DIY old school computer 8080 based or z80 - Page 1
Forum section: electronics / general

author: Napalm2002
author_rank: Regular Contributor
timestamp: May 15, 2014, 12:29:41 am
content: Suddenly i have an interest in building an old computer. The Altair 8080 seems very cool and I would like to build one. Any kits available? I have no clue where to look?

author: centon1
author_rank: Unknown
timestamp: May 15, 2014, 12:55:04 am
content: Site appears dated but it would be worth an email to them.http://www.altairkit.com/I preferred the KIM-1 6502 myself which also have updated 'clone' kits out there.http://oldcomputers.net/kim1.html

author: Napalm2002
author_rank: Regular Contributor
timestamp: May 15, 2014, 01:20:23 am
content: Cool. I think the Altair one is very cool but I was looking for a much cheaper DIY kit. Any ideas anyone?

author: westfw
author_rank: Super Contributor
timestamp: May 15, 2014, 08:03:01 am
content: There's also the 8085, which is a modernized (~1978) version of the 8080, without as many enhancements as a Z80. You can apparently still buy them.Are you interested in "old school" hardware, or software? There are really modern versions of Z80s, with on-chip Flash and peripherals, that you could probably put CP/M on and play. But if you're looking for a front panel with lots of lights and switches, you'll need to remember that those components have not seen as much decline in price as semiconductors, so "really cheap DIY" is going to be difficult to find. Mechanical components, huge PCBs...

author: amyk
author_rank: Super Contributor
timestamp: May 15, 2014, 01:04:08 pm
content: If you wantreallyold school, try a 8008 or even 4004. Not cheap though.

author: miguelvp
author_rank: Super Contributor
timestamp: May 15, 2014, 04:35:35 pm
content: Quote from: mojo-chan on May 15, 2014, 03:33:36 pmOS-9 is awesome for an old OS, but I didn't get to play with it until the 68000, a friend of mine had one of those dragon or bbc something, that they were designed to be compatible (or cloned) with other OS-9 systems.Memory addressable ports (Edit: should actually say I/O) for the win!

author: Dave Turner
author_rank: Frequent Contributor
timestamp: May 15, 2014, 05:34:45 pm
content: The first computer I built, back in 1976, was based on a Z80. A very useful feature is that the clock can be manual stepped which is excellent for testing. In the absence of an oscilloscope and/or logic analyzer it enabled a handful of buffered leds to diagnose most issues.Of course the original Z80 only had a 1Meg clock and TTL logic so the circuits were relatively forgiving as opposed to working at Gigs.I'd suggest going with a Z80.

author: miguelvp
author_rank: Super Contributor
timestamp: May 15, 2014, 05:54:11 pm
content: Quote from: Dave Turner on May 15, 2014, 05:34:45 pmMy first system was also z80 based (zx81) fried the cpu by connecting TTL logic on the expansion port with sawed in connectors, because the ones that were the exact connector was way too expensive. One day a stray cable touched the connector and the CPU bought the farm. Ordered a CPU and back then it took 4 to 6 weeks to get it, but there was a book on the store about Z80 assembly. The samples were intended to be run with a microprofessor (which I didn't have) so I did all the samples by hand while waiting for my replacement CPU to arrive.It gave me a good understanding of the chip to say the least.2nd one was the zx spectrum (which I got after the zx81 by saving my allowance for many many weeks and doing lots of chores).First thing I did when I got my hands on a PC is to make a macro assembler (well the only macros were well known spectrum memory addresses) but it would convert mnemonic to a binary file.Made a tape reader that will run on the original IBM PC as well by using the din connector on the back.Also did an emulator for the PC, got it to boot but never put the effort on emulating the keyboard properly.Maybe I'll dig out that code and post it (horribly written of course and probably totally undocumented) if anyone wants to take a peek of some 25 year old code written by a very inexperience coder before going to college.

author: SeanB
author_rank: Super Contributor
timestamp: May 15, 2014, 06:35:29 pm
content: Z80 also has the very important advantage over the 8080 in not needing a very picky clock driver to make it happy. I have a load of old Z80/8080 peripheral chips somewhere.

author: westfw
author_rank: Super Contributor
timestamp: May 15, 2014, 08:40:44 pm
content: Recently I've been wondering if I can use something like a PIC to control the clock signals of one of those "classic" CPUs to get better debugging and fewer chips. (like an 8051. 12 clocks per instruction, eh? Ok, here I go. un-reset, one clock, two clock... looks like an instruction fetch; ok I'm synchronized. 6 clocks at 16MHz should get me to the memory fetch - is it xram? Ok, I can stretch that cycle and ... another clock ... put the data from MY RAM on the 8051 bus, and ... a couple more clocks. Oh look! An access to the theoretical external 8255, which I happen to be simulating... Etc. (inspired by this:http://hackaday.com/2013/02/08/another-take-on-the-6502-computer/)There are a lot of "retro" computer projects mentioned on HackADay. Mostly 6502 and Z80, but also 6809, 68000, etc.

author: dajt
author_rank: Contributor
timestamp: May 15, 2014, 10:44:35 pm
content: I've run a Z80 using a clock signal from an AVR. Varying the clock speed was fine but I was doing it holding RESET active rather than doing it while the Z80 was awake.

author: MarkL
author_rank: Unknown
timestamp: May 16, 2014, 11:22:15 pm
content: Kits??If you really want to experience the DIY 8080A/Z80 days, you could try your hand at wire wrapping a system together. Although not nearly as common anymore, you can still get wire wrap DIP sockets, wrapping tools, and wire. These are simple chip sets and it's not nearly as hard as you might think.A couple of good books are "The 8080A Bugbook" ISDN 0-672-21447-4, and "The Z80 Microcomputer Handbook" ISDN 0-672-21500-4. (Both are available at outrageous new-condition collector prices, or used for a few bucks.)And for extra fun you can get CP/M running on it. The original CP/M is available athttp://www.cpm.z80.de, along with the source code and various emulators, compilers, etc.

author: dajt
author_rank: Contributor
timestamp: May 17, 2014, 02:59:31 am
content: I wish I was wire wrapping rather than soldering to protoboards but the cost seems prohibitive. I haven't seen anything related to wire wrapping which is cheap enough to be used to "have a go".Re books,www.archive.orghas a great selection of legally downloadable stuff, alsowww.z80.info, andwww.6502.org.

author: miguelvp
author_rank: Super Contributor
timestamp: May 17, 2014, 04:14:46 am
content: Let's not forgethttp://www.visual6502.org/With their Visual Transistor-level Simulation that you can see the processor while running code.And they do have one for the 6800 as well as source for both (in javascript).

author: Napalm2002
author_rank: Regular Contributor
timestamp: May 17, 2014, 06:32:31 am
content: Thanks to All who posted. Now I just have go figure out what I want to do...

author: BloodyCactus
author_rank: Frequent Contributor
timestamp: May 18, 2014, 02:24:28 am
content: check out Quinns 'Veronica'.http://quinndunki.com/blondihacks/?page_id=1761some really cool stuff there!

author: eurofox
author_rank: Unknown
timestamp: May 18, 2014, 12:40:27 pm
content: I wrote a lot of code for 8080/8085, Z80, 6502 all in assemblyPID, Floating point, I/0, mutitasking OS, communication protocols, 8086 with CP/Mbut funny time, no internet for help, very basic literatureeurofox

author: Napalm2002
author_rank: Regular Contributor
timestamp: May 19, 2014, 03:41:05 am
content: Bloody cactus Veronica is awesome. Want to build it!