Offshoots of Sharp’s 4-bit SM5-series microcontrollers were also the dedicated key/lock chips known as “CIC” which were present on the NES, SNES, and N64 for the ostensible purposes of copy protection (though which were more realistically for vendor lock-in). The fact that Sharp were tapped for the Game Boy’s CPU isn’t a coincidence, either, as by the time the Game Boy was in development, Nintendo had a 7-year history of working with Sharp, as the company’s 4-bit microcontroller line (the Sharp SM5x and SM51x) were the basis of all of Nintendo’s “Game & Watch” line of handhelds dating back to 1981. On-board support for DRAM refresh (the ‘R’ register) is not. The ‘shadow’ register file is not present. The opcodes prefixed with a ‘CB’ byte are present, but the remaining prefix instructions (DD, ED, FD) are not. The CPU used in the Game Boy is a Sharp LR35902, which has a number of features in common with the Zilog Z80, but lacks much of what people associate with the Z80 over the Intel 8080. The chip used in the original Game Boy is a fun offshoot of computing history in and of itself. Posted in Retrocomputing Tagged z80 Post navigation Does the world need another Z80 OS? For that matter, does the world need any more Z80 systems? We don’t know about the world, but we can always use them. There is a large list of things to do, so if you have a mind to pitch in, there’s no shortage of ideas to work on. The system calls and general operation will remind you of Linux. The kernel takes about 6K of ROM and 1K of RAM, depending on the configuration. The author wanted a simple OS that wasn’t multithreaded and could live in ROM. You can also try it in emulation mode in your browser if you don’t have a Z80 CPU handy. The work isn’t totally done, nor is the initial target computer - Zeal - but it looks like a great piece of work so far and will be of interest to anyone who has a Z80. The features you expect are there: files, directories, device drivers, a clock, and even memory banking to support up to 16M of memory. You can watch a demo of the open-source OS in the video below.Īs you might expect, the whole system is written in Z80 assembly language. If you have a soft spot for a Z80 computer but want a new operating system experience, try Zeal.
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