High-Speed Data Transfer: AGP, HyperTransport, and Parallel Ports

AGP Bus: High-Speed Graphics Interface

The AGP bus was developed to release the occupation of system buses as much as possible when working with the graphics card. Since graphics cards require a significant amount of data, especially when working in 3D, they previously kept buses busy and prevented other peripherals from connecting. The general characteristics for this bus include:

• Speeds are much higher than the peak of the system bus.
• It incorporates DMA (Direct Memory Access).
• It can access main memory for instructions and programs while performing read/write operations.
• It can use main memory as video memory.
• There are no waiting times because it does not have to compete for system buses.

HyperTransport Technology

HyperTransport is a universal communication technology between chips that offers integrated circuits a high-speed, high-performance link. It is a universal connection designed to reduce the number of buses within a system, providing a link for high-performance embedded applications and highly scalable multiprocessing systems. HyperTransport can move data from the processor to other motherboard components up to 48 times faster than the PCI bus. When the 2.0 specification was released, it unveiled three new speeds and definitions to interface with the PCI Express I/O architecture. When integrated into systems, it can reach speeds of 22.4 gigabytes per second, whereas the previous cap stood at 12.8 GB/second.

Parallel Port: Fast Data Interface

The parallel port emerged as a quick alternative to the serial interface, which was the standard for printers and data terminals at the time. This speed increase was due to the Centronics parallel interface, which allowed sending a byte (8 bits) at a time. However, it has the disadvantage of not allowing great distances between the computer and the peripheral.

Parallel Port Operating Modes

1. Unidirectional Mode: Sends data in one direction, from the PC to the printer. It places the byte through port pins and verifies the printer is ready. Supported for compatibility, it uses a FIFO buffer (150 to 500 kb/s).
2. Bidirectional Mode: Communication is bidirectional. To offload functions, the EPP (Enhanced Parallel Port) was introduced, designed for devices other than printers.
3. ECP Mode: Aimed at improving transmission performance for advanced external peripherals. ECP achieves transfer speeds up to 2 MB/s.
4. ECP + EPP Mode: The joining of the two modes, reaching speeds up to 4 MB/s.
5. Nibble Mode: Allows sending data in chunks of up to 4 bits.