An Introduction

[Steve Garcia]

Hello everyone,

I would like to introduce myself. My name is Steve Garcia and I've been working on my own homebrew computer project for the last several years. I haven't posted anything yet because I was trying to make everything perfect. But I've come to the realization that there is no "perfect", so I'm stepping up now.

For the last three years, I've been working (playing?) on what I call the Dyno Computer. It is a Z180 computer based on the Micro-ATX form factor and initially designed to run Wayne Warthen's RomWBW. It has an six-slot expansion bus called the Dyno•Bus.

Fort last month or so I've been preparing a website to display my project; but like everything else, it's not perfect. There is still a lot to technical information I need to include. But I wouldn't mind a little feedback in the meantime. It is located at:

https://homebrew.computer

Again, thank you all for the exciting projects you all create all of the time.

Steve

[Mark T]

Looks really good, thats a lot of boards you’ve designed already.

Does it fit a micro ATX case? It would be interesting to see pictures of a cased system.

Mark

[Sergey Kiselev]

Hi Steve!

Welcome to the group!

I am glad that my Zeta SBC project was an inspiration (and a learning moment) for you.

The Dyno motherboard looks great. I like that you choose to use card edge connectors - they are easy to work with.

If I had a choice, I'd probably make it at least somewhat 8-bit ISA compatible, but that's only because you already use a form factor which is very similar to a PC. Although that would require some additional logic to convert Zilog control signals - /RD, /WR, IO/M, /M1, to 8088-compatible /MEMR, /MEMW, /IOR, /IOW, and probably insert some wait states to accommodate slower peripherals

Thanks,

Sergey

P.S. Frist when I looked at your name, the name of Steve Ciarcia came to my mind (same first name, very similar last name). He wrote several books/articles about computer design back in 80's.  For example this one: http://www.pestingers.net/pdfs/other-computers/build-your-own-z80.pdf is a good read if you're into designing your own computers.

[Tom Storey]

Crikey, thats an effort and a half to create all of that.

I do like the logo. :-)

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[Wayne Warthen]

Hi Steve,

Nice to see this project go "public".  Looks very nice.

-Wayne

On Wednesday, February 17, 2021 at 9:13:03 AM UTC-8 webmaster.hom...@gmail.com wrote:

[Rob Gray]

Ha ha, when I saw your name I thought it was a joke :) (See Sergey's comment about Steve Ciarcia)

This is a VERY impressive project. Well done, a huge amount of work and all the boards look good. I'll be spending some time looking through them all. 

Rob

[Colin MacArthur]

GREAT Project...

I love the Micro ATX size as you can find old ATX cases & power supplies in the junk bin at almost any computer shop...

I always like to see E-Recycling as opposed to filling up the land-fill.  

Just as a comment, it looks like you are using MC14495 chips for your "Bus Monitor"  and "Debugger".

Lately I have found them  very scarce and very expensive these days.

You may want to look at:

https://www.instructables.com/Dual-BCD-to-Hex-7-Segment-Driver/

or

https://hackaday.io/project/163274-4-bit-full-hex-decoder

or

https://github.com/linker3000/GALBinaryTo7Seg

I have been using the GALs for HEX 7 Segment displays ever since I ran out of HTIL-311A displays.

They work GREAT...

There was also someone playing with a 14 pin PIC16F as an almost pin for pin replacement, but I have not tried it...

THX

CM

[Steve Garcia]

Hello everyone,

Much thanks for the great responses I've received. I'm sorry for the delayed reply, but work's been crazy.

Mark T asked about motherboard mounted in an Micro ATX cases. I have a couple of pictures, one of an older prototype that I used to confirm that the board would align to the mounting screws and slot openings:

 and another with my current prototype with cards installed:

I usually don't have the prototype in the case because it's awkward to work on. Most of the expansion cards are low-profile because I was planning on using a low-profile case. One of the open issues I have with the expansion cards is securing proper mounting brackets. I chose to use the PCI orientation for the expansion cards (with the components on the left side) rather than the old IBM PC orientation (with the components on the right side) because I wanted to have available of that little strip of circuit board real estate (near the left edge) for components (otherwise the slot socket is right against the edge) and because I could only find low-profile brackets for the PCI orientation.

I am aware of Steve Ciarcia (from old Byte Magazine articles) and was introduced to his book "Build Your Own Z80 Computer" by Dr. Scott Baker's blog when he mentioned it as a reference source for his Single Stepper for RC2014 project. I'm just a beginner with electronics so most of Mr. Ciarcia's work goes over my head; but I'm trying to understand. But until you all mentioned it, I never realized my name is so close to Mr. Ciarcia's name's spelling.

Sergey Kiselev had mention supporting the 8-bit ISA bus. I had actually thought of that, particularly in order to make use of old video cards like CGA or MDA (I have an old Amdek monochrome monitor in my garage somewhere), but I was a little intimidated about the prospect, thus making the Dyno•Bus a simple extension of the Z180's data/address/controls lines would be enough of a challenge to start with.

Colin MacArthur, actually I'm using DM9368 chips to drive the 7-segment displays on the Dyno•Bus Bus Monitor. This expansion card was inspired by Dr. Baker's RC2014 TIL311 Front Panel Board. Although the DM9368 are expensive and scarce, the TIL311 Dr. Baker used were more expensive; so I thought that DM9398 was a good compromise. But I see your point about using GALs. I use them quite extensively for glue logic. Thanks for the references.

By the way, I have purchased some MC14495D chips as well as some TI DIS1417, but I haven't used them for anything yet. I've played with AVR (Arduino and such), but I haven't done anything with PIC yet.

I have though about making the files available for others, but that nagging need for perfection gets in the way. My particular concern is that I need the design for the Dyno•Bus to be firmly defined. Once it is released to the public, making changes would be difficult. There are still a few issues I haven't decided yet. I'm hoping I may bounce my ideas about the bus to the homebrew computer community to get your opinions, suggestions, warnings or whatever.

Well, thanks for all of your comments. They are greatly appreciated.

Steve Garcia.

[Fredrik Axtelius]

Hmm, single stepping seems nice but will it work with DRAM? Will they still refresh as needed while the CPU is paused?

--Fredrik

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[Tom Storey]

If you want to single step and use DRAM, you'll need external refresh circuitry. Refresh is tied to the instruction cycle, so no instructions == no refreshing. :-)

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[Alan Cox]

On Tue, 2 Mar 2021 at 17:18, Tom Storey <t...@snnap.net> wrote:

If you want to single step and use DRAM, you'll need external refresh circuitry. Refresh is tied to the instruction cycle, so no instructions == no refreshing. :-)

Or for most use cases wire a Z80 CTC output to your NMI line. Not quite true single step but pretty close and often more useful.