LewisRaz wrote on 2020-03-12, 20:45:

Nitroraptor53 wrote on 2020-03-08, 16:19:

https://i.ebayimg.com/images/g/ZtEAAOSwAKxWU3g2/s-l1600.jpg could this board be tweaked with an onboard CPU, remove to EISA slots, and a few other tweaks?

I have 2 of those exact boards and the CPU comes on a seperate board that is again half the size of that motherboard, which is already huge.

Would that board fit in an MATX case?

IBM valuepoints, PS/1 and like based on 486 and pentium started using soft power power supply that is pre-ATX design but works exactly like one.
So that is matter of figuring out how this soft power works.

Cheers,

ISA would suffice, it has enough bandwith for all VGA Stuff.

Maybe it would be better to use 2 FPGAs then, one with AO486 and one with Bus Interface and I/O.

The AO486 Speed depends on FPGA used, Clock Speed, etc..
There is also ZET CPU but i think its only 80186.

Nitroraptor53 wrote on 2020-03-13, 22:29:

LewisRaz wrote on 2020-03-12, 20:45:

Nitroraptor53 wrote on 2020-03-08, 16:19:

https://i.ebayimg.com/images/g/ZtEAAOSwAKxWU3g2/s-l1600.jpg could this board be tweaked with an onboard CPU, remove to EISA slots, and a few other tweaks?

I have 2 of those exact boards and the CPU comes on a seperate board that is again half the size of that motherboard, which is already huge.

Would that board fit in an MATX case?

Not a chance. A rough guess is that it has more surface area than 2 mATX boards

It's a nice idea to use AO486, but I'd really like to help all the people who want an mATX 486 board with a REAL 486 CPU.

matze79 wrote on 2020-03-13, 22:40:

ISA would suffice, it has enough bandwidth for all VGA Stuff.

Ug. Doesn't the fastest ISA card only get something like 18fps in Doom? I know that was some peoples experience but I know that I would want more.

BinaryDemon wrote on 2020-03-15, 03:35:

matze79 wrote on 2020-03-13, 22:40:

ISA would suffice, it has enough bandwidth for all VGA Stuff.

Ug. Doesn't the fastest ISA card only get something like 18fps in Doom? I know that was some peoples experience but I know that I would want more.

21 FPS with my 2MB card!

Some time ago I have made a couple of related things:

http://www.vcfed.org/forum/showthread.php?464 … 9572#post379572
http://www.vcfed.org/forum/showthread.php?464 … 6939#post426939

With 486GX I managed to run MS DOS, then started designing 486 motherboard similar to my FPGA XT board. Still used 486GX - didn't have 3.3V 486 CPUs handy and didn't want to bother with level shifters.
Ordered a first version of the PCB but never assembled it - one more time lost interest in electronics... Now with restricted travel thinking about restarting the project...

Perhaps an interesting angle on the FPGA front. I took a better look at my smallest 486 board today - a Digital Logic MSM586SEG It's PC/104 board, so 90x96mm.

Why is this interesting? It's based around the AMD Elan 520, so basically an Am5x86 with build-in SDRAM memory controller and PCI bridge, together with UARTs and PC/AT Compatibility Logic, i.e. ISA bridge.

Not perhaps as nice as a 'real' So3, but it's real 486 hardware coupled with exactly the bits that would prove challenging to implement in FPGA. The board has various other chips- an SMSC FDC37B787 multi-I/O chip, an ATi Rage Mobility M1 with 8MB RAM, an OPTi Firelink 82C861, an Intel 82551 NIC, an EEPROM - and a big Xilinx CPLD, XC95144XL. Not entirely sure what it's doing as all the major functions seem covered by the other chips...

This is the device: ftp://aplica.at/Manuals/DigitalLogic/English/ … M586SEG-SEL.pdf

Potentially this could fill in the gaps between pie-in-the-sky dreaming and having a concrete concept that is executable and proven. All you'd sacrifice would be the real CPU socket. All the other stuff could be connected to either ISA or PCI buses.

AMD Elans can still be bought new. There's an ad on eBay for 100 pieces SC520 for USD 935.54 (or best offer...), so that's USD 9.36 per unit - i.e. very affordable for a project like this.

I have one of the Elan520 based PC104 boards, and the main problem is lack of cache which hurts performance a lot. PCI bus will allow all other things to be taken care of though.

dionb wrote on 2020-03-22, 16:23:

Perhaps an interesting angle on the FPGA front. I took a better look at my smallest 486 board today - a Digital Logic MSM586SEG […]
Show full quote

Perhaps an interesting angle on the FPGA front. I took a better look at my smallest 486 board today - a Digital Logic MSM586SEG It's PC/104 board, so 90x96mm.

Why is this interesting? It's based around the AMD Elan 520, so basically an Am5x86 with build-in SDRAM memory controller and PCI bridge, together with UARTs and PC/AT Compatibility Logic, i.e. ISA bridge.

Not perhaps as nice as a 'real' So3, but it's real 486 hardware coupled with exactly the bits that would prove challenging to implement in FPGA. The board has various other chips- an SMSC FDC37B787 multi-I/O chip, an ATi Rage Mobility M1 with 8MB RAM, an OPTi Firelink 82C861, an Intel 82551 NIC, an EEPROM - and a big Xilinx CPLD, XC95144XL. Not entirely sure what it's doing as all the major functions seem covered by the other chips...

This is the device: ftp://aplica.at/Manuals/DigitalLogic/English/ … M586SEG-SEL.pdf

Potentially this could fill in the gaps between pie-in-the-sky dreaming and having a concrete concept that is executable and proven. All you'd sacrifice would be the real CPU socket. All the other stuff could be connected to either ISA or PCI buses.

AMD Elans can still be bought new. There's an ad on eBay for 100 pieces SC520 for USD 935.54 (or best offer...), so that's USD 9.36 per unit - i.e. very affordable for a project like this.

Just a very small comment, as I don't really want to particpate in this thread 😁:

The initial posting was about having a test platform for 486-cpus, because many people still have some cpus, but no mainboards.
So an AMD Elan board makes zero sense for that.

CoffeeOne wrote on 2020-03-22, 19:47:

[...] […]
Show full quote

[...]

Just a very small comment, as I don't really want to particpate in this thread 😁:

The initial posting was about having a test platform for 486-cpus, because many people still have some cpus, but no mainboards.
So an AMD Elan board makes zero sense for that.

The original post was for a board with every possible bus, video option and the kitchen sink thrown in - and that on uATX form factor and assumedly at a price point someone might want it. In itself it made zero sense already. My suggestion explicitly cuts the socket out to gain feasibility, as no one had actually posted anything feasible yet. Perfect match? Nope. Didn't pretend it was.

dionb wrote on 2020-03-22, 22:22:

CoffeeOne wrote on 2020-03-22, 19:47:

[...] […]
Show full quote

[...]

Just a very small comment, as I don't really want to particpate in this thread 😁:

The initial posting was about having a test platform for 486-cpus, because many people still have some cpus, but no mainboards.
So an AMD Elan board makes zero sense for that.

The original post was for a board with every possible bus, video option and the kitchen sink thrown in - and that on uATX form factor and assumedly at a price point someone might want it. In itself it made zero sense already. My suggestion explicitly cuts the socket out to gain feasibility, as no one had actually posted anything feasible yet. Perfect match? Nope. Didn't pretend it was.

I fully agree that the whole thread makes little sense.
I was referring to the very first sentence:

3/4/2020: Hi guys! I was wondering - how many people have a loose 486, 5x86, or Pentium Overdrive Chip and no spare motherboards?

Nitroraptor53 wrote on 2020-03-15, 15:58:

BinaryDemon wrote on 2020-03-15, 03:35:

matze79 wrote on 2020-03-13, 22:40:

ISA would suffice, it has enough bandwidth for all VGA Stuff.

Ug. Doesn't the fastest ISA card only get something like 18fps in Doom? I know that was some peoples experience but I know that I would want more.

21 FPS with my 2MB card!

Stick it inside a 233Mhz MMX and watch FPS Fly.

its just a matter of how fast the DATA can be written to the VGA RAM. For 320x200/240 bandwith is enough.

https://hackaday.com/2015/11/17/a-modern-386- … elopment-board/

Maybe this is intressenting too 😀

Hello Vogons / Everybody - this seems to be my first post here and it is about to be a long one...

So for some time I have also been considering building a motherboard for sticking 486-class CPUs into it. My approach would make it expensive but this kind of project is doomed to be against the economy and reason anyways.

My design considerations:

1. Target format: Mini-ITX - I want a nice small portable PC, I want to use standard cases and power supplies
2. I want to allow experimenting with multiple ISA and PCI cards. Maybe overclock a good 486 CPU and beat the fastest 486-class system of all times. 😀 I would also like to integrate my 320x200->1920x1200 aspect-correction scaller and HDMI video output (VGA monitors with analog input also seem to be on the path to extinction).
3. Lengthy prototyping and designing everything from scratch to make it cheaper to manufacture in large quantities doesn't seem to make any sense to me. And this project must be rewarding - so months of PCB design just to get started are out of the question.
4. I would also like to be able to build some more units in the foreseeable future for people who would really want them - that rules out a one-time hack run. It has to be repeatable.

The only viable way I see is to extend the MiSTer by replacing the under-performing ao486 with a real CPU and add bus interfaces. Quite a lot of pins are needed to connect one so DE10-Nano won't make it in terms of hardware. The simplest way would be to port MiSTer to different hardware with a simillar/same FPGA. Enclustra Mercury+ SA2 Altera® Cyclone® V SoC Module + a Baseboard with FMC connectors seems to be the best choice I can think of: 234 available FPGA IO pins. The baseboard is lacking video output so for starters an FMC card with a HDMI serializer will be needed. Maybe something more. Port MiSTer to this new hardware. That would be Stage I.

Designing a custom FMC card with a CPU / CPU socket and optionally a SDRAM/SDRAM module socket (all 3.3V-only) and maybe some-other-stuff to make it fully MiSTer-compatible would make Stage II. Add anything you can think of: PCI/ISA sockets, voltage converters (maybe 5V-tolerant CPLDs as voltage converters) for Stage IIa. Fix and repeat. Stage IIb.

If everything more or less worked out - it's time do design a motherboard housing the SoC module and the CPU (and memory or whatever). I would go for Mini-ITX format with an additional PISA-style edge connector. So - if you want to have a big system with external PCI/ISA cards all you need to do is buy an industrial PISA backplane (and housing or build custom housing or whatever you like). These are still available cheap and new - like IEI IP-10S-RS-R40 if you want to go wild. That would be Stage III. The PISA physical socket is actually an EISA socket with different pin arrangement (ISA part is true ISA, additional pins are PCI so ISA backplanes work with PISA CPU cards). For EISA or VLB people maybe one could design a custom PISA to VLB or EISA backplane - perhaps this would be possible with rearranging the FPGA configuration.

The PISA connector could be used to extend the system if to be used with different architectures in mind. If we were to include all the hardware stuff MiSTer community desires - maybe a "486" board would reach audience beyond PC fans.

I know this makes little sense anyway, but I would forego the use of onboard or integrated VGA if only because few people would probably use it and because this would help simplify the design.
If I had endless resources, I'd probably go for a full ATX ISA+PCI (and maybe VLB) with 72p SIMM sockets and the basic stuff integrated like IDE, FDD and serial and parallel ports. I wouldn't even attempt USB.
I'd go full ATX as to create a larger amount of useable slots. If I'd go nuts I could even opt (remember this is with endless resources 😜 ) to make the first PCI slot into an AGP slot physically, just to be able to use some of the first gen AGP cards (so basically just an AGP slot that is electrically a PCI slot).
I'd also want to include a real socket and at the least add support for 3.3v chips.

It's a shame I don't have endless resources though, but at least I can dream 😜

I don't even need the ATX form factor to be honest, BabyAT motherboard that does not need -5V from the PSU to generate it, that also has an ATX connector and front panel headers would be perfect for me.

its just a matter of how fast the DATA can be written to the VGA RAM. For 320x200/240 bandwith is enough.

On stock ISA speed, you can't jump higher than 35 fps in Quake or Build engine games. Doom is even worse, due to how engine renders the frame. ISA speed is unacceptable for 486.

Obviously it doesn't answer the question directly but don't forget about the ESA industrial 486 motherboards that are still being made today (I have one), and the ZFx86 PC-on-a-chip that it uses.
The ESA board is not MicroATX, but Baby AT with an ATX power connector. Still, one could design an ATX motherboard around the ZFx86. This wouldn't let you do anything with old socketed CPUs of course, but it bypasses the issue of trying to chase down all the chipset components that haven't been made in years. The ZFx86 is based on a Cyrix 486DX4.