Multi level indirection6/29/2023 Was responsible for the substrate design changes that extended the BPC/EMC/IOC hybridĪfter first writing a Fortran program on an HP2115 to analyze NMOS II artwork for design For the 9845 actually only 6 of the 16 possible AEC lines were utilized outside the processor, so the effective 9845 address space was in total limited to 64 memory blocks.ĭyke Shaffer was a late addition to the development of the HP5 series and Later the address space of the hybrid processor was even more extended by a fourth NMOS chip, the address extension chip (AEC), which expanded the address space to (in principle) 65,536 memory blocks of 32 KWords each (= 4 Gigabytes!!!), and provided a very flexible kind of bank switching scheme. The main change for the 9845 system with respect to the 9825 system was that the most significant address bit (the 16th bit) was no longer used for multi-level indirection addressing, but the address space was extended to 64 KWords (full 16 bit address space). Almost the same type was already in use with the common 9825 series, as well as in some measuring equipment like the HP3585A spectrum analyzer (1978). The 9845 series were not the first systems which used this hybrid processor. Note that the BASIC interpreter cuts the exponent to a range from -99 to +99. Unlike contemporary processors, but in the tradition of HP's calculators, all floating point numbers were represented by BCD mantissa and binary exponent, not in complete binary representation. The EMC was a quite powerful floating point processor. Later HP introduced a modified high-performance version of the LPU, which was built on a custom bit-slice processor design, but still physically and electronically compatible to the original processors - the "hybrid processors". In fact, those processors were the first 16-bit microprocessors ever (as well as the 2116A had been one of the first 16-bit minicomputers before). So, much of the existing know-how and development environment of the 211x series could be recycled for the new processors. The processor design went back on a very early minicomputer design, that of HP's first computer ever, the 2116A, which was transferred into a microprocessor design. The logical processing unit or LPU did execute all user programs, including BASIC programs and binary software modules.įor most systems, both processors were identical. One processor, the peripheral processing unit or PPU was responsible for all the I/O processing, like serving keyboard interrupts, writing data to the CRT display, or handling other peripheral I/O. All 9845 were controlled by two processors working in parallel.
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