Flea86 Retro Gaming Project - Progress Update

Valentin Angelovski's picture


Hi All,

Well, a few things have happened since my Flea86 project introduction from the previous month. This month's latest update will cover the following :

1) Completion of Flea86 case design transfer to CAD.

2) Inclusion of EGA (planar) video support for Flea86.




Completion of Flea86 case design transfer to CAD.

After several false-starts, I have finally managed to obtain a transfer of my original case design to digital form. (click on the initial exploded view image at the beginning of the blog, or alternatively here)

Converting the mechanical design to CAD will allow for easier production of the Flea86 i.e. no more melting plastic with a heat gun! ;-) Should be interesting to see what these things end up costing..


Inclusion of EGA (planar) video support for the Flea86.

Basically, while the tandy graphics are nice, support for this adapter isn't as widespread amongst classic DOS games as EGA - in fact, there were a number of so-called VGA games actually used the EGA screen modes!

Given the above, I decided to at least attempt to write a suitable EGA video driver for the Flea86. Reasoning behind this was if for whatever reason I was unsuccessful, I could always reinstate/improve the tandy graphics for the 16-colour modes.. Attempting EGA on an 8-bit micro turned out to be quite a major effort, probably more than I had bargained for..

Well the results are in - and they're mixed :-/ On the plus side, I managed to get a crude 128K EGA setup to display the following color screen modes on the Flea86 (all 16-color derived from a palette of 64):

Thexder 1 - EGA 640x200 mode screenshot:


Arkanoid EGA - EGA 640x350 mode screenshot:


Digger Remastered - EGA/VGA 640x400 mode screenshot:


Also, my fears of a 'massive slowdown' arising from this implementation turned out to be largely unfounded (will post a video on this shortly):

On the minus side, I had to remove code for the mode 13h (256-colour 'chunky' screen) as well as the 16-color Tandy modes to make room for EGA.. :-( In addition, for technical reasons the higher (350-400 line) resolution modes must be interlaced on the Flea, causing some noticeable display flicker (there are methods that can be applied to minimize this however).

Assuming EGA is the way forward, there's still much to be done in terms of better compatibility, font support etc. etc. I would be interested to hear your thoughts around this.

Ok, that's it for this blog episode - Happy Gaming! :-)

Valentin Angelovski

Comments

Mark Vergeer
Mark Vergeer's picture
Offline
Joined: 01/16/2006
Amazing stuff!

This project is simple amazing. I would love to see some videos on it to see it working in action. I reckon you have little space both in memory and power to work with so getting the most out of this in terms of compatibility and usability is a very nice challenge.

Re-implementing something as complicated as a PC for retrogaming is quite a huge project. VGA would be the most compatible mode I guess also for older games but if the device is targeted at real early 8086/8088 4.77Mhz Hercules/CGA/EGA games then EGA would be the most compatible mode.

n/a
Valentin Angelovski
Valentin Angelovski's picture
Offline
Joined: 12/24/2010
Video demos and EGA

Hi Mark, thanks for your comments!

Mark Vergeer wrote:

I would love to see some videos on it to see it working in action.

I for one would love to post a 'fifty games in five minutes on the flea86' video or something along those lines. Of course, once again as I did before with my older 'DX-Demo' videos, I will need to use purchased/donated legitimate game titles - so this may take some time.. I welcome any other workable suggestions for this.

Mark Vergeer wrote:

I reckon you have little space both in memory and power to work with so getting the most out of this in terms of compatibility and usability is a very nice challenge.

You're quite right - writing emulators in miniature is kinda like playing a chess game, but in three dimensions instead of two :-)

Mark Vergeer wrote:

Re-implementing something as complicated as a PC for retrogaming is quite a huge project. VGA would be the most compatible mode I guess also for older games but if the device is targeted at real early 8086/8088 4.77Mhz Hercules/CGA/EGA games then EGA would be the most compatible mode.

I would be inclined to agree, though I guess the problem that I see here is that EGA will take some time (probably on the order of months at my current rate) to achieve maximum possible compatibility. Even then the physical limitation of the video RAM will still be 128K, unless I come up with some clever hack to reach into the UMB for the additional VRAM.. :-/

EGA sure is an interesting beast: for one thing I didn't know that EGA cards were (due to it's attribute controller) considered one of the first (very crude) 'graphics accelerators' for the PC..

Cheers Valentin

Bill Loguidice
Bill Loguidice's picture
Offline
Joined: 12/31/1969
You raise some good

You raise some good questions, Valentin. Personally, I'd rather have perfect Tandy compatibility than imperfect EGA compatibility. If you can somehow work your wizardry to perfect EGA, then obviously that's better, but to me, the reality is even with "only" Tandy support (and presumably perfect CGA and monochrome), you're still talking a huge number of games. You may want to do VGA/EGA in a hypothetical future "Super Flea86" where you have a bit more power/room...

n/a
Valentin Angelovski
Valentin Angelovski's picture
Offline
Joined: 12/24/2010
Re: TGA over EGA

Hi Bill, thanks for the comments!

Bill Loguidice wrote:

You raise some good questions, Valentin. Personally, I'd rather have perfect Tandy compatibility than imperfect EGA compatibility. If you can somehow work your wizardry to perfect EGA, then obviously that's better, but to me, the reality is even with "only" Tandy support (and presumably perfect CGA and monochrome), you're still talking a huge number of games.

Biggest limitation with the current Tandy video emulation on the 'Flea is that it doesn't currently support multiple screen pages - though this may be far easier to rectify than starting again with EGA. Of course, would be nice to see this neat little project in the hands of gamers sooner rather than later.. :-)

Also lacking from the Tandy graphics on the Flea is a 640x200 color mode, due to insufficient room in the code space - unless I take out VGA Mode 13h. I should also note that VGA Mode 13h does not currently include text support.

Bill Loguidice wrote:

You may want to do VGA/EGA in a hypothetical future "Super Flea86" where you have a bit more power/room...

I guess it wouldn't be a bad idea, to reserve EGA/VGA for use on a faster/more powerful hardware version further down the road.

Cheers, Valentin

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.