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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDRjtmAiNpo5mK5N3d7QwZ

content/history/zilog-z8000.md

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+---
+title: ZILOG Z8000
+date: '1979-04-01'
+years:
+- '1979'
+topics:
+- Hardware
+params:
+  when: APRIL 1979
+  oc_id: 52
+  source:
+    url: https://web.archive.org/web/20221215134357/http://www.old-computers.com/history/detail.asp?n=52
+    date: '2022-12-15'
+---
+
+![](/media/history/images/timeline_0479_z8000_2.jpg)
+
+The Z8000 CPU series was introduced in early 1979, between the launch of the Intel **8086** (April 1978) and the Motorola **68000** (September 1979).
+
+Two versions were released, the **Z8001** capable of addressing 8 MB of memory via segment registers, and the **Z8002** which could only address 64 KB. Like the Zilog Z80, the Z8000 included built-in DRAM refresh circuitry. An optional **Z8010** MMU (Memory Management Unit) co-processor allowed up 48 MB of memory to be addressed.
+
+Internally the Z8000 chip held 17500 transistors in NMOS design, and it had sixteen 16 bit registers which could be extremely flexibly used. The programmer could see them as 16 8-bit, 16 16-bit, 8 32-Bit, or 4 64-bit registers. All registers were general-purpose registers, although registers 14 and 15 were usually used as stack segment and pointer. Among its 110 instructions and 13 addressing modes, the Z8000 also offered 32-bit multiplication and division instructions.
+
+There was both a user mode, for programs, and a supervisor mode, for the operating system. The user mode prevented access to potentially dangerous things such as interrupt handling.
+
+Despite these attractive features the Z8000 was not very fast and suffered from some internal bugs. It was thus never very popular and was surpassed a few months later by the Motorola 68000 and later, by the Intel 286.
+
+The Z8000 can be found in some rare but well-known computers though, such as the Olivetti M20 and M40, and the Unix-based Commodore 900. Some third parties also manufactured the Z8000 including AMD, Hitachi and Sharp.
+
+The Z8000 was followed in 1986 by the **Z80000**, an amazing 32 bit processor whose features (pipeline, cache memory) would not appear until six years later in Intel processors.\
+The Z8000 is still alive nowadays with the Z16C00, a CMOS version mainly used in embedded applications.
+
+---
+
+**Mike Throm's** memories:\
+I worked in Zilog's system division for 6 years. The primary goal was to design systems using Zilog processors. One of the notable leaders of Zilog's system engineering group was **Judy Estrin** who lead the effort to develop an ethernet like LAN product for Zilog, who then went on to other ventures like Bridge Communications (acquired by 3Com), NCD, and Precept.\
+Zilog also designed a UNIX "supermicro" system called the S8000 initally based on the Z8000, then the Z80000 with a UNIX based OS called Zeus.\
+Like most silicon valley firms of the time, we took pride in what we did and spent long hours to develop products. 60 - 80 hours per week during peak development cycles were common. Also, because almost all of us were under 30, weekend parties and "beer busts" were also common between development cycles.\
+Many S8000 units were sold to the IRS; however, the system side of the business never took off and was eventually closed down around 1985.
+
+**Peter Sandilands** adds:\
+The Z8000 was used in a quite successful line of computers from Onyx Inc (California). Originally built for AT&T they ran Unix V7 and Interactive Systems IS/1.\
+The architecture continued into the mid '80s and ran Sys III. Sold as general purpose business computers they had the option of a number of bundled business packages using software such as Quadratron word processor. New Onyx C8002s were still being sold in 1986!
+
+![](/media/history/images/timeline_0479_z8000_1.jpg)