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68008 Wire-Wrap Prototype Board for VME

Thanks, Bill. Yes, your quad serial OX16C954 for RC2014 - utsource.net has them for $5.89 - Used - Here: https://www.utsource.net/itm/p/9476127.html

Very nice. I might stick with the basic 68681 for serial first, and then, if I can get that working, then mount an OX16C954 and see if I can get it working. And before I try CF or SD on my own, I will most certainly be looking at Tom Storey's CF card first.

Tom's CF Here:
github.com

COMET/CF_Interface_v2 at master · tomstorey/COMET

A highly integrated, small form factor Motorola 68000 based computer featuring "COM" ports and an "ET"hernet controller, and associated bits and pieces - tomstorey/COMET
github.com github.com

As for the console port, I have been looking at PCI-Express x1 cards and the prices look reasonable except I want to avoid the ones that require a breakout cable. Lose the breakout cable and you have an expensive paper weight. There are a few that use Ribbon Cables instead and that's a lot safer. Things like special cables tend to disappear around here.

As for a Terminal "box" I like this one best:

Legacy Pixels ASCII VT 100 Compatible Terminal Emulator RS232 Serial​

www.ebay.com

Legacy Pixels ASCII VT 100 Compatible Terminal Emulator RS232 Serial | eBay

There is also a USB interface which supports serial over USB and acts as a USB-to-serial converter. - Easily updated firmware. - All new Legacy Pixels designed PCB. - Source code, releases, and case.
www.ebay.com

Just dedicate a keyboard and monitor to it and that should do it for a "stand-alone" terminal.
As for a graphics card, I'm in no rush. However it would be nice to play with a graphics-mode OS Desktop. I saw something related to Tom's Computer and a Graphics OS related to the Atari ?? I think. My memory is poor for details. I have it bookmarked somewhere.
However just getting my board to boot into a ROM Monitor would be a thrill. That's something I have wanted to do since my college days. The whole "A Sage of My Own" idea. 68030 and 32-bit Debian Linux maybe ?? A fella can dream. :-)

Slow but steady progress on VME. :-)
 
transistor said:
I'm not sure I understand what you mean. How would such a terminal card connect to the VME bus besides using it for power? Normally a terminal would be an independent standalone device like the example links you provided. For my own card, I use FTDIs to connect it to my desktop PC via USB, which then shows up as a generic serial port. I can then use pyserial-miniterm or any other serial terminal program to connect to the OS running on the 68030 card. It skips the RS-232 conversion and uses TTL levels to connect the FTDIs to the MC68681 UART controller on the board.

Tom Storey has recently completed a video card for VME which might be the closest to what you're looking for, but I'm not sure he's put the design files up online yet. It has an SVGA connector as well as two PS/2 connectors for a mouse and keyboard, but I don't think he's using those PS/2 connectors for anything yet. I'm planning to eventually make a generic FPGA board that could be programmed for different uses, but that won't be for another year or so. I'm going to respin the CPU board first, but before that I want to get some more progress on the software.
Click to expand...
TransistorFet -
Yes, Regarding Tom Storey's Video Card for VME Bus, I've been thinking about that. Using a serial port, with or without a USB adapter, to communicate with the 68K-Sage - That will be adequate for now, and possibly for a while yet to come, But I have also been thinking about being able to connect to the 68k-Sage to connect to it using graphics.

My line of thought is that I am good talking to a CLI through a serial port, up to a point, but with my Desktop Linux machine, I really like being able to use the GUI. Linux has a Powerful Command-Line but sooner or later I will want more.

Case in point, Tom Storey and his video card and trying to install some kind of GUI - EmuTOS ???

Here: https://emutos.sourceforge.io/

And that's going to my too, preferably sooner than later.

Which Comes back to Linux. I understand using the CLI for Linux admins,
But what I don't know is how KDE Plasma or Gnome GUI Desktop - How do they get all that stuff on the screen ?? Surely not through a complicated "Serial Port". Anyone know ?? Does the OS require that one has a Video Card available that it needs Read-and-Write Access to it ??

And pursuant to this, I have been thinking about what Bill Shen said about how powerful a FAST 6502 CPU can be. So I've been looking at how people are using the WDC W65C02 8-bit CPU to create a Video Card / Terminal or even better use a W65C816 16-bit CPU.

The key is getting a CPU to "Lock-Step" with a 50 / 50 cycle sharing operation mode. First "up" cycle gives access to the CPU and Memory.
And then next in the "Down" cycle, the video text and graphics hardware "owns the bus" and paints the screen.

Examples found on the internet so far tonight:

1. https://6502.co.uk/lesson/graphics-card

2.
 
This is a follow-up of the VGA Card using an overclocked 25.175 MHz W65C02 8-bit CPU above the normal clock rate. That's 25.175 for an 8-bit processor. But for a 16-bit processor divide by 2 = 12.5875 MHz Instead.

However, instead of learning a new CPU Chip and it's assembly language, etc., I would prefer to stick with the 68k-Family. And I've been browsing prices and availability, especially sources of "NEW" Chips. Utsource.net has the low prices and they purport to have "NEW" chips.

A 12 MHz 68EC000 CPU would be just a very "mild" overclock to 12.5875 MHz.

utsource.net == $6.40 for a NEW 12 MHz 68EC000 PLCC.

MC68EC000FN12 Price - MC68EC000FN12 in stock - Buy MC68EC000FN12 on Utsource.net

Description: The MC68EC000FN12 is a microprocessor manufactured by Motorola. It is a 32-bit microcontroller based on the 68000 family of microprocessors. Features:
www.utsource.net www.utsource.net

BUT what if we "Under-Clock" the CPU instead ?? Run a 16 MHz 68EC000 at 12.5875 MHz instead ?? Result is that the CPU is rated for the speed it's running, and then some, and we're pushing out 16-bit words instead of the 8-bit "words" of the W65C02 CPU. The whole timing chain should work out OK, I think. I haven't thought about making a video card in decades so this will take some time. Again, this would be a side-project or at least a second project.

First Project = Is an Ultra-Simple 68008 computer. Using Chips:

1. MC68008FN8 - 8 MHz - PLLC-52 - CPU - 52-pin PLCC to DIP adapter to get it into a Wire-Wrap mode.

2. Flash 512k x 8 Microchip Technology SST39SF040-70-4C-PHE as an EPROM / EEPROM - non-volatile Program Storage.

3. 512k x 8 Static RAM - Alliance AS6C4008-55PIN - 55ns

4. MC68681P DUART

5. Analog Devices / Maxim MAX239 - RS-232 - 3 Out 5 In -
- or - MAX244CQH - 8 Out / 10 In - Handles Both channels of a DUART,
- or - MAX245CPL - Also 8 Out / 10 In.

Either of these last two chips are a bit pricey but the idea of one chip handling all the lines of 2 Serial IO Ports, converting TTL to RS-232 and vice-versa, is Really Very appealing to me.

I know that the USB chips are very popular, but this is s'posed to be a "Retro" computer and the RS-232 is how we really used to do it back in the day. There was no USB Option back then.

For handshaking, the RTS / CTS lines are both there and for a connection to a "real" Modem, the DTR, DSR, DCD, and RI - they are all there, if needed. I see WAY too many serial ports with "missing" signals. :-(

3-Out & 5 In. Or 8-Out (two spares) & 10 In. Please keep in mind that the USB translators DO NOT do the handshaking, or they do so very poorly, and also if you really wanted ALL of the RS-232 lines for ANY reason, they are ALL THERE.

However, I won't be going "all the way back" to the MC1488's and MC1489's. <GRIN>

And for a simple device-select, I think a single 74LS138 could handle all of the devices, each with a 512k x 8 memory map "Bank". For the CPU, The Use of a PLCC to DIP adapter gives me the "extra" address bits needed for a "larger" memory map than is possible with a 68008 DIP chip. The PLCC chip comes with 2 more address lines that the 68008 DIP simply does not have.

Just a few more thoughts today. I think that it would be nice to have a single VME Board that would handle all the "Console IO" including the PS/2 Keyboard & PS/2 Mouse ports. And output at least Monochrome VGA Display signal to a Monitor. And since the Console IO is happening between the Main VME CPU Card and this Secondary "Console IO" VME Card, there would be no need to do Serial connections for the Console IO.

I need to do a LOT more reading on the whole "Using W65C02 CPU as a Video Card Controller" idea and see how, or even if, the same Idea could be used with a 68EC000 16 MHz CPU instead of an 8-bit W65C02 CPU.

My memories of "How do video cards work" are extremely dusty with lots and lots of cobwebs. <grin>

It's Going to take some real studying to figure out how to make this 68EC000 @ 12.5875 CPU work BEFORE getting into any hardware for it.
Do the Math. Figure out the schematic, etc, etc.

And it wouldn't hurt to run this idea past Bill Shen and Tom Storey as it seems like they are already WAY ahead of me on this. I need to understand this.

Enough for today,
HSS
 
48-pin 68008 can map 1 meg space so it is likely enough for your 1st 68K design. It is easier to prototype than 52-pin PLCC, assuming you are going to prototype your design first. I wouldn’t worry about video/keyboard for now; there are lots of things to worry about just get the first 68K design up and running.
Bill
 
Hi, Bill !!

Yes, If I was content to only use part of each memory chip rather than all of it, then Yes, I could use the DIP-48 68008 CPU chip. However, I want ALL of each chip available. Mainly for plenty of space to add to the subroutines in the "EPROM" (Flash). I want to be able to add onto whatever is there already and not have to delete an old section so as to make room for a new section. I'm referring to a 512k x 8 Flash to be used as "EPROM" and a single 512K x 8 Static RAM. Each a single byte-wide chip for the 68008 Data Bus.

So the whole Flash chip becomes a "blackboard" or a "White Board" in which to stuff things in and debug them on real hardware. An Emulator, or Simulator, or "Ship In A Bottle" VM can only go so far.

So those are Devices 1 & 2 - The "EPROM" and the RAM. The 3rd Device == the 68681 DUART. And the 4th is a Real-Time Clock Chip - an RTC. I don't "need" anything more but I might want to add more stuff later. So far, I've only used half of my 74LS138.

On the 48-pins 68008 DIP, If I want access to the Full "EPROM" and the Full RAM, then there's no room for anything else !! Just those two "edge-to-Edge". Done. And Yes, I definitely want access to ALL of the Memory Spaces, and then add 2 devices that are IO but are mapped as memory.

Using a 74LS138, For Example, I can map all of those 4 devices and have room for 4 more devices or memory chips or whatever. For a very long time, (years), I have thought about the 68008 DIP versus PLCC and I keep coming back to these trade-offs shown above. So It's not a matter of me not having thought it all out yet. I have already done so, and I have made my decision. And each time I go over it again, I come to the same results.

But I really do Invite and Want your thoughts and feedback. I have closely watched every 68000-family SBC on RetroBrew and Google-Groups, etc. That you have done. I am also now going over the 6502 world based on what you've said here recently. The Biggest Difference is that you prefer SBC's (mostly) and I have always been a "Bus-Oriented" person, like S-100 / S100, RC2014, RCBus, and now VMEBus - or just VME for short.

And working in the PC world, the ISA Bus, PCI bus, and now the PCI-Express bus.

And this difference between us is just a Vanilla versus chocolate, neither right nor wrong, but rather just different choices, different preferences.

So Please DO continue to give me your feedback. I NEED it. In this world I am SUCH a Newbie.

Thanks again for your time.
HSS
 
Roger
norwestrzh said:
There's a 'EC' variant of the 68000 that's worth looking into, Harry. I've built an entirely homebrew SBC around it. It is very fast. There's a thread about it in this sub-category. I run mine at about 28 MHz!.

I think that I remember seeing some 68k software quite a while ago written by Harry Speer. Is that you?

Roger
Click to expand...

Roger -

Thanks !! I have looked up the 68EC000 and I am Very Grateful for your Tip !! My Ebay and UTSource.Net searches have found plenty of 68EC000 at 10 MHz, 12 MHz, and 16 MHZ,
but the One I am most interested in is the 20 MHz version. An MC68EC000FN20 in NEW condition from utsource.net here: For $8.42 each - now 12:16 PM, 2025-09-30.

MC68EC000FN20 Price - MC68EC000FN20 in stock - Buy MC68EC000FN20 on Utsource.net

Description: 68EC000 Microcontroller Features: - 16-bit microcontroller - 20 MHz clock speed - 64K bytes of ROM - 4K bytes of RAM - 24 I/O lines - 8-bit
www.utsource.net www.utsource.net

PLCC-68 package. I've found some PLCC to DIP adapters that I hope will work well in the Wire-Wrap sockets. Fingers crossed. If not, then I may have to create a bare PCB and send it to a baord fab house.

I'm interested in this CPU as I have been looking at articles by Bill Shen on his "walkabout" in the 6502 world at 6502.org. Specifically a VGA Dot Clock of 25.175 MHz. So a single dedicated "slave" processor for the video card.

Clearly this would be overclocking the 20 MHz 68K CPU chip, but I have read people's posts about how the CMOS CPU chips are more "accepting" of higher than rated frequency. Your own post above, Roger, with your 68EC000 running at 28 MHz is clear evidence that this can be done "safely" and be "stable". (I hope).

This is one possible path to go down, attempting to build my own VME 68k-based Video Card.
So Far, I have not found any "native" VME Video Cards. But then most of the VME cards seem to be in environments where the graphics were not needed. Text alone would suffice.

My serial RS-232 Console: port with text-only is fine for starters and for a text-based OS like CPM-68k. However a GUI OS like EmuTOS is going to need main CPU access to draw graphics in video memory. Tom Storey is definitely headed in that direction. EmuTOS.

The other pathway from this "fork in the road" is to adapt a video card intended for some other bus and "kludge" it to work with a CPU Card in the VME Bus. I have been exchanging emails with Mark Durham (UK) who is successfully using a 68000 CPU Card for the RCBus and he now also has a 68302 CPU Card which conveniently has 3 Serial Ports in it. I greatly admire the work he has done. I'm very impressed.

I've asked Mark if he has any blank boards to spare for the 68302 CPU card, his Version 2 ROM+RAM card that uses pairs of 512k x 8 Flash as "EEPROM", and uses pairs of 512k x 8 Static RAMs. Mark has a third card with Dual 68681 DUART's for 4x Serial IO Channels, though he does not have them converted To / From RS-232. That bit will be mine.

Lastly, There are a few RCBus / RC2014 Video Cards, though I don't know whether or not they allow the CPU to modify the Video Ram over the RCBus from the CPU Card. The Gotcha here is that I would have to convert their Z80 Assembly Language Source Code over to the equivalent 68000 Assembly Language Source Code, and then testing the 68k code until the Video Card works with a 68EC000 CPU - or - end up chucking it because I cannot get it to work. Only after a lot of effort first. I have to believe that success with this "kludge" is possible.

It was really Bill Shen's posts in the Google Retro-Comp Forum that got me headed down the "bare video card" path. His time with the 6502.org people. He came up with what he calls a "VGA65" in an article here:

6502 or Z80 as VGA controller

groups.google.com groups.google.com

On the RetroBrew website, IF you can get in, then see the "VGA65" Here:


Had to shrink it to get it to not break the link. Try this:

builderpages:plasmo:vga65:vga65pcb_r0 [RetroBrew Computers Wiki]

tinyurl.com tinyurl.com

Bill Uses the W65C02, However I am talking about using the - 20 MHz MC68EC000FN20 - overclocked to 25.175 MHz.

However I am thinking about this Video Card and it's CPU as a "Slave Co-Processor" dedicated to just running the Video Card and nothing else. I'm hoping that the 20 MHz CPU overclocked to 25.175 MHz will be stable. On second thought, I might add 1 or 2 USB Adapters to Enable a USB Keyboard and USB Mouse. Or an easier (?) choice of using PS/2 Keyboard and a PS/2 mouse.

A VME Video Card from Scratch is a much more challenging goal than using an mc68681 DUART and use Either a MAX239 - 3-Out and 5-in, enough for 1 channel, Or use a MAX249 - 6 Out, and 10-In, for 2 channels. One MAX249 per DUART. Nice.

I like to dream big but I have also learned to consider seriously my limitations.
 
Nice to see VME bus being used in home brew project now, I just want to share some of my experience from the past and my new hobby projects about it :
- VME is not just an IO bus, it was made for multiple processors sharing memory and/or IO cards, make sure to drive them all pins or some third party boards will not work.
- It uses special bus drivers that can sink up to 64mA ! If you use low power drivers (or standard TTL output of a CPLD ex) it will fail from 6~8 boards or more.
- My first prototype I also made with wire-wrap, took a long time with some mistakes that where difficult to find.
Looking how cheap PCBs are in China today and software like Kicad being free, I would leave the wire-wrap for what it is...

I was designing VME boards with 68k processors 25 years ago, and kept a lot of those old parts all these years to ever use them in a hobby project.
Now I'm creating a 160x100 VME card with a 68360 processor (32bits), believe it or not but ALL parts are thru-hole (original plan for Wire wrap).
These kind of processors (683xx) have build in submodules like serial port and a SystemIntegrationModule so you can leave out a lot of external components
and most have a BDM interface so you don't need a programmer for the EPROMs.

What sort of display are you thinking for your project, text based or graphical ?
I'm also want to create a very simple 3U VME card that will display a 80*40 character display (like on old DOS PC) with 16 colors by using a Dual page RAM and a CPLD.

PS : do you know on the 68EC000 you can select an 8 or 16 bit databus at power-up, the address bus is always 24 bits. Speeds is specified at 16MHz, I got one running at 24MHz.
I do have quit some stock of old new 68k parts, 68EC000-16, 68EC030-25, 68882-25, 68901, 68230, ... I want to sell.

Br,
Steve
 
> Speeds is specified at 16MHz, I got one running at 24MHz.

Right! My EC68000 chip is marked 20 and it runs at ~29. I got an extra ~2 MHz by replacing the 74LS glue logic with 74HC. Not VME however. Description of the SBC can be found below in this group.

Roger
 
There is a 5/3.3v version of 68000, 68SEC000, that works at 5V and 3.3V. It is a more recent part and therefore faster. I have a 68SEC000 mezzanine board for EPM240 development board clocked at 25Mhz at 3.3V. It likely can run 30+mhz at 5V.
Bill
 
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