Break Points
ZiLOG, Redux, Redux, Redux
Jack Ganssle
12/14/2009 1:49 PM EST
ZiLOG capitalized on the Z80's success with a variety of other processors, such as the ill-fated Z800 which was Z80-compatible but offered much higher performance. That part never made it to market. The Z280, though, went into production. Somewhat Z80-compatible it offered cache, a range of on-board peripherals, and 24 address lines. Excessively complex the part suffered from a variety of bugs that ZiLOG never managed to iron out.
At the time a company executive told me it had been manually taped out and the cost to move the design to their current CAD system was prohibitive, so no updates were planned. The part soon became a market failure.
Hitachi, though, upscaled the Z80 into their 64180 which had a primitive on-board MMU that extended the address bus to 20 bits. ZiLOG offered the part under the name Z180, and it gained substantial market share, and is also still available today.
They entered the 16 bit market with the Z8000, a very sophisticated chip, which found a ready niche mostly in the military. Overshadowed by the more or less contemporaneous x86 and 68000, it never reached its full potential despite an orthogonal architecture every engineer loved.
Today the company offers other Z80-like parts which have become somewhat successful. Their Z8, a microcontroller, came out in 1979 and is still alive in updated variants.
Sounds like a success story! Alas, ZiLOG was a perennial money-loser, though they did have a shining moment in the 1990s when sales were as high as $223 million. But sales fell, they filed for bankruptcy in 2001, and have struggled since then, losing money at least every year since 2004 (with the exception of a small profit last year generated entirely by the sale of a part of their business). Sales were $36m last year, which was the low point of a steady stream of declining revenue.
Now Ixys Corporation has offered to buy the company for $62.4m in cash, which is roughly the current valuation of ZiLOG's stock. Having had a close association with Zilog in their pre-camelcase years, I'm happy to see them in this alliance, which can only add strength to their tottering balance sheet, and wish the company future success. Perhaps 35 years from now, in 2044, the Z80 will still be going strong.
Jack G. Ganssle is a lecturer and consultant on embedded development issues. He conducts seminars on embedded systems and helps companies with their embedded challenges. Contact him at jack@ganssle.com. His website is www.ganssle.com.
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vedavis
12/15/2009 9:00 AM EST
"I wonder if any other CPU has had such a long life." - Long Live the 8031!
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BobDJr
12/15/2009 1:54 PM EST
"I wonder if any other CPU has had such a long life." - Intersil is still selling the 1802, which dates back to at least 1976, farther if you consider the 1801.
(BTW, my first S-100 CPU board -- around 1977 or so -- was/is a "Base 2" Z80.)
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Jonam
12/17/2009 6:04 AM EST
I learnt a lot about computers and electronics on a Z80 based Microbee (Australian PC) in the mid 1980's while studying for my EE degree. I hope Zilog survive.
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K1200LT Rider
12/17/2009 8:46 AM EST
The Z80 started my computer-related learning inside a TRS-80 Model 1 with a cassette for program storage. I still have that thing in a box in the attic. Someday I'll get it out to see if it will still run.
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Walter Greene
12/17/2009 8:51 AM EST
Alas poor Z800, I wish I'd known you.
Back in the day when the Z80 was strong the Z800 was promised. Those of us who wished to use this golden part waited with bated breath for samples...and waited...and waited...and waited. We then moved of to other devices that were actually available. I suspect that the early announcement, then failure to deliver the Z800 was the companies eventual undoing. I've worked for strong companies that have overpromised and are no more. PictureTel for one. The mistake of pre-announcing product (better, cheaper) and failing to deliver has caused dramatic collapses. et tu Zilog
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Chida
12/17/2009 1:57 PM EST
I have worked at Zilog earlier and have worked on 8 bit microcontrollers. This is when I understood the beauty of orthogonal architecture. I hope this merger brings a new change for ZiLOG. Merger or bankruptcy, long live the King...
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studleylee
12/17/2009 3:32 PM EST
I started HW/SW with Steve Ciarcia's Z80 HW book and the Sybex's "Programming the Z80" asm book. Over the years I've used many venders parts, but the Z8encore and variants have always proven to have a good dev( asm, C )practically free environment and good hardware without tons of errata. I hope they stay around.
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svik
12/20/2009 12:03 PM EST
I did one little Z80 project. Have used the 64180 once. But Zilog is not even on the MAP. I have not heard of a development kit or an add for a nice integrated CPU with a cheap development kit???
Right now I am using C166 and Microchip ICs. Recent CPUs were Coldfire, powerPC, ARM, 80251, etc Where is Z80???
The Z80 may have an nice 'orthogonal' instruction set, sure!, but what do I care I program in C. What matters more is the quality of the C compiler.
And how can they not make money??? Desiging the IC is not that difficult. Outsource the production and market the chips. I suspect they live in expensive $$$ area of California with expensive tastes.
I just looked at the ZILOG web site to see if I could pick a nice IC with flash and loader and C to go. All I got was flashy pictures. Where is the CPU selection .............
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davi_viotto
12/20/2009 3:15 PM EST
It was a great era that was born in 8080 and split into two teams, the ZILOG good software with the z80 and INTEL good hardware with the 8085. I studied and worked with these beasts!
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Monte_Dalrymple
12/21/2009 11:12 AM EST
The Z800 and the Z280 are the same design. The Z800 was done in NMOS while the industry was in the process of switching to CMOS. So management paid an outside firm to convert the finished design to CMOS. Saying that it would cost too much to convert it to Zilog's CAD system is a bit disingenuous. Management made a concious decision to move it from the internal CAD system to that used by the outside design firm.
The Z800/Z280 CPU design used a "textbook" microcode implementation (i.e. grossly inefficient). Memory reads and writes were done with subroutine calls in the microcode, incurring a one clock penalty on entry to push the retrun address and a one clock penalty on return to pop the return address. There was another one clock penalty at the end of every instruction to avoid a collision on the internal bus between the opcode being fetched and the operand being written. When I took over responsibility for the CPU design (the original designer left the company before tapeout) I told management about these issues and asked for three weeks to fix them. Needless to say the answer was "no". When I asked again before the CMOS conversion was started the answer was again "no". In both cases the rationale was "we'll lose too many customers with the delay". Of course the lack of performance lost even more customers.
The Z80 still lives (in mutated form) in the Rabbit microprocessors. And a Z180 clone will head to Jupiter (inside a rad-hard FPGA) on the Juno mission in about a year. So yes, the architecture still has life in it.
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JHDodd
12/22/2009 5:19 PM EST
Another of their memorable creations was the 8530 Serial Communications Controller which is also still in production.
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