S7 clones are "ten times faster"

A range of PLCs that are compatible with Siemens S7 controllers, but are up to ten times faster, made its UK debut at the recent Drives & Controls Show.

The Speed7 PLCs, made by a German company called Vipa, use the same Step7 programming language as S7 controllers, and are compatible with S7 peripherals. The PLCs, which come in a choice of DIN-rail, backplane or PCI mounting formats, use a modular memory system that allows users to buy enough memory (from 64kb to 16Mb) for their application. If they later extend the application, larger memory cards can be installed. The cards can store source code, programs and firmware updates.

Another facility on some models is an ultra-fast parallel bus which supports high-speed digital and analogue inputs for precision applications such as registration. Various combinations of modules can be used simultaneously on the high-speed bus and on the standard serial bus.
The Speed7 PLCs have a cycle time of 100┬Ás and can process more than 50,000 instructions in less than 1ms, making them at least four times faster than Siemens' S7-416 PLC. According to Mark Jones, who represents Vipa in the UK, independent tests have shown that, on some measures, the Vipa PLCs are up to 70 times faster than their Siemens counterparts. Details of the tests can be found on the Speed7 Web site.
Vipa was founded in 1985, originally to make hardware for Siemens. It then started to produce its own Siemens-compatible PLCs which led Siemens to launch a series of legal challenges. According to Jones, they were all dismissed.