Re: Ideas for a simple, but somewhat extendable computer bus
If you need simple arbitration, there is always this: https://www.retrotronics.org/arbiter/ -Alan On 2017-11-17 20:11, Jim Brain via cctalk wrote: I'm currently working on a single board computer system, designing from scratch partially as an education experience, and also as something that might be of interest to others. I've laid out the first version of the SBC, and I realize it would cost nothing to add an edge connector on the PCB, allowing expansion options. As well, assuming the design has any merit, I can see creating one of these SBcs for each family (8080/Z80, 65XX, 68XX, and maybe even 16 bit options like TMS9900, 68K, etc.) However, as the design is not *for* any purpose, and I've never designed a bus that could be shared among multiple CPUs, I am wondering what bus layout would satisfy the following criteria: * At least enough to support a traditional 8 bit CPU (A0-15,D0-7, RESET, READ/WRITE,CLOCK,INTERRUPTS) with potentially a few more address bits (A16-23) * Minimal number of bus signals to support multi-processors and peripheral cards, but not so few that usefulness is severely crippled * Easy to implement (minimize need for logic that serves to solely handle the bus) * (If 16 bit data bus is part of the design): Easy for 8 and 16 bit CPUs and peripherals to share the bus (Maybe this means 16 bit units need to be constrained to 8 bit, not sure) * Works out to a size that I can buy edge connectors cheaply (62 pin .100" connectors are looking like my cheap option at present) I looked at home computer busses (Atari, Apple, Commodore, Tandy, TI) for a bit of inspiration, but they all seem overly simplistic (not horrible, but hate to just punt on the idea). I also looked at the ISA bus and the S-100 bus, but they are a bit overwhelming to me (I can grok all the signals, but ensuring they are all responsive seems like it will drive more logic be on the PCB jsut to handle the bus, and I am trying to keep costs very minimal). Thus, Is there a bus (or a fraction of a bus standard) that I should consider to accommodate the above? Anyone else interested in this idea and in a collaborative mood? Jim
RE: Ideas for a simple, but somewhat extendable computer bus
> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of emanuel > stiebler via cctalk > Sent: 18 November 2017 07:47 > To: Jim Brain ; General Discussion: On-Topic and Off- > Topic Posts > Subject: Re: Ideas for a simple, but somewhat extendable computer bus > > On 2017-11-17 18:11, Jim Brain via cctalk wrote: > > I'm currently working on a single board computer system, designing > > from scratch partially as an education experience, and also as > > something that might be of interest to others. > > > > I've laid out the first version of the SBC, and I realize it would > > cost nothing to add an edge connector on the PCB, allowing expansion > > options. As well, assuming the design has any merit, I can see > > creating one of these SBcs for each family (8080/Z80, 65XX, 68XX, and > > maybe even > > 16 bit options like TMS9900, 68K, etc.) > > You know this projects? > > https://en.wikipedia.org/wiki/N8VEM Now :- https://www.retrobrewcomputers.org/doku.php Dave
Re: Ideas for a simple, but somewhat extendable computer bus
On 11/17/2017 07:11 PM, Jim Brain via cctalk wrote: I looked at home computer busses (Atari, Apple, Commodore, Tandy, TI) for a bit of inspiration, but they all seem overly simplistic (not horrible, but hate to just punt on the idea). Is the multi-CPU stuff important initially? If not then maybe keep things simple, but reserve a chunk of pins for "future expansion" with that in mind (or take the approach of various manufacturers and run the 'extra' stuff through to the boards separately from the backplane as/when it became necessary) Alternately, STE immediately sprang to mind (it's 8 bit, but plenty of boards using 16 bit CPUs existed so long as they could handle data 8 bits at a time). Hazy memory is telling me there's some issue with 6502 CPUs, but pretty much any other 8-bitter (as well as m68k, ns32k etc.) is fair game. You could homebrew your own boards then, but also make use of all the hundreds of different commercial ones which existed. If I remember right STE was essentially a simplified version of VME though, so that's probably worth a look too (I think someone else already mentioned it) - presumably there's more complexity and cost involved. cheers Jules
Re: Ideas for a simple, but somewhat extendable computer bus
On 11/18/2017 1:46 AM, emanuel stiebler wrote: On 2017-11-17 18:11, Jim Brain via cctalk wrote: I'm currently working on a single board computer system, designing from scratch partially as an education experience, and also as something that might be of interest to others. I've laid out the first version of the SBC, and I realize it would cost nothing to add an edge connector on the PCB, allowing expansion options. As well, assuming the design has any merit, I can see creating one of these SBcs for each family (8080/Z80, 65XX, 68XX, and maybe even 16 bit options like TMS9900, 68K, etc.) You know this projects? https://en.wikipedia.org/wiki/N8VEM I've followed the N8VEM project for many years, but I had forgotten about looking at their bus design. Thanks. -- Jim Brain br...@jbrain.com www.jbrain.com
Slightly OT: Computer internals book recommendations
The fascinating discussion Jim just started on buses got me thinking again about a book I've been trying to track down for a while. While it's not necessarily classic-computing-oriented, it's not really about newfangled computers either; heck, I encountered it in 2003 or so, so it'd be pretty dated by now. Basically, I'm looking for a certain book (although really any book in the same vein would satisfy), which was on computer system architecture, organization, etc.; it talked about the usual boolean logic, assembly programming in some fictitious instruction set, an overview of two actual architectures (I think at that time they were 32-bit x86 and 64-bit POWER). The other thing I remember very specifically was there was a place near the back (probably an appendix) that talked about one or more specific buses (I think at least PCI was there), with timing diagrams to tell you what was actually going back and forth between the bus and CPU. Like I said, I'm sort of keen on finding the exact book I had, but I realize that's somewhat unrealistic, so I'm open to recommendations on any book like that. And if it can cover the relavant concepts for both classic and newish computers, that would be great. Basically what I hope to learn is how you actually deal with peripherals, add-in cards, etc., on the assembly language level, and what that really translates into on a signaling level. I only really know a little about how to do that in memory-mapped IO systems like the Commodores (and to be honest I don't understand how the buses work there, just how to poke and peek.) Thanks! -- Eric Christopherson
Re: Sync on Green RGB video
On 2017-11-18 14:09, Douglas Taylor via cctech wrote: > I have a couple of vaxes that output 'unique' video, Alpha 3000 300, > Alpha 3000 400, Vax 4000 VLC, and Vax Station 3100 M76. > > The Alpha and VLC each have a 3W3 type of connector and the 3100 has a > 15 pin DEC designed connector. The 3w3 cables are actually still easy to find. I use then, a vga-BNC cable with some adapters > What does it take to connect these to inexpensive, modern VGA light > weight monitors? There are some brands, which support sync-on-green (HP, Viewsonic, that's what I have)
Re: Sync on Green RGB video
You might be surprised how many LCD monitors support SoG. I have several iiyama LCD panels which work fine with a 3100. Aaron. Douglas Taylor via cctech writes: > I have a couple of vaxes that output 'unique' video, Alpha 3000 300, > Alpha 3000 400, Vax 4000 VLC, and Vax Station 3100 M76. > > The Alpha and VLC each have a 3W3 type of connector and the 3100 has a > 15 pin DEC designed connector. > > What does it take to connect these to inexpensive, modern VGA light > weight monitors? > > Doug
Sync on Green RGB video
I have a couple of vaxes that output 'unique' video, Alpha 3000 300, Alpha 3000 400, Vax 4000 VLC, and Vax Station 3100 M76. The Alpha and VLC each have a 3W3 type of connector and the 3100 has a 15 pin DEC designed connector. What does it take to connect these to inexpensive, modern VGA light weight monitors? Doug
Re: Sync on Green RGB video
On Sat, 18 Nov 2017 18:44:07 -0500 william degnan via cctech wrote: > On Nov 18, 2017 4:09 PM, "Douglas Taylor via cctech" > wrote: > > > > I have a couple of vaxes that output 'unique' video, Alpha 3000 > > 300, > Alpha 3000 400, Vax 4000 VLC, and Vax Station 3100 M76. > > > > The Alpha and VLC each have a 3W3 type of connector and the 3100 > > has a 15 > pin DEC designed connector. > > > > What does it take to connect these to inexpensive, modern VGA > > light > weight monitors? > > > > Doug > > > > I have played around with that problem. If you have a converter to > get into a VGA port a newer high-end vga display will be able to > adjust, but not a cheap one. Because I use my vice vga/digital > display for mode stuff, I use a huge SGI color display for all of my > 3w3 outputting systems and I just switch the cable around. If you > could imagine 5 or 6 systems clustered around the one display. > > I am sure someone here has a technical explanation, but in a nutshell > the 3W3 world signal isn't the same as a standard vga and cheap vga > displays can't handle the refresh rate. Someone will prob. refine my > answer but that's why you can't just stick an adapter on there. > > Bill Degnan > twitter: billdeg > vintagecomputer.net The "issue" is "Sync-on-Green". Many *NIX and DEC systems that have RGB output do NOT use a Hsync signal - but rather sync is placed on the "Green" channel. If you use any monitor capable of "sync-on-green", and it should work. Best, Lyle -- Lyle Bickley AF6WS'73 http://bickleywest.com "Black holes are where God is dividing by zero"
Re: Sync on Green RGB video
On Nov 18, 2017 4:09 PM, "Douglas Taylor via cctech" wrote: > > I have a couple of vaxes that output 'unique' video, Alpha 3000 300, Alpha 3000 400, Vax 4000 VLC, and Vax Station 3100 M76. > > The Alpha and VLC each have a 3W3 type of connector and the 3100 has a 15 pin DEC designed connector. > > What does it take to connect these to inexpensive, modern VGA light weight monitors? > > Doug > I have played around with that problem. If you have a converter to get into a VGA port a newer high-end vga display will be able to adjust, but not a cheap one. Because I use my vice vga/digital display for mode stuff, I use a huge SGI color display for all of my 3w3 outputting systems and I just switch the cable around. If you could imagine 5 or 6 systems clustered around the one display. I am sure someone here has a technical explanation, but in a nutshell the 3W3 world signal isn't the same as a standard vga and cheap vga displays can't handle the refresh rate. Someone will prob. refine my answer but that's why you can't just stick an adapter on there. Bill Degnan twitter: billdeg vintagecomputer.net
Re: Sync on Green RGB video
On 11/18/2017 3:44 PM, william degnan via cctech wrote: On Nov 18, 2017 4:09 PM, "Douglas Taylor via cctech" wrote: I have a couple of vaxes that output 'unique' video, Alpha 3000 300, Alpha 3000 400, Vax 4000 VLC, and Vax Station 3100 M76. The Alpha and VLC each have a 3W3 type of connector and the 3100 has a 15 pin DEC designed connector. What does it take to connect these to inexpensive, modern VGA light weight monitors? Doug I have played around with that problem. If you have a converter to get into a VGA port a newer high-end vga display will be able to adjust, but not a cheap one. Because I use my vice vga/digital display for mode stuff, I use a huge SGI color display for all of my 3w3 outputting systems and I just switch the cable around. If you could imagine 5 or 6 systems clustered around the one display. I am sure someone here has a technical explanation, but in a nutshell the 3W3 world signal isn't the same as a standard vga and cheap vga displays can't handle the refresh rate. Someone will prob. refine my answer but that's why you can't just stick an adapter on there. Bill Degnan twitter: billdeg vintagecomputer.net The 13w3 Sun and the like world of video is different than the three wire sync on green video from Dec. There is a feature on a lot of the Sony displays, including the ones that Dec rebadged that supported the sync on green. There is a Raritan converter for Sun keyboard and video conversion to PS2 and VGA that is powered off the 13W3 connector to solve the problem for the Sun systems. Also note there is a monochrome option with just a single coax populated in the 13W3 for sun. I'm currently getting ready to hook it up to the above noted converter, can report back whether it works. FWIW the system is an IPC Sparc 1 mini system. I have the DEC Sony monitor, and a friend and I are collecting information to make a general DEC Vax sync on green / Pro 3xx / Rainbow / Decmate board / jumper board / connector adapter for all the crap we have. Output will be VGA. Right now we've run the video to regular RS-170 monitor. Levels weren't necessarily happy with direct connection but video showed up. thanks Jim
Re: Ideas for a simple, but somewhat extendable computer bus
On Fri, Nov 17, 2017, ben via cctalk wrote: > On 11/17/2017 6:59 PM, Chuck Guzis via cctalk wrote: > > On 11/17/2017 05:34 PM, Jim Brain via cctalk wrote: > > > > > It does not have to be fast. I rather thought, "what is the simplest > > > multi-cpu shared bus that could be easily understood by folks and allow > > > them to focus on multi-processing education, not bus understanding" > > > > How about a serial bus? Physically simple and not too awful logically > > today. Say, I2C or SPI... > > > > --Chuck > > Say USB-version 101101100 :) Sorry to be dense, but are you referring to some actual USB version? Or did you mean something like "one of the many USB versions, some not yet released"? (101101100 is 364 in binary, but I don't see the significance of that.) > > I would say use a 68000 if your still can get them, > but run with a 6800 style clock. The master CPU and > shared memory on the high phase of the clock. The > slave CPU's on the low clock PHASE (clocked by a inverted clock). > This will give you multi-processing with a bit more than > 64KB. > Ben. -- Eric Christopherson
Re: Ideas for a simple, but somewhat extendable computer bus
On 11/18/2017 1:46 AM, emanuel stiebler wrote: On 2017-11-17 18:11, Jim Brain via cctalk wrote: I'm currently working on a single board computer system, designing from scratch partially as an education experience, and also as something that might be of interest to others. I've laid out the first version of the SBC, and I realize it would cost nothing to add an edge connector on the PCB, allowing expansion options. As well, assuming the design has any merit, I can see creating one of these SBcs for each family (8080/Z80, 65XX, 68XX, and maybe even 16 bit options like TMS9900, 68K, etc.) You know this projects? https://en.wikipedia.org/wiki/N8VEM Looking at the schematic for the ECB, I cannot find any description of the signals BAI, BAO, IEI, and IEO. Can anyone shed some light on the function of these signals? Jim -- Jim Brain br...@jbrain.com www.jbrain.com
Re: Slightly OT: Computer internals book recommendations
> On 19 Nov 2017, at 10:57, Eric Christopherson via cctalk > wrote: > > Basically, I'm looking for a certain book (although really any book in > the same vein would satisfy), which was on computer system architecture, > organization, etc.; it talked about the usual boolean logic, assembly > programming in some fictitious instruction set, an overview of two > actual architectures (I think at that time they were 32-bit x86 and > 64-bit POWER). The other thing I remember very specifically was there > was a place near the back (probably an appendix) that talked about > one or more specific buses (I think at least PCI was there), with timing > diagrams to tell you what was actually going back and forth between the > bus and CPU. > Sounds like either Computer Architecture: A Quantitative Approach by David Patterson and John Hennessy Computer Organization and Design: the Hardware/Software Interface by David Patterson and John Hennessy I see there’s a MIPS edition of the second book. My copy of the second book has Hennessy as the first author. Time for a re-read - it’s been a while since I read both of them. Huw Davies | e-mail: huw.dav...@kerberos.davies.net.au Melbourne| "If soccer was meant to be played in the Australia| air, the sky would be painted green"
