Tiny 'XT-class' machine

[basman74]

'Tiny XT' Progress Update

'Tiny XT' Progress Update

Hi all,
I have some further news/developments regarding this project (apologies about the late update, though I am still working on it ;-))

1.) 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.



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..


2.) Exploration 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.

Okay, that's it from me on this update - Comments/Flames invited!


Valentin Angelovski

 

[Holmes]

This project looks simply amazing. Great job! Really excellent attention to detail, especially on the case prototype.

I've just got to have one. Count me in when you begin taking orders!

Now I've got thoughts of building a mini-monitor with a little LCD (and maybe some speakers) in it to go right on top of this baby. That would be unbelievably cool.

 

[basman74]

Flea86 - March 2011 status update

Flea86 - March 2011 status update

Well folks, seems I've struck a problem - just as I was about to order the parts for a small run of Flea86 systems, the supplier of the SOC (system-on-chip) used in my design has informed me there is no stock and the minimum order quantity that they are now willing to accept (i.e. > 5,000 pieces) will be considered far too high and costly for this hobby venture.. :shock:

They did at least suggest an alternative, but it's in a different package style with more pins, which means another board re-spin, firmware driver re-write etc..


So my options now are:
1.) (more likely) Using what I currently have available, build up a small batch of, say 10-15 systems for those who may be interested in purchasing a Flea86 XT system?
OR
2.)Start again with new PCB artwork?


Regards,
Valentin
PS: At least a PCB re-spin with the new parts might be a good thing, since the new parts offer an extra discrete 16 I/O pins to configure/play with..

 

[Maverick1978]

You're the man with the know-how... you tell us! While I don't think more than 10-15 people said that they would be interested in a unit, I'm willing to bet that there were other interested parties who didn't speak up.

Perhaps we should start a poll for interested parties both here and maybe at N8VEM to see how much interest there is before you go through the trouble of re-designing the PCB and software?

With that said, I'm definitely still interested no matter which way you decide to go... that unit just looks too sweet!

 

[basman74]

While I don't think more than 10-15 people said that they would be interested in a unit, I'm willing to bet that there were other interested parties who didn't speak up.

Well I would bet that way as well - even in 2011..

Perhaps we should start a poll for interested parties both here and maybe at N8VEM to see how much interest there is before you go through the trouble of re-designing the PCB and software?

Sounds like an idea to me. I could compile a brief spec-sheet on the Flea86 system, both as a web-posting and as a PDF document, which should make it easy for potential users to decide if 'the Flea' is for them.. This shouldn't take me long (allow a day) to have ready in time for the poll..

Doing board re-spins is not so bad compared to software rewrites - those are a real killer.. :cursemad:

Regards,
Valentin

 

[basman74]

Flea86 - March 2011 status update (continued)

Flea86 - March 2011 status update (continued)

Continued from above..

2.) Took some time out to 'play' with the 'FleaBUS-I' control port on the Flea86 using a few homebrew expansion cards along with simple test apps written to suit.

Following is an image of a Flea86 mainboard with a simple analog input daughter-board (built around a TLC-548 IC) installed. The oscilloscope test program was written in MS-QBasic and uses INP/OUT statements to read in the digitized voltage levels from the variable pot (potentiometer):


Click image to enlarge


3.) Inclusion of the 160x100 pixel 'tweak' mode to allow games like round-42, moonbugs and Paku-Paku.

4.) My EGA test module still has many issues left unresolved. These relate to problems integrating the support for those crazy bit-plane modes and also around implementing the hardware CRTC support. Not certain I will be happy with the final outcome, given the very limited resources on the host CPU and also given the TGA module already works sufficiently well for alot less headache..

 

[basman74]

Flea86 Preliminary Specification rev 0.1 released

Flea86 Preliminary Specification rev 0.1 released

Hi all, me again

Okay, here is the preliminary 'Flea86 level-1' product spec:

Note that I've included 'level-1' in the model name, to indicate this system is positioned as an entry-level model. Features like EGA/hi-res, faster/more powerful CPU and expansion bus types as they evolve will be marked as Flea86 level-2/3/4 or something similar to it.

Might be a little too informative for a simple brochure, but I figured there's no point in not being up-front about what one might expect from a system of this kind.

Might still need some refining, but it's a start nonetheless..

Please feel free to comment and let me know your thoughts on it. Thanks again!

Cheers Valentin

 

[Maverick1978]

I'm salivating.... especially at the prospect of being able to further overclock the CPU, and the possibility of there being other evolutions of the Flea

 

[Holmes]

When you release the 1st version, will you continue to make modifications/refinements to it? If so, can future BIOS/system changes be uploaded to this? If so, how would that be done?

 

[basman74]

When you release the 1st version, will you continue to make modifications/refinements to it?

Good Question! The micro I am using does NOT have a flash version (and I picked them 'cause they're cheap!), the firmware in these chips are therefore NOT normally updatable. While it is theoretically possible to update the emulator code while it's running in the internal RAM, the code to do this is sadly not trivial - though it IS one of the things I am working on..

Besides, for the initial 10-15 units in the event of no follow-up demand, I would prefer to release them with small 'quirks' anyway - it would give these machines some unique character ;-)

If so, can future BIOS/system changes be uploaded to this? If so, how would that be done?

If update support were to be added, it can only be done by loading a firmware update image (48K binary) on the same MMC/SD card. Update binary image would have to be at the top of the 512MB boundary of the flash drive or something i.e. not within the FAT-16 partition, since DOS won't be available inthis case..

It would be interesting to explore this avenue further to also allow emulation of other systems (C-64), but that's going way, way beyond what I originally wanted to achieve with this project in the first place - a working PC system on minimal hardware..

Regards,
Valentin

 

[Holmes]

Thanks! I'm still very interested.

 

[m1k3e]

This looks absolutely freakin' amazing. Count me in

 

[basman74]

Flea86 Project progress update - EGA/VGA finally nailed!

Flea86 Project progress update - EGA/VGA finally nailed!

Hi all,

After a few distractions (including a bout of flu), I managed to get back to seeing to what extent I can transform this minimal hardware into a real PC..

Through a good deal of pouring over the EGA (and several VGA) technical references along with some valuable assistance from the resident young-gun Mike Chambers (thanks for the unchained 256-color VGA info Mike), finally got my head around the quirky architecture that makes up the EGA and also VGA. I put together some YouTube video demos to help illustrate this point:

Flea86 demo running Windows 3.0 (640x350 EGA 16-color)
Flea86 demo running Gods (320x200 VGA 16-color)
Flea86 demo running Wolfenstein-3D (320x200 VGA 256-color)
Flea86 demo running CD-MAN (640x350 EGA 16-color)
Flea86 demo running Indianapolis 500 (320x200 EGA 16-color)


Unfortunately in terms of the current level-1 hardware, full EGA/VGA emulation will not be possible due to the system DRAM bottleneck on the Flea86 level-1 system. Also, the slightly squashed screen aspect on some of the 320x200 modes may not be everyone's cup of tea.. but hey, at least it works.. :-D


Regards,
Valentin

 

[Maverick1978]

You have me drooling here...

Curious - this is emulating an XT-class machine, correct? But if you're running Windows 3.0, you've moved beyond simple XT stats. Is the Flea86 now an AT-class system?

I'm really enjoying following your progress, Valentin...

 

[Lord Moz]

You have me drooling here...

Curious - this is emulating an XT-class machine, correct? But if you're running Windows 3.0, you've moved beyond simple XT stats. Is the Flea86 now an AT-class system?

I'm really enjoying following your progress, Valentin...

Win 3.0 will run on an XT in real mode. Win 3.1 dropped real mode, and WfW 3.11 dropped protected mode, running in "Enhanced" mode only.

WfW 3.11 loss of protected mode was mostly political as far as I could tell, as with some tinkering (borrowing an appropriate win.com from a previous 3.1 install) you can get it running on a 286 in protected mode, but the loss of real mode was really necessary as it was holding the whole platform back.

__
Trevor

 

[mdc]

This is quite possibly one of the most awesome things I've ever seen.

If you were to add flash update capability (simple hard-coded flashing handler, able to re-program the BIOS from a ROM present on the SD card, similar to the EeePC would work well), in order to provide an upgrade path without buying an entirely new unit, I daresay many people would happily spend £99 (or $149) on one of these things to have as a DOS gaming platform, myself included. If you were to add some sort of networking capability, you'd probably even have attention from the business market.

 

[basman74]

Curious - this is emulating an XT-class machine, correct? But if you're running Windows 3.0, you've moved beyond simple XT stats. Is the Flea86 now an AT-class system?

As it stands, the current Flea86 level-1 system has several enhancements over a bog standard IBM-PC/XT:

1.) Numerous 80188/86 op-codes i.e. push/shift immediate, push/pop all etc. are included
2.) Offset portion of EA no longer 'wraps around' from 0xFFFF to 0x0000 as per the 8088/86 CPU
3.) Integrated PS/2 mouse support
4.) To enable PS/2 mouse support under Windows, BIOS ROM device signature is set to 0xFC i.e. IBM-AT (or clone?)
5.) Up to 832K system RAM standard (640K+192K UMA). Unfortunately, EGA/VGA video uses the 192K as VRAM..

So in other words, it's almost a '186-based XT, masquerading as an AT (via hacked ROM signature) with some small PS/2 functionality..

 

[basman74]

Win 3.0 will run on an XT in real mode. Win 3.1 dropped real mode, and WfW 3.11 dropped protected mode, running in "Enhanced" mode only.

WfW 3.11 loss of protected mode was mostly political as far as I could tell, as with some tinkering (borrowing an appropriate win.com from a previous 3.1 install) you can get it running on a 286 in protected mode, but the loss of real mode was really necessary as it was holding the whole platform back.

__
Trevor

Correct, though I would add the comment that use of Windows 3.0's EGA/VGA 16-color desktops on a stock XT required a processor upgrade from the original 8088 to a V20..

 

[basman74]

If you were to add flash update capability (simple hard-coded flashing handler, able to re-program the BIOS from a ROM present on the SD card, similar to the EeePC would work well), in order to provide an upgrade path without buying an entirely new unit

Firmware update feature is possible though very problematic, due to quirkiness/limitations of the processor chip I am currently using for the level-1 Flea86..

I daresay many people would happily spend £99 (or $149) on one of these things to have as a DOS gaming platform, myself included.

If this is indeed the general consensus, then perhaps I should forget the idea of hand-building these things in ones-and-twos and partner-up with someone who can make this humble hobby go commercial.. Reason I say this is due to my current personal situation, which doesn't really allow me to make even a small run of say, fifty completed systems without breaking the bank.

If you were to add some sort of networking capability, you'd probably even have attention from the business market.

This was part of the idea around adding the FleaBUS port (basically an enhanced form of SPI..) - one could in theory bolt-on almost anything that they wished in this regard: Ethernet, WiFi, GPS/GSM, etc. in a manner similar to those used on the Arduino/Picaxe/Mbed etc.. Of course, another option could be to port the Flea86 code to another CPU with integrated ethernet/WiFi..

Given the capabilities of either an ARM or Atom based SBC vs the Flea86, I think that any widespread use would be strictly hobbyist-only, if at all. Of course, one can always dare to dream..

Regards,
Valentin

 

[basman74]

Flea86-level 1 project status update

Flea86-level 1 project status update

Hi all,

Just a quick update on this project. Good news is that 2D platform games like the Commander Keen series now run on the Flea86:

Not-so-good news however is that the Flea86 system ROM is now at maximum capacity, meaning feature additions/upgrades (other than perhaps some crude EGA font compatibility, if I can fit it in..) would not be possible with the level-1 hardware. Although some EGA/VGA support now exists it's still very far from complete..

In addition, I have reached some limits of what is possible with a tiny 8-bit processor, to run the PC emulation. Therefore, I will probably use a 32-bit processor host for any future 2nd-level Flea..


Regards,
Valentin