is 1.06 GB/s, compared to 133 MB/s with standard PCI. PCI-X also improves the
fault tolerance of PCI allowing, 9️⃣ for example, faulty cards to be reinitialized or taken
offline.
PCI Express
PCIe, or Peripheral Component Interconnect Express, is a computer
expansion 9️⃣ card standard designed to replace the older PCI, PCI-X, and AGP standards.
PCI Express is used in consumer, server, and 9️⃣ industrial applications, as a
motherboard-level interconnect (to link motherboard-mounted peripherals) and as an
expansion card interface for add-in boards. A 9️⃣ key difference between PCIe and earlier
buses is a topology based on point-to-point serial links, rather than a shared parallel
9️⃣ bus architecture.
Bandwidth
Below is a table showing the different buses/card slot
types and their maximum bandwidths:
PCI 132 MB/s AGP 8X 2,100 9️⃣ MB/s PCI Express 1x 250
[500]* MB/s PCI Express 2x 500 [1000]* MB/s PCI Express 4x 1000 [2000]* MB/s PCI
9️⃣ Express 8x 2000 [4000]* MB/s PCI Express 16x 4000 [8000]* MB/s PCI Express 32x 8000
[16000]* MB/s USB 2.0 (Max 9️⃣ Possible) 60 MB/s IDE (ATA100) 100 MB/s IDE (ATA133) 133
MB/s SATA 150 MB/s SATA II 300 MB/s Gigabit Ethernet 9️⃣ 125 MB/s IEEE1394B [Firewire 800]
~100 MB/s*
* Note - Since PCI Express is a serial based technology, data can be 9️⃣ sent
over the bus in two directions at once. Normal PCI is Parallel, and as such all data
goes in 9️⃣ one direction around the loop.
