Opinion: 8085

[rivalejo]

i've read, and heard that the Intel 8085 microprocessor is used extensively for educational purposes, why do you think that is?

 

[kchriste]

It's old so there are lots of books on it and instructors well versed in it. It is the precursor to the Z80 and then the 8086-->Pentium. It is long obsolete, but the basic principles of CPU's haven't changed that much since it's inception.

 

[Nigel Goodwin]

It is the precursor to the Z80

Was it?, certainly the 8080 was, but didn't the 8085 come later than the Z80?.

Basically it's still used by educational departments that haven't updated their courses or equipment for 30 years!

As suggested though, programming is programing, no matter what the device.

 

[colin mac]

I learned about the 6502 last year for the same reasons. There's really no excuse for still teaching about them IMO, when I think back. Teaching uC's would have been more beneficial since people still use them and the same principles apply.

 

[ronsimpson]

Forgive my fading memory!

I remember the 8080 to be a great advance forward. (made by Intel) Hardware wise it was very simple requiring much less parts.

The 8080 required a complex clock oscillator and many support chips. The board required three supply voltages. By today’s it was very complex.

The 8085 from Intel had an on-chip clock oscillator. Ran from a single 5 volts. Hardware wise it was great! Software it had no advantage. We actually did imbedded computers with it. Many schools used it because it looked like an 8080 from a software point of view but came on a small cheep board that schools could afford.

The Z80 from Zilog had a software huge advantage. It could act like an 8080 but it had twice the registers. Many more instructions. New addressing modes. Handled interrupts much better. Faster.

From there things went two different ways. One track was the 8bit to 16bit to 32bit to 64 bit run that created out PCs of today. The other direction made computers smaller. The external ROM memory and external RAM memory and external parallel and external serial ICs were all combined into one part. There was a time where adding a serial port to a computer required an IC the size of my thumb. Today I am working on a computer and switching power supply that together are the size of my fingernail. It is 1MIP in speed, much faster than my first 8080.

 

[kchriste]

Was it?, certainly the 8080 was, but didn't the 8085 come later than the Z80?.

I believe you are correct here. According to Wiki, the Z80 came out in July 1976 and the 8085 in 1977. The z80 has a much more advanced instruction set which probably lead my fading memory astray.

 

[dknguyen]

We use the Motorola 68000 at my university. A guy (a young guy mind you) at work told me that when he was in university they used some processor that had zero periphreals. So if you wanted a UART you had to wire one up. If you wanted anything other than just pure logic you had to wire it up to the processor. Ouch.

 

[Nigel Goodwin]

We use the Motorola 68000 at my university. A guy (a young guy mind you) at work told me that when he was in university they used some processor that had zero periphreals. So if you wanted a UART you had to wire one up. If you wanted anything other than just pure logic you had to wire it up to the processor. Ouch.

The 68000 was (and is) like that, pretty well all micro-processors are?, a micro-controller is a micro-processor plus support peripherals inside, which is what makes them so useful.

 

[simrantogether]

Well...

Hi,

A feeling is there as why 8085 is preferred in educational institutions because it was made popular knowingly by intel ( i feel )... **broken link removed**... it suffered tough competition from Zilog Z80.

So...

Regards,

Simran..

 

[3v0]

I learned about the 6502 last year for the same reasons. There's really no excuse for still teaching about them IMO, when I think back. Teaching uC's would have been more beneficial since people still use them and the same principles apply.

The old microprocessors have external address and data buses. This allows you to hang a logic analyzer on the system and do a trace. You can not do that with a modern uC which does not provide access to address and data buses.

This is what I was told when I was in school.

It matters little that we are teaching you to use an old processor. The fundamentals still apply. Had you learned on an modern processor the changes of you getting a job using that processor is small.​

For the most part they were right. Most schools can not afford to buy the equipment needed to support development on new hardware. I am talking about processor emulators which have advantages over simple ICDs which provide only run control.

Given the quality and price of tools like the PICkit2 (or better yet Junebug) I think that it would make a good platform for an introductory class. Maybe teach the processor emulator and logic analyzer related stuff in a 2nd class. Weed out the chaf prior to getting to the expensive equipment.

 

[Analog]

It's old so there are lots of books on it and instructors well versed in it. It is the precursor to the Z80 and then the 8086-->Pentium. It is long obsolete, but the basic principles of CPU's haven't changed that much since it's inception.

Zilog's Z80 was a clone of the 8080 that Faggin designed after leaving Intel and forming Zilog.

The 8085 came later. It was superior to the 8080 because it was simpler to use with only a 5V supply, and basic oscillator.

I have been teaching microprocessor courses for over 10 years, and the use of the 8085 was abandoned back in the 90s. Why? Not because its a good micro to learn about - it is. But the software tools are primitive and the evaluation boards are nonexistent. We have moved into the 68HC12 for our introductory micro class, and the PIC18F4520 for our advanced class. This is in large part due to the software tools and boards available. These newer processors all have emulators and C support that is cumbersome for the venerable 8085.

 

[Dean Huster]

Most every single-chip processor has had its inclusion into a training system of some sort. Heathkit used the 6800 for years and years. The 6502, Z80, 8085, 1802 and other 8-bit processors all had their educational platforms, some as structured training systems such as Heathkit's, others as inexpensive experimenter's kits like the 6502. The 8080 got its big jump-start with the MITS Altair and IMSAI computers while the 6800 was the core of the Southwest Technical Products machines. Most of the original processors required more supply voltages and support chips and these were the two areas that were taken care of with the next generation of µPs. I could never imagine learning about basic microprocessors using an 8088 or anything more modern. That'd swear you off them forever!

As Nigel observes, programming is programming. You're usually learning basic microcode instructions and interfacing that changes from processor to processor, so no one processor is going to be of any advantage over another. Just like learning digital logic -- you can do it using "ancient" TTL just as well as more modern families.

Dean

 

[3v0]

I do not think Dean intended to say microcode in the previous post.

 

[Dean Huster]

Why didn't I? Machine language. Microcode.

At Tektronix, they always referred to the processor's instructions as microcode as differentiated from BASIC programming language.

Dean

 

[aussiepoof]

Why didn't I? Machine language. Microcode.

At Tektronix, they always referred to the processor's instructions as microcode as differentiated from BASIC programming language.

Dean

More correctly Machine Language is the binary instruction set interpreted INTO a series of Micocode instructions that actually move bits/bytes inside the processor to execute the instruction. The z80 took 4 (or more) clocks to execute one machine language instruction because it required 4 (or more) microcode instructions.

Of course there are processors without microcode... so called asynchronous designs but my fading memory fails to recall if any commercial CPU used this method.

P.

 

[3v0]

Aussiepoof is correct. I find it interesting that the people at Tektronix misused the term given that they build logic analyzers.