Good luck!

I wonder if it would be smarter to use an existing synthesizable open source CPU for the back end and modify the micro ops translation layer to support x86.

Will this do?

http://www.malinov.com/Home/sergeys-projects/sergey-s-xt

And there's also this:
http://www.vcfed.org/forum/showthread.php?464 … -with-real-8088

gdjacobs wrote:

I wonder if it would be smarter to use an existing synthesizable open source CPU for the back end and modify the micro ops translation layer to support x86.

OK, after doing some research that sounds like a good idea. Would it make sense to make it in one of the "Socket" form factors or simply solder it directly to the board? Maybe people would want to "upgrade" their boards with original processors. But with the FPGA you could, in theory, reprogram it to simulate pretty much any processor, right? How fast could you get with it? 386? 486? Pentium+?

stamasd wrote:

Will this do?

http://www.malinov.com/Home/sergeys-pro ... ergey-s-xt

That's kind of, sort of what I'm thinking except:
1. It's too big
2. It requires too much external stuff (video, HDD controller, sound card, ISA slot board, etc.)
3. It only uses 8088, so it's basically an XT system. I'm thinking AT with 286 or greater.

stamasd wrote:

And there's also this:
http://www.vcfed.org/forum/showthread.p ... -real-8088

That's more like it, except it's still only XT w/8088.

what your really saying is, you want dosbox in an fpga?

Not necessarily, but that would serve the purpose... I want a board that functions just like a fully carded-up typical 386/486 PC, in a small inexpensive form factor. Basically something that you could drop into, say, your average 386 system case instead of the original guts and not know the difference.

This is probably what you're looking for:

http://opencores.org/project,next186

The Xilinx Spartan board isn't particularly big, I don't think it is larger than mini-itx. A normal AT size case is likely overkill.
The bonus is you can simulate/emulate other hardware. It isn't as "pure" as using the original hardware, but it has to be better than running PC-Em on a Raspberry Pi (no offense to the PC-Em guys).

I am not sure how you'd go hooking up disk drives, but I imagine the FPGA dev board has got USB or SATA on it, or an SD card.
Problem is it will be way more $$ than a Raspberry Pi, but I think most FPGA boards that would be suitable for this would be in the $100 to $200 range.

My personal approach, if hardware were to be developed, would be to investigate solutions like the ZFx86 and have them running FreeDOS or something, license permitting of course.

http://www.zfmicro.com/pdf/WebProductBrief.pdf

Well that ZFx86 looks really cool, but that looks like something you would have to custom design a motherboard for.

You would, but they are very simple because almost everything is integrated. They use them in newly produced ISA 486 boards for replacing the ones in factories and such, but these are ridiculously expensive due to them being for that environment. In short, if a factory still uses a 486 and had some proprietary cards and production equipment, it could cost millions to replace the whole system. Thus, you can pretty much charge what you like for replacement parts to keep that system going. By contrast, I believe the ZFx86 itself is fairly low-cost.

A company called ESA make such a board and it appears like this;

Fairly simple when you consider how many features it has built-in.

My thoughts would be to produce something like that, but perhaps in a different form factor. Either a laptop type device or perhaps µATX.

These are also speed adjustable, take modern PSUs, have a whole host of interfaces (IDE, SATA, mini-PCI, and I think CF to name a few). The CPU uses less than a single Watt at 100MHz and it seems 128MB of RAM is supported, I am unsure if there is an L2 cache, I'd have to check the specs properly again.

snorg wrote:

This is probably what you're looking for:

http://opencores.org/project,next186

OK, after searching around on that site I found these two, which fit the bill even better:
http://opencores.org/project,ao486 - Most feature rich, actually has 32-bit 386 instruction set. Also has VGA and the beginnings of SB 2.0 implementation - looks very promising. Something to consider.
http://opencores.org/project,zet86 - Seems to be the most developed, but also seems to have been abandoned a few years ago. Detailed documentation on how to upload to various FPGA development boards.
Let me know if I missed one but I think those are the ones that might work.

HighTreason wrote:

My personal approach, if hardware were to be developed, would be to investigate solutions like the ZFx86 and have them running FreeDOS or something

snorg wrote:

that looks like something you would have to custom design a motherboard for.

HighTreason wrote:

You would, but they are very simple because almost everything is integrated.

The ZFx86 looks pretty cool, basically what I was originally looking for, but the idea above of having integrated VGA and SB 2.0 is tempting. With the ZF you'd have to have a separate VGA and sound card - but maybe that's a better solution.

Ideally I want one "base" board which has CPU, VGA, sound card, ISA controllers... then you would have "extension" boards like ISA slots, etc.

And for PSU I was hoping it could be a solid-state thing, with one 12V input to the "base" board.

keenmaster486 wrote:

snorg wrote:

Ideally I want one "base" board which has CPU, VGA, sound card, ISA controllers... then you would have "extension" boards like ISA slots, etc.

🤣 so.. a motherboard then? 🤣 basically an embedded motherboard. amd geode, or pc104 or stuff like a picmg board.

its like you suddenly did a 180 from your original post.

@keenmaster486; VGA I'm not sure about, the ESA boards use a Silicon Graphics solution which appears to be single chip, though I am sure there are probably a bunch of NOS S3 and Cirrus chips left out there somewhere too. I think ATi kept making PCI chips until quite late on and there are probably a few SiS chips left out there too though those wouldn't be as fast.

Audio would he the harder one to source, you'd either have to butcher a bunch of Sound Blasters or settle for something like a single-chip Crystal solution. If it were me, I'd just leave a slot and have the card be up to the user, but if you want it integrated and especially if you want a simple power supply, more research would probably be needed. I suppose if you can emulate a CPU with one of these BGAs (This kind of stuff is new to me, so forgive me if I'm being ignorant) that you might be able to actually implement a Sound Blaster compatible audio solution and joyport that way, but I have no idea if anybody has ever done this or how difficult it might be in practice.

Of course the big negative here is that if you have to dip into old parts like Crystal chips and S3 Trios, they generally aren't made anymore and may be hard to source reliably. It's a shame the STPC is no longer produced as that had onboard VGA (I own one of these from an DFI-ITOX Tiger Star system) and had a Cyrix core - ST's license to produce the Cx486 lasted until at lest 2009 and they made heavy use of it, it's pretty weird running a 486 with ATX power and thermal monitoring. I am unsure if the 133MHz version used the same core. I suppose you might still be able to source them somewhere, but that would still leave audio.

The BGA solution has potential too and it would be interesting to see how that would work out as well. I just know very little about doing things this way, my knowledge does not extend far past through-hole parts and 74 logic, I can usually get stuff to work to some extent with heavy reliance on datasheets but I make a lot of blunders and usually fry at least three prototypes of anything I try to glue together. But, yeah, I'm just throwing ideas around, it will be interesting to see where this idea ends up.

BloodyCactus wrote:

so.. a motherboard then? basically an embedded motherboard. amd geode, or pc104 or stuff like a picmg board.

Kind of, yeah. But a small, inexpensive, verison of that, and specifically designed for maximum DOS compatibility.

BloodyCactus wrote:

its like you suddenly did a 180 from your original post.

Not really. See here:

keenmaster486 wrote:

Maybe just a motherboard with basics: CPU slot, port pinouts, ISA slots, etc. Or maybe it could be the x86/retro version of the Raspberry Pi. It might conform to already existing standards such as Socket 7 or Socket 3 or 5.

But I have evolved my original idea somewhat after having researched the FPGA solution which allows CPU, VGA, and sound in the same chip.

HighTreason wrote:

@keenmaster486; VGA I'm not sure about, the ESA boards use a Silicon Graphics solution which appears to be single chip, though I am sure there are probably a bunch of NOS S3 and Cirrus chips left out there somewhere too. I think ATi kept making PCI chips until quite late on and there are probably a few SiS chips left out there too though those wouldn't be as fast.

Audio would he the harder one to source, you'd either have to butcher a bunch of Sound Blasters or settle for something like a single-chip Crystal solution. If it were me, I'd just leave a slot and have the card be up to the user, but if you want it integrated and especially if you want a simple power supply, more research would probably be needed. I suppose if you can emulate a CPU with one of these BGAs (This kind of stuff is new to me, so forgive me if I'm being ignorant) that you might be able to actually implement a Sound Blaster compatible audio solution and joyport that way, but I have no idea if anybody has ever done this or how difficult it might be in practice.

That actually has been done, here:

keenmaster486 wrote:

OK, after searching around on that site I found these two, which fit the bill even better:
http://opencores.org/project,ao486 - Most feature rich, actually has 32-bit 386 instruction set. Also has VGA and the beginnings of SB 2.0 implementation - looks very promising. Something to consider.

Has SB 2.0, except without OPL2 I think. This would be a great solution if it could be made to work: A single chip has the CPU, VGA, and basic sound implementation (in this case, SB 2.0). But you could have an extension board for the base board with some ISA slots on it, for other sound cards.

I really like the idea of an open-source DOS gaming laptop created from this idea. If you had the base board you could sell that separately, and also sell a kit with the board, screen, case, etc... "Build your own Retro Gaming PC/Laptop" or something.

EDIT: Don't worry about ignorance... you know way more about this than I do. I'm learning on the fly but I still really want to get a project like this off the ground, or at least help it 😁

http://www.aliexpress.com/item/ES1688F-MQF100 … 0408.3.1.mYR4PM those chips could be used for audio I suppose (ESS 1688F - looks like they are available in high quantities).
Implementation doesn't need too much space: http://computer-retro.de/Bilder/Soundkarten/K … -Soundkarte.jpg

keenmaster486 wrote:

Kind of, yeah. But a small, inexpensive, verison of that, and specifically designed for maximum DOS compatibility.

Inexpensiveness doesn't come by the design, but your ability to produce and selling it in high volumes. Niche products will be intrinsically expensive than a mass produced retail product because them are produced and sell in small quantities, and it just goes higher when you involve things like multilayer PCBs and BGA parts, because you need equipment to assemble them, or make an contract with a chinese fab to produce your boards. Profitable only comes wen you produce at least 10,000 units and expect to sell all them.

Just check Amiga motherboard market.

Design plays a big part in cost by both creating a solution optimized for price and providing feedback or control of project scope (simple is cheaper). Of course, high volume production allows you to spread fixed costs over more units and also bargain more aggressively or use price breaks with material vendors.

Low budget production could be achived only by using available FPGA chips or embedding emulation software into ARM computers etc, + making cases of laser-cut acrylic, HIPS or something like this with additional 3D printer parts. Cheap 3D printers are being assembled in this way, this isn't a big market so you don't need mass production, but there are some limitations involved and you can't make a case of any shape you want because you can't injection mold plastic, so everything has to be straight, no fancy shapes. It is not possible to 3D print entire PC case (unless it's very small) because it would take weeks.

Here is Armiga - similar project. http://www.armigaproject.com/
It has 3D printed case, but it is only a bit larger than floppy drive.

that's why I'd go with the PC route, because then you can rely on existing cases by going with a µAtX or ITX form factor. You wouldn't have to develop a case and you could use the crappiest case and crappiest power supplies because the current draw and thermal requirements would be so low.

Tempted to look at my board design software and see if I can bodge it into working with PGAs and more than two layers. Unfortunately, I have too many unfinished projects to start really screwing around with something like that.