8080 Cpu, Is this totally useless?!
rwgast_logicdesign
Posts: 1,464
So I had a radio shack/archer 8080 fall from the sky still in the package. I cant find many hobby projects based on these, anyone know of any 8080 projects besides mk1/2 and imasi?
Comments
Altair 8800 also, the FIRST one. If you don't want it, i'll buy or trade.
-Phil
This caused me to fondly(?) remember all the soldering and pieces parts that went into building those old s-100 beasties. It was a monumental accomplishment when you finished and blinked THOSE LEDs!!!! I like the future!!
Ive seen alot hobby breadboard computers done with z80 and 6502, Blondie hacks has an excellent guid to doing a 6502 with video and everything, I was hoping the 8080 would have the same sort of scene going on. From what Ive read the thing requires support chips as phil mentioned and all the home brew computers are very complicated looking with an s100 bus, seems like a lot of time a dedication would have to go in to a project like this, to bad.. I just have no intrest in doing an s100 bus computer. Now if a simple SBC was possible with sourcable chips that would be another thing
FF
Phils right. The 8080 was. PITA chip requiring 2phase clocks from an 8024? Clock generator chip. Much better if you want that family to go with the 8085. Personally I like the Z80 because so many things can be derived. Using the early 64 and 256 k * 1dynsmic rams were simple to design with. Even when you had to cut holes in the address space for (e(p)rom while still keeping the dynamic ram properly refreshed. Used that for long time.
Seriously, the 8080 is a part of history.
While not the first integrated 8-bit micro, the Intel 8080 was the first to be widely used.
I actually have a micro built with the first, but venerable, really slow forerunner the 8008.
Don't throw it away, frame it and put it on display.
Oh, and fast forward into the 21st century and make a Prop which will run circles
around the 8080, and much simpler to build.
Duane J
Biggest problem I see is the need for a few different power supply voltages including -5v if I remebember correctly. Not insurmountable.
But perhaps the best suggestion is to frame it and hang it on the wall.
The reason I want to build an SBC is to learn computer architecture in way most people havent since the 1970s when building your computer was the norm. I feel this level of knowlege would tend to make one a much better programmer and it would be an ideal way to have a platform to learn assembly language on from the ground up, none of those OS provided interrupts to lean on!
My issue with this is I feel the x86 and arm architectures are here to stay so if your going to take on a project this deep build around a platform in which the knowlege you gain will be applicable today. This is the problem I have with all the 6502/mc68000 builds, granted you learn so much but the skills arent directly applicable to your desktop PC, you will still have to learn a newer architecture. The problem is as a hobbyist its impossible to use any modern x86/ARM CPUS to build a home brew around, in the x86 world this is do to complication and chip package, no hobbyist is gonna work with a 5000 pin bga chip lol. With ARM i think the problem is partially packaging, im pretty sure that you can get an ARM9/11 core CPU in SMT still but the issue here is IP and licensing if your not qualcomm your not getting any arm11 chip and full documentation in a small quantity! So if you want a hobby friendly package you would have to go waayyy back to get it
So if you really want to design a computer as a hobbyist it seems the only choice you have for cpus are old 40 pin dip packages. Also im sure these are the only CPUs that arent so advanced only a team of engineers could figure out how to design for them! I have always been curious how hard it would be to break out an old 386/486 chip and build around, this would be my #1 option but im sure it would be very complex! So now what chips meat these requirements
There in package that is accessible to some one with a set of common tools at home
The knowledge gained from building and bootstrapping the system can directly translate to modern computers/gadgets
They CPU itself is understandable to a single meer mortal just getting started with home brew
In my mind this left the 8080 or the z80 running intel compatible instructions only.. Im saddend to learn that the z80 was a huge clean up over the 8080 and it is probably earier for the home hacker to ditch the 8080 for a zilog chip
From what you guys are saying, and what ive read it seems like i need to design a power supply capable of -12 +12 volts, get my hands on old perpherial chips and the chip to multiplex the 8080, and probably make some crazy altair s100 design
I have no problem using a propeller like the Apple Clone, but could a propeller be used to replace these arcane chips the 8080 required without alot of hard work? This is distracting from the acuall computer.
Im not sure if theres newer z80s like the 20mhz 6502s, but if there were this would probably be the best bet? Especially if you intend to try to mix more modern features and chips into the design then what was available back then? Im not after retro.... Im after doing everything that needs to be done using the best modern technology a hobbyist can buy, but still sticking to the traditional way of doing things for the most part. I mean using a prop for HID is kind of cheating but im mostly ok with that, using a prop to creatively replace some chips with a much better system im all for. I guess what im saying is as modern as possible is definately a plus and any new technology is good as long as it doesnt take away from any of the educational value that goes into desiging a computer.
http://www.ebay.com/sch/i.html?_nkw=8088+processor&_sacat=0&_odkw=8088&_osacat=0
A two phase clock shouldn't be too hard to make. Just need a 2x faster clock source, an inverter, and two T-flip-flops. (or some code in the support Propeller) For me, weather it's worth coding the support chips in a Prop would hinge on how well documented the support chips are, and how much they have to do.
Lawson
I would urge you to start with the Z80 and consider using the propeller as the terminal interface and I/O chip. The Z80, 2 32KB ram chips or 1 128KB ram chip and a Propeller with the eeprom and crystal would be all you need for an excellent learning system. My second computer was a Z80 with 64K of ram and 2 5.25” floppy drives. I did all my quotes, contracts, invoices, and accounting for my business on that system.
Z80:
16 bit non multiplexed address bus (for 64K bytes of memory), 8 bit data bus, 256 I/O addresses.
A very simple system could be built with as few as 3 chips, although 4-5 is more usable.
8088
20 bit multiplexed address/8 bit data bus (for 1MB ram), 64K I/O adresses. A very simple system could be built with 4 chips, but 5-6 would be more usable.
V20
An enhanced version of the 8088 from NEC. All of the 8088 instructions plus some additional ones and a very similar pinout to the 8088 (may be pin equivalent but I am not sure). Same number of chips as 8088 for minimal/usable system.
This was a concept I was introduced to in 1982 at a conference on using this device family for a micro-coded processor emulator. I was invited to tag along with two of the Data Systems instructors I knew from Mare Island Naval Station in Valejo, Ca. They were assigned to teach the third phase of the training which was built around the AN/UYK-20, a microcoded emulation of an older Sperry computer used in various shipboard computer systems. Of course the part of the course relating to the processor emulator part of the unit was affectionately known as the personnel eliminator. Fun times,
Frank
Here's ALE's 68k board with a Prop, he also uses a couple CPLDs, which are something most electronic hobbyists should acquaint themselves with.
Link:
http://propeller.wikispaces.com/pPropQL
Here's a Z-80 based board:
http://www.cosam.org/projects/z80/
And here's one that uses a 20Mhz Z80 and a FPGA
http://www.retroleum.co.uk/v6z80p/
Start with taking a look at this blog btw: http://quinndunki.com/blondihacks/?p=680 It doesn't take much to get a 65C02 going!
-Tor
I was thinking of suggesting something along that line using the '181 ALU chips. I decided that was not a good idea. Quite a bit of work involved using the '181 or the AM2900 chips.
@rod1963
Nice projects. Thanks for posting the links.
@Tor
Building a computer with the 6502, 680x, Z80, or any of the second generation 8 bit chips with simplified interfaces and single voltage supplies is not that difficult. A working system could be built with very few chips if you don't need a lot of I/O.
There is even a completed project by Dennis Ferron that uses a 6502 and propeller to build a laptop computer. I don't have a link to the thread but perhaps someone will know of it.
I would really like to design it as modern as possible though maybe something like 8 to 16mb of dram on 20mhz z80. Will getting that much ram to work with a z80 pose any problems at all?
For anyone like kwinn whose done this kind of a project around a z80 maybe you have some recommendations of basic chips I should use for the project since youve already done this and know what works well and what doesnt,
You're giving me more credit than I have earned here. The largest Z80 system I have built was 256KB, and that was static ram and eprom. As rusty as I am with Z80 assembler and hardware I would not want to tackle the software for refreshing DRAM. Also, the Z80 will only directly address 64KB so you would need paging hardware and software to make use of any more than that.
Unless you go to a Z80 derivative that can address more memory and refresh DRAM I would recommend you stick with a Z80, 32-128K SRAM, use a propeller to boot the Z80, act as the serial terminal, and interface to an SD card for mass storage. You will learn just as much from that system as you will from a much larger one, and you will have source code for the OS and other programs to study. In addition to that you will have this forum for when you need help. Lots of Z80/CPM knowledge available here. I might even have source code for a small monitor program somewhere.
Program in assembler withou OS - free
Flexibility offered - Priceless.
Cambridge University is building an OS course (available online) around it.
It's on my list of projects.
I think it would be fun.
If you wanted to do graphics old school style you can buy off Ebay one of the older graphics controller chips.
I agree, that would not be a good first step. The 8088 is a possibility and it does address more memory (1MB), but it is more complicated to work with from both a hardware and software perspective. I really would suggest using the Z80 in as simple a setup as possible to start with. The basics you learn from that will prepare you to tackle something like the PI.
That said, the actual hardware of the 1970's was a pain to work with. I'd much rather do an 8080 Prop cog than work with an actual 8080 chip, just as I'd much rather work with 80's and later SRAM than the fickle 4116 DRAM, which required multiple power supplies and all kinds of weird timing. Fun story -- the 4116's used in my 8080 computer had 4 power supplies, and the spec sheets said it was ABSOUTELY NECESSARY that the +5V come up last. The fellows who designed my computer accomplished this by leaving the other supplies on all the time and just switching the +5 with the power switch.
So, some of them members of our little user group decided they liked the convenience of turning on their whole system with a power strip, and this kind of foiled the intentions of the power supply designers. It still usually worked, but every once in awhile the +5V would win the power supply startup race. And what, you might be wondering, would happen then? All eight DRAM chips would EXPLODE like little DIP firecrackers. In the day replacements cost ove $100, and of course they were soldered in.
The 8080 itself also required multiple power supplies, support chips to generate the polyphase clock and multiplex the address bus, and several other functions I only vaguely remember. There were several Intel support chips which had no useful function at all except making 8080 design less nightmarish. It might be an interesting exercise in retro mad skillz to try to make an 8080 do anything at all, but it would be pretty hardcore and unlikely to be useful for much more than bragging rights.
Yes, I have a soft spot for the 8080 as well, but not soft enough to consider using it to build a computer. My first computer was an 8080 based S100 system that I assembled from bare boards I purchased at a computer show in Atlantic City. I learned an awful lot about computers, electronics, and 8080 assembly language programming from that.