Any other builders ?

[ghost]

I have a collection of older machines (ranging from 8 bit home computers to some 32 bit Unix workstations from Sun and SGI) but I'm more interested in building a small 8 bit machine from scratch. That's something I have wanted to do since I was a teenager but never seemed to have the resources available.

Now that I do have access to everything I need I've started on the project (I set up a blog at My '09 (http://my6809.blogspot.com/) to document the process). I'm basing my system around a 6809 CPU (hence the title of the blog) simply because I have a handful of them in my parts collection.

I'm interested to see what the combination of an older CPU with some newer periphials can do (I'm looking at SD cards for storage, VGA for display, PS/2 for keyboard/mouse and ultimately and ethernet interface). I'm planning to use the newer AVR and PIC microcontrollers to do a lot of the IO busywork so the slower clock speed of the CPU won't have as much of an impact on things.

I'd be interested to know if anyone on this forum has done or is working on something similar? I've seen a few older posts on the topic but nothing that recent.

[Thrashbarg]

Yes, I've done this sort of stuff before.

http://kaput.homeunix.org has got details for my main 8080 project and a side 8088 project. I've got a 68E09 in my parts draw but I haven't found time to make it into something. I probably will some day, but not at the moment.

The 'newest' peripheral I've attached to the 8080 computer is a YM2151 sound synthesizer which has had its date code machined off. I would imagine it's from the late 80's.

Personally I don't really like to use newer microcontrollers in my projects, unless they're stand alone. I consider it cheating ;) . If you want to, go for it. It will really show off what the older CPU's are capable of with a bit of a leg up.

What do you intend to run as an OS, if any? There's UniFLEX for the 6809 which would make for a very interesting project. http://www.rtmx.com/UniFLEX/index.html

[ghost]

I came across your project in previous threads - it's very impressive. I'm putting my prototype on breadboards rather than wirewrapping or prototype boards to start with. I have heard of some problems with high frequency circuits on those though, I've never experienced it with my PIC or ATMEL projects but they tend not to use a lot of the boards surface area. Have you heard anything about this?

As for operating systems - I was considering NitrOS9 (http://sourceforge.net/projects/nitros9/) which is similar to uniFLEX. If the uniFLEX source is included in the page you linked to I'll have a look at that as well - thanks for the link. Operating system work is my 'day job' so I was also considering writing a simple kernel from scratch. This is one of the main reasons I want an '09 based board - to play around with this sort of thing :)

What OS are you using on your systems? I think I saw CP/M mentioned - was it difficult to port to your specific systems ?

As for using microcontrollers in the design - I agree it is cheating a bit (at the very least not in the spirit of 'vintage' design) but I'm more after functionality. I have a few GAL's (and a programmer that supports them) so I was planning to use those to replace the discrete logic components as well, especially for the paged MMU.

Best of luck with your project :) I'm not sure I'll be at the same level of functionality in a years time but here's hoping :)

BTW: I'm from AU as well, but further north in QLD.

[Thrashbarg]

What OS are you using on your systems? I think I saw CP/M mentioned - was it difficult to port to your specific systems ?

Not really. Gary Kildall designed it so it would be easily portable, where the target machine could use all of the existing code without having to assemble it, and just make a custom BIOS.

What I did however was compile the original source with the correct memory targets, rather than running the binary through the relocator. I didn't have a CP/M system to start with to do the relocation on. I could probably have used an emulator but it was quicker to go straight from source.

I probably should finish reimplementing the floppy disk controller so I can use MFM disks and an IDE hard drive. I've been busy with other projects though.

[davidB]

Hi everyone, just joined this forum.

I built a Z80 computer many years ago, partly wire-wrap and partly home-etched boards, when I was fresh out of college, had sent out a pile of resumes and was sitting around waiting for a job. I used a freeware compiler to write the OS (if you can call something so simple an operating system) and burned it into an EPROM with my own homemade EPROM burner. The high point of that project was that it had a speech chip, so when I booted it, it would say a greeting, then would speak messages and error codes. For me, half the fun was writing the OS to read the EPROM, access the RAM, accept input and respond, etc. It was so great to have it successfully boot and run, even if it didn't do much.

My hobby at the moment is using microcontrollers to access data storage devices. So far I've succeeded in reading and writing IDE hard disks and dynamic RAM, and have read from MMC and SD cards and 3.5 inch floppies. Currently I'm trying to read files from a 5.25 inch floppy, using my 3.5 inch controller codes. I can start its motor and step its head but aren't getting any sync from the data pulses, and I'm wondering if 5.25's have different data pulse spacings...

David

[ScrappyLaptop]

You might want to also check out the yahoo groups 'PARTS' (Portland Area Robotics) and 'ROBOTICS'. Some of the postings mention references bit-banging IDE interfaces with PICs...

[MikeS]

Hi everyone, just joined this forum.
Snip>
Currently I'm trying to read files from a 5.25 inch floppy, using my 3.5 inch controller codes. I can start its motor and step its head but aren't getting any sync from the data pulses, and I'm wondering if 5.25's have different data pulse spacings...

David

Fer sure; different data rates and RPM, depending on *which* 3.5 and *which* 5.25...

mike

[lynchaj]

Hi,
I started out as a "builder" and built a Z80 computer from scratch. It was a lot of fun. The computer ran CP/M, had an IDE interface, serial port, parallel ports, 512K RAM and 32K EEPROM. It certainly was a learning experience and a good time too.

My plan is to return to that machine to make the video card I planned on but since then I caught the "repair" fever and have been fixing broken vintage computers since. There is something about finding an old broken pile of parts that just makes me want to fix it. Sort of like a puzzle or something.

Definitely building computers from scratch is a lot of fun. Eventually I would like to build an S-100 machine from scratch too. I have been collecting plans and parts. Now all I need is a spot in the workshop not filled in with old NorthStars or Vector Graphic stuff.

Thanks!

Andrew Lynch