The Bus Pirate can program flash chips with flashrom and debug JTAG devices with OpenOCD, but it doesn’t do these things very fast. It was designed for human-speed interaction. The Bus Pirate is a good way to learn an EEPROM chip, but you eventually integrate the chip in a real circuit with actual code. In the same way, the Bus Pirate is a good first-taste of JTAG or ROM programming, but if you do it regularly you’ll want something faster with more features.
The Bus Blaster is our solution, a device just for high-speed device programming and debugging. We’re currently designing the Bus Blaster in the forum. It will be a USB 2.0 JTAG/SPI/UART device based on the FT2232H. The FT2232H is a USB->serial converter like the FT232R currently used on the Bus Pirate, but is also has a module called an MPSSE that can be configured for high-speed JTAG and SPI modes. It won’t have a terminal interface or be programmable like the Bus Pirate, this will be a specialized programming/debugging device intended for some upcoming ARM-based projects.
Why not use the FT2232 on the Bus Pirate? The PIC on the Bus Pirate uses a serial UART to communicate, it’s converted to USB via the FT232 chip (note only one 2). The top speed is limited by the PIC UART, and not the USB connection. The FT2232 is bigger, more expensive, and requires more support components, but wouldn’t improve the Bus Pirate speed. The most direct way to make the Bus Pirate faster would be an integrated USB microcontroller.
Image from the flashrom project.