F18A MK2

F18A MK2 Isometric

Introduction

The F18A MK2 is the next iteration of the 9918A VDP replacement project I started back in 2011.  When I first set out to make the F18A one of my primary goals was to have the board be the same size as the original 9918A VDP, which means fitting in a 600-mil wide, 40-pin DIP package.  Due to the limitations of PCB manufacturing available to hobbyists at the time, and my lack of experience in PCB layout, I was not able to attain that goal.

Old Problems

The first F18A is almost twice as wide as the 9918A VDP, which makes it a problem when installing in some of the various systems that used the original 9918A/9928/9929 VDP.  Some of the systems placed the VDP very close the perimeter of the main board, or had tall components next to the VDP IC.  Another problem was the VGA header, which protrudes from one side of the F18A board and makes it even wider.

F18A vs 9918A

Here you can see an examples of the F18A not fitting in a Memotech 500 MSX1 computer, and the problem fitting the F18A into the ADAM computer, which required an additional special PCB to offset the F18A.

Memotech 500

F18A not fitting in the ADAM

F18A ADAM Adapter

I made the adapter for the ADAM, but I soon realized I would not be able to make adapters for all the possible systems where the F18A could be used.  It was very frustrating for me, and I’m sure for some users of the F18A.  I also decided to offer two styles of PCB pins to help get the F18A “up and over” neighboring components in some systems, particularly the ColecoVision console.  You can see here the “Tall Pins” vs “Short Pins” options next to examples of the original VDP from various systems with heat-sinks attached.

F18A Pin Options

Availability and New Beginnings

I have always tried to keep the F18A available for the community as long as there was a demand.  Since 2012, 550 F18A boards have found homes in retro-computers of all kinds.  Since this is a hobby for me, when I run out of F18A boards I have to wait for there to be enough demand to have another 100 boards made.  That is about the minimum quantity to keep the costs “reasonable”, so there was always a period between runs when I would not have any F18A boards available.

In May 2017 I ran out of my last batch for boards.  After a month or so I had not received any requests for more boards, and I thought maybe the F18A had run its course and the market was saturated.  Apparently everyone who wanted an F18A had one.  It was not until early August that I received a request for a board, and come November it had only crept up to about 50 requests.

It was at this point that I started to seriously consider the MK2.  Since it had taken almost 6 months to get up to 50 requests, I speculated that it would probably take another 6 months to reach 100 requests.  If the demand stayed linear then that would give me time to produce the MK2.

Compared to 2012, the PCB capabilities available to hobbyists now in 2018 have become pretty amazing.  Specifications that I could only dream about in 2011 are typical now.  I attribute a lot of this to the cell phone industry which is constantly pushing the size of electronics down, and the density of PCBs up.  When PCB houses update their capabilities to support big industries, the benefits trickle down to the rest of us.

Also in the 5 years since I chose parts for the F18A, the cost of FPGAs has come down as well.  Today I can get a Spartan-6 FPGA, with more than twice the capability as the Spartan-3E I used for the original F18A, for less than I can get the Spartan-3E!  The Spartan-6 opens up a lot of capabilities to making the features I need in the MK2 possible.

With the necessary part costs now within the realm of possibility, the PCB capabilities available to make the MK2 board the same size as the original VDP, and the increasing demand for another runs of boards, it was time to make the MK2 a reality.  Thus I began work on the F18A MK2 in earnest.

Apologies

At this point I would like to apologize to everyone who has been patiently waiting (and still have to wait a few more weeks) for an F18A board.  I do not like to release vapor-ware, and until I had a working MK2 prototype I was not going to mention the new design.  If I could not get pull off the new design, I would just make another run of the original F18A board.  So far that has not been necessary, I hope no one is upset, and I really believe the MK2 will be worth the wait.

F18A MK2 Features

This is the candy portion of the story: the feature list.  The MK2 was designed to solve some specific problems, as well as add new features to allow it to be used in more systems (future plans), or as a general purpose FPGA development board.  Two of the most obvious features are the Digital Video output (TBD, most likely DisplayPort) and the size of the board.

I’m sure some people will be unhappy about the Digital Video output instead of VGA, but it was probably the single biggest complaint / comment about the original F18A.  I believe the first thing most people do is get a converter for the F18A to go from the VGA output to Digital Video.  Also, the availability and small size of the cables and connectors made a digital format a simple choice to make.  Modding cases will be easier for people, plus the audio problem is solved for those who can manage to hook up a single wire in their system.  For those who still want or need VGA, Digital Video to VGA converters are available to fill that requirement.

The primary features of the MK2 over the original F18A, as related to the 9918A family of VDPs are:

  • The MK2 is 52mm x 19mm, which means it is the same size as a standard 600-mil 40-pin DIP socket.
  • No pin-options are required for various systems.
  • The MK2 outputs native Digital Video via an on-board connector.
  • The MK2 has an audio input pin that can be used to inject the host computer’s audio into the Digital Video signal.
  • The MK2 powers-on much faster and should not cause problems for computers with short Power-On Reset circuits.
  • Dual-voltage level shifting is used for all host-system inputs and output pins.

The MK2 will run the same core as the original F18A, and I am also committed (and still working on) fixing certain firmware problems with the original F18A.

New features of the MK2 that will make it possible to replace other VDPs in the near future:

  • The MK2 has 512KiB of on-board SRAM that will be usable as VRAM.
  • There are 14 general purpose 3.3V IO pins available, in addition to the standard 9918A host interface pins.
  • Mode-1 pin for 9938-compatible retro-fitting in a 9918A-based system.
  • Standard JTAG interface.
  • More than double the FPGA resources in the Spartan-6 LX9 over the Spartan-3E used in the original F18A.

Some trivia and technical-specs for the curious:

  • The MK2 schematic and PCB was created with KiCAD V4.0.7
  • All prototype PCBs were made by OSHPark
  • The MK2 requires 5/5-mil trace/space for escaping the FPGA and routing the SRAM
  • The FPGA is a 255-pin BGA with 0.8mm pitch
  • All the capacitors are 0402 ceramic (that’s 1.0mm x 0.5mm!)
  • There are 6 level-shifters on the board, 5 are on the bottom and are 1mm x 2mm 8-pin, 0.5mm pitch BGA
  • The voltage regulators on the board are the same as some used in the iPhone-6s, only I used the larger SOT-23 package
  • I assemble the prototype boards myself using a home-made reflow oven for the BGA ICs, and hand solder the reset with hot-air
  • I use a 70x stereo microscope for soldering / assembly
  • The MK2 uses about 120mA when operating normally

Here are some renderings and photos of the actual prototype:

F18A MK2 Top

F18A MK2 Bottom

F18A MK2 Proto Iso

F18A MK2 Proto Bottom

F18A MK2 Proto vs 9918A

Status

As of this writing, the MK2 is currently in prototype testing.  Almost all the new features are tested and working, and I am currently waiting for the revision “H” (yes, that is EIGHT prototype revisions) PCBs to arrive from OSHPark.

I would like to take a moment to say “thank you” to OSHPark!  They are an awesome service and have made this whole project possible thanks to their affordable prices, easy to use website, and great PCB capabilities.

Once the final PCB prototype is proven working, I will email everyone on the waiting list and open my web store for pre-orders.  Based on the actual orders made by people, I will place the order with the PCB manufacturer to have the MK2 built in quantity (the scary part).  Last time the manufacturing took about 2 or 3 weeks.  Once I get the boards I will program, test, and ship them out.

I expect to get the lasted PCB back in about 10 days, and I will do the assembly and testing.  So if everything to according to plan, I hope to be able to place the big order sometime in July.

Since I have gone ahead and announced this new board, I will also be trying to keep the status updated more regularly.  As of right now I plan to post the on-going status in a thread on the Atari Age forums, in the TI-99/4A subforum (https://atariage.com/forums/forum/119-ti-994a-development/)

Atari Age is my primary retro-computer hang-out, and there is a great community and a lot of information there.  I highly recommend you check it out if you have any interest in retro-computing of any kind.

47 comments to F18A MK2

  • John Messeder

    Great news, love the HDMI feature too!

  • Ricky Dean: Bottoms

    Matthew, I want one!! RickyDean on atariage.

  • Jeff Stimson

    Oooooh, I’m gonna want 2. One to replace the current F18a in my TI, and another for my Adam. Does this qualify as a request to be put on the waiting list?

  • Duane LaGrange

    Way cool! I think I’m committed to two of the F18A Mk1’s. I hope that means I’m still in line for two of these! Man, this is exciting!

  • Stephen Gillespie

    Can I please be put on the waiting list.

  • Victor Steerup

    I have original F18 and it works well, does everything claimed. Would like replacement for T.I.M. Does “9938” compatability mean I would need S.O.B. for a TI? Would like to use X80, XHI, YAPP, Funnelweb DR90 and EA90 again. Thanks for all of your hard work on this project.

    • matthew

      The MK2 will not have 9938 functionality for a while. The first release firmware will have the same core as the current F18A. I’m not sure 9938 + F18A-enchancmetns can be made to co-exist, I’m still working out the possibilities. At the very least I plan to produce a 9938/58 specific firmware for the MK2.

  • Colin Little

    Please add me to the list for a MK2, looks really interesting !!!
    Colin

  • Bryan Shearer

    Count me in for one of the new MK2!

  • Ron

    Thank you so much for the update — very exciting for sure! I’m glad I’m on your backorder list!

  • iKarith

    If you have micro-HDMI to panel mounted HDMI boards, I’m totally on board with HDMI. Faster hookup. Audio still out the back? Also, if someone has a Mk 1 installed, is the Mk II going to leave a big hole in their case? One of the cool things about the VGA connector being on a PC slot blank was that it could be installed on some systems (TI-99/4A) in such a way that hid unsightly case cuts.

    Conveniently my Dell 2001fp and 2007fp already have HDMI installed (via adapter) as I don’t like DVI cables much. No audio that way, unfortunately, but most of my HDMI sources have no audio anyway.

    • matthew

      Case mods and such are totally up to the user. Adapting from the MK2 video connector to a back-plane or just going through the case and using a wire-clamp strain relief, etc. is up to the end user.

  • Art Cate

    Put me down for one

  • matthew

    Please use the contact form to request to be put on the MK2 mailing list. The comments are for, well, comments related to the post. Thanks. Matthew

  • Jim

    Awesome work! Can’t wait to get it!

  • Why are you so awesome?

    Can’t wait to add this to my TI.

  • Marten Feldtmann

    I would be very interested in this add-on. How much is it and how is it added to a specific Z80 computer system ? Does it connects like the original video chip ?

    • matthew

      I’m not sure what the final cost will be yet, I’m still finalizing the video output since certain formats require licensing the technology.

      As for interfacing with a Z80, it should be very easy, and the circuit would be exactly the same as the original TMS9918A VDP, except you don’t need anything except the host interface connections: CD0..7, #CSW, #CSR, MODE, INT, RESET, +5V, GND. I have a post here on my website that gives the F18A pin out, and the MK2 will be very similar. You can also look at the MSX1 systems for an example, or the ColecoVision; both of those systems are Z80-based.

  • Jordi

    “and I am also committed (and still working on) fixing certain firmware problems with the original F18A”

    Does that also include the problems PAL users have been encountering with some games freezing or not booting? That would be awesome!

    • matthew

      That is pretty much exactly the problems I’m trying to resolve. It has been very hard to find the problem though, even with a logic analyzer. I’m still working on it though.

  • Richard Balkins

    I got to get one for the TI-99/4A and maybe even one for my Apple IIgs (could I be a little evil there…. lol) and the GreenArrays EVB-001 where F18A has a little different meaning as those being the F18A (18-bit Forth computers on a chip) nodes in the GA144 (which is a chip that has 144 of these 18-bit Forth computers).

  • Robert Webb

    I’d like to purchase 2 of the F18A MK2 devices. Please put me on “the list”. Thanks! Your work is great.

  • Joshua Lindahl

    I am interested in the F18AMk2 as well. Just got a retro computer lot on 7/14 which luckily had a TI99/4A (my family’s first computer when I was kid). Seems to turn on and outputs to my LCD TV (made my own component cable from the RF adapter DIN plug).

  • jaysunten

    Will this work with the Baby Pac Man Vidiot board? It would be nice to install a flat screen in my pinball machine.

    • matthew

      It should work, but I have never had access to a Baby PacMan to try. The F18A is electrically compatible with the 9918A/9928/9929 so I am very confident it will work.

  • Pavlos Katsaros

    I am in for an f18a board for my ti99/4a old or new.
    Please countme in

  • Michael MacDonald

    Was in Atari age forum, and I don’t think I’m at all wrong on this. You’re not the manufacturer of this part. You are the designer. The company you hire to fabricate and assemble the PCB are the manufacturers. They are the ones who would have to have the HDMI license.

  • Michael MacDonald

    Also, I would like to be put on the waiting list :D. I just got a reply back from HDMI.org, and they confirmed that if you have your board manufactured someplace that is HDMI licensed, you should be fine. I hope that helps, but if it doesn’t, I’m sure you’ll figure something out :D.

  • Gregg Eshelman

    I suspect many people would be happy with a true bitmap mode for 256×192 graphics. Even if only accessible via assembly language programming, that would make much better looking games possible on the TI-99/4A and MSX-1 computers.

  • Stu Birchall

    Would like to be added to the MK2 mailing list, and would love to order one when it’s available. thanks.

  • Ted Niespodziany

    Matt:
    First sorry, I requested an F18A and your response slipped by me.
    Great news on the MKII!! was thinking the F18 would slip into obscurity, not so with the MKII

    Put me down for 2 please

    Also I am writing F18 drivers for the 6809, will post a link when the bugs are worked out.
    For the other poster, i know someone that wants to try these in super pac and baby pac.
    Will post that also when we get the time to try.
    Thanks agian

  • Jeff Carbello

    Oh, my F18A is still sitting in the ziplock package on my shelf waiting to find an install local. But really would love an HDMI version for Adam.

  • Cal Odom

    I’m on the list…. but I want to be sure its the list for this one! Amazing improvements!

  • Cal Odom

    Im on the list, hopefully for this model! I left another comment but I think I included the wrong email address that I listed earlier. Impressive improvements with this model! Can’t wait to see it available!

  • Joseph Carter

    Just wondering if you had an updated ETA,, I know you want this thing to be solid when you release it!

  • Andrew Arthur

    Hi Matt, it’s just become known to me that ColecoVision/ADAM users may want to be able to change option switch USR 1 on the fly. As such, would it be possible with the F18A Mk2 to make it easy for the installer to be able to connect USR 1 to a case mounted on/off switch? The reason for this is that in many games the flicker is horrendous and as such setting USR 1 such that it takes advantage of 32-sprites-per-scanline is great. However, some games take advantage of the original VDP limitation of 4-sprites-per-scanline to mask sprites as necessary. An example of the latter is in Antarctic Adventure, when the penguin falls in a crevasse, the bottom of the penguin is hidden inside the crevasse and looks correct with the 4-sprites-per-scanline limit. However, if USR 1 is set to 32-sprites-per-scanline then when the penguin is in a crevasse, the whole body can be seen including its lower half that should be masked. Therefore, being able to easily switch USR 1 based on what game is being played, via a case mounted switch, would be a great feature to be able to implement.

    Would love to know your thoughts on this.

    • matthew

      The jumpers on the original F18A, and the switch on the MK2, pull an input to ground if the jumper is on or if the switch is closed (in the case of the MK2). If the jumper is off or the switch open, the input is pulled up via a weak pull-up in the FPGA. This makes it easy to add a switch to your case if you want that external functionality. For the MK2 this would require soldering a single wire to one pin of the user switch for whatever function you want to control externally.

      Since the sprite limit is also controllable via software, another option would be to write a simple program that allows you to select the sprite limit. The selection will survive a system reset since the external sprite user switch is only checked at *power on*.

  • I am thrilled to see that the F18A is not dead, and the new feature list is wonderful. I’d love to include the F18A mk2 in the next version of my HD63C09 homebrew singleboard computer (original writeup here https://hackaday.io/project/345-hd6309-singleboard-computer ) so please put me down for two F18A mk2 when they become available!

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