Editing Transputer (section)

=== T9000 ===
[[File:T9000LidOff.jpg|alt=Computer chip with lid removed showing silicon die installed at an angle|thumb|T9000 Transputer with lid removed to show silicon die]]
Inmos improved on the performance of the T8 series transputers with the introduction of the ''T9000'' (code-named ''H1'' during development). The T9000 shared most features with the T800, but moved several pieces of the design into hardware and added several features for [[superscalar]] support. Unlike the earlier models, the T9000 had a true 16&nbsp;KB high-speed [[CPU cache|cache]] (using random replacement) instead of RAM, but also allowed it to be used as memory and included MMU-like functionality to handle all of this (termed the ''PMI''). For more speed the T9000 cached the top 32 locations of the stack, instead of three as in earlier versions.
[[File:T9000Wafer.jpg|alt=Silicon wafter covered in a tiled pattern of transistors for processors reflecting sunlight in rainbow patterns|thumb|Uncut silicon wafer of Inmos T9000 transputers]]
The T9000 used a five-stage pipeline for even more speed. An interesting addition was the ''grouper''<ref>Inmos T9000 CPU patent, [http://www.freepatentsonline.com/5742783.html "US patent 5742783"],</ref> which would collect instructions out of the cache and group them into larger packages of up to 8 bytes to feed the pipeline faster. Groups then completed in one cycle, as if they were single larger instructions working on a faster CPU.

The link system was upgraded to a new 100&nbsp;MHz mode, but unlike the prior systems, the links were no longer downwardly compatible. This new packet-based link protocol was called ''DS-Link'',<ref>Inmos DS Link patent, [http://www.freepatentsonline.com/5341371.html "Communication Interface US patent 5341371"]</ref> and later formed the basis of the [[IEEE 1355]] serial interconnect standard. The T9000 also added link routing hardware called the ''VCP'' (Virtual Channel Processor) which changed the links from point-to-point to a true network, allowing for the creation of any number of ''virtual channels'' on the links. This meant programs no longer had to be aware of the physical layout of the connections. A range of DS-Link support chips were also developed, including the ''C104'' 32-way crossbar switch, and the ''C101'' link adapter.

Long delays in the T9000's development meant that the faster load/store designs were already outperforming it by the time it was to be released. It consistently failed to reach its own performance goal of beating the T800 by a factor of ten. When the project was finally cancelled it was still achieving only about 36 MIPS at 50&nbsp;MHz. The production delays gave rise to the quip that the best host architecture for a T9000 was an overhead projector.

This was too much for Inmos, which did not have the funding needed to continue development. By this time, the company had been sold to SGS-Thomson (now [[STMicroelectronics]]), whose focus was the embedded systems market, and eventually the T9000 project was abandoned. However, a comprehensively redesigned 32-bit transputer intended for embedded applications, the ''ST20'' series, was later produced, using some technology developed for the T9000. The ST20 core was incorporated into chipsets for [[set-top box]] and [[Global Positioning System]] (GPS) applications.