Future Upgrade Considerations: T9000 vs. TMS320C40

There are two major contenders in the bracket above the T805 transputer: the Inmos T9000 (next-generation Transputer), and the Texas Instruments TMS320C40 parallel DSP. Both have similar features; the C40 has been available for a longer time (in fact, it was unveiled just one month after our Transputer system had been installed), whereas the T9000 came out a little over a year ago, but is undergoing constant improvement.

The T9000 Transputer

Here is a block diagram showing the T805 vs. T9000 transputer, with important new additions highlighted in yellow. Some useful features are:

• "virtual channels": whereas in the old generation transputer a serial link was limited to holding 2 software channels (one for each dir'n), the current transputer can have an unlimited number of software channels on a single hardware link. It uses packets to send data across them these channels; this packet switching is handled in hardware.
• "transparent routing" A program can send a message from one process on one transputer to another process on another transputer anywhere in the transputer network, without having to worry about which channels it will go through; the routing is done automatically by hardware (an Inmos INSC014 routing device)
• faster links, with 100Mbits/sec full-duplex communication for each link (there are still four links on the chip; however, the T805 has only 20Mbit/sec links).
• an overall 10x increase in speed over the T805
• better software access to scheduling mechanism (good for control system applications!)
• binary compatible with previous transputers

The C40

The TMS320C40 parallel DSP from Texas Instruments has some very attractive features which are not found in the T9000 transputer:

• 6 serial links (two more than the T9000 transputer), with a transfer rate of 20MByte/sec (that's MegaBYTE per sec!)
• 50 MFLOPS performance per processor (increased by adding several in parallel
• hardware support for shared memory between processors; the programmer is no longer confined to a purely distributed memory model. All of the C40's in a system can have access to a shared memory segment.

Unfortunately, the C40's cannot be used with our current transputer motherboard (even though they mount in a motherboard of their own, which is very similar to the TRAM concept -- individual TRAMS are, however, slightly larger than the transputer ones). Also, I am unsure about what kind of analog I/O is available for C40 systems; most likely there is a wide base to choose from, since many more people use the C40 than use the transputer. Anyone looking into a C40 system should make sure analog I/O is tightly coupled to the processor, so that the bottleneck is not the communication between processor and A/D (or D/A). Also, the A/D's should latch and convert all channels simultaneously, as explained in the previous section [link].

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