MIPS Computer Systems Inc - together with its five semiconductor partners - has duly unveiled a third-generation 64-bit RISC, the R4000. The R4000 will be the backbone of the Advanced Compting Environment initiative's next generation of Advanced RISC Computing systems. The 50MHz part, with 1.3m transistors, comes in three guises: the R4000PC, rated at 40 SPECmarks, supports primary on-chip cache and is a 179-pin grid array part targeted at low-cost desktop, low-end server and embedded implementations. The R4000SC, rated at 60 SPECmarks - for uniprocessor applications - comes with secondary cache, and is being offered in 447-pin grid array or land grid array configurations. It's aimed at high-performance desktops and servers. The R4000MC, again rated at 60 SPECmarks, comes with multi-processing features, secondary cache, and is available in 447-pin PGA or LGA packaging. Each has a 64-bit integer processor, 64-bit floating point unit, memory management unit, 8Kb instruction cache, 8Kb data cache, and control and management facilities for secondary cache. MIPS says the 64-bit functions offer full binary compatibility for applications running on its existing 32-bit CPU implementations. At the launch, early versions of ACE's Open Desktop and Windows NT operating systems from Santa Cruz Operation Inc and Microsoft Corp were shown running on the R4000, as was MIPS' own RISC/os Unix implementation. R4000-based ARC systems running Open Desktop and Windows NT will begin to appear after the middle of next year. MIPS' partners, which will manufacture the parts, are Integrated Device Technology Inc, LSI Logic Corp, NEC Electronics Inc, Performance Semiconductor Corp and Siemens Components Inc: thy will be announcing their own price and delivery details. MIPS also has 20 development tools for the R4000, including its C RISCompiler and system programmers pack. The latter includes input-output drivers and is from $8,000. will collaborate with Integrated Device Technology Inc, Santa Clara to do microcontroller versions of the MIPS Computer Systems Inc R3000 RISC CPU.