IDT 574 Projects

Auto Routed IDT574 design

Plot of Cadence’s Allegro auto router for the IDT574 board.

Several of the 64-bit IDT range of MIPS processors were designed by QED. The local agents in South Africa were really good on support and supplying small quantities for prototypes. MIPS were ahead of PowerPC and ARM during the 1990s in our opinion, particularly for academic articles and the DLX instruction set essentially being in the public domain. Clock speeds were reasonable and the range covered both 32- and 64-bits.

The 32- and 64-bit MIPS devices had few differences from a software perspective. The context switch would obviously have to deal with 8-bytes per register rather than 4-bytes. The floating-point registers were paired in the 32-bit devices, (F0,F1 for double precision) while the 64-bit devices had 64-bit floating point registers that could handle double precision. The memory mapping for the TLB layout was different, but once setup, would be transparent to application programmers. The IDT 3081 which was used for a previous “paper design” had a multiplexed bus, similar to the 64-bit IDT574. There were additional SysCMD lines for generating bus signals.

During the second half of 2000 and the first three months of 2001 we commuted between Port Elizabeth and Pretoria. The contract work was for image processing using DSPs, but we had time in the evenings for speculating with a 64-bit design. The compiler toolchain was functional under 32-bit Linux plus the IDT574 was a fairly basic core—there were no integrated peripherals. The interface between memory would require an ASIC or a FPGA. Galileo Technology, V3 and others made MIPS SysAD/SysCmd interface chips. Algorithmics in the UK was working on a FPGA version. Xilinx published an application note with Verilog for a MIPS interface, so we took the plunge.

Four stages of 64-bit design were attempted. The second and third were during nine months—April to December 2001— of commuting between Port Elizabeth and Stellenbosch (near Cape Town). The fourth effort was to design a board for tracing and real-time research in 2002. None of the designs were commercialised. Looking through some archives, we found some notes on a “MIPS Concept Design for Software Instrumentation” which was dated 2006. We have included the IDT574design.pdf (307 kBytes) here. Minor revisions were done annually.