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Project SBC-386EX [message #3771] Fri, 17 November 2017 13:11 Go to next message
jcoffman is currently offline  jcoffman
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To All:

A new project to go beyond the SBC-188 has been launched. The goal is an embedded 386-level CPU (& peripheral) board. The 80C188 was an early Intel high-integration processor, as is the i386-EX, with lots of goodies on a single chip.

Project is at https://www.retrobrewcomputers.org/doku.php?id=boards:sbc:sb c-386ex

--John
Re: Project SBC-386EX [message #3772 is a reply to message #3771] Fri, 17 November 2017 16:16 Go to previous messageGo to next message
Wayne W is currently offline  Wayne W
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This looks awesome John. I would be happy to participate in initial build and test, if you think it makes sense. I have done a fair amount of millipede soldering with 100% success, so I can probably handle it.

-Wayne
Re: Project SBC-386EX [message #3774 is a reply to message #3772] Sat, 18 November 2017 08:17 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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Wayne,

Good to hear from you. The present board is a throw-away, but I want to become more comfortable in dealing with such a complicated chip. As such, I have only 4 boards, but plenty of adapters. Let me do some preliminary tests today to make sure the board is not a total disaster, then I can ship you a bundle with a couple of adapters.

Any final design is months away. This is a stepping-stone.

--John
Re: Project SBC-386EX [message #3775 is a reply to message #3774] Sat, 18 November 2017 08:37 Go to previous messageGo to next message
danwerner is currently offline  danwerner
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Hey John, also happy to help -- just let me know when/if you are ready for testers.

Dan

Re: Project SBC-386EX [message #4060 is a reply to message #3775] Tue, 09 January 2018 21:33 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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Update: Wayne, Dan, and I have prototype boards running with FPU's. A chip update was needed to get the 33Mhz Cyrix FPU to handle the READY# line fast enough.

TBD: final board to be VME size (aka 6U) or RetroBrew standard (3U). 6U could have all the goodies, but 3U may be a better choice.

Goodie: Pro: Con:

64Mb DRAM mandatory --
COM1 mandatory (on CPU) --
RTC & NVRAM mandatory (DS1302)
SRAM (32K) use for debugging space, DIP28
IDE w/ DMA (2)CF card I/O connector space
FPU cool space, PLCC68
FDC w/ DMA easy MSDOS install space, PLCC44+connector
SD socket very useful space, space, space
COM2+ParPort PC/AT compat space, PLCC68
VGA & kbd PC/AT compat none, it is a separate board option

The FDC and SD socket are probably impossible on a 3U board.
The FPU, cool, but not needed. SBC-188 did ok with emulator only.
COM2 comes almost for free if SD socket & (FPU or FDC) are eliminated due to shared I/O pins on the 386EX chip.
COM2 would be TL16L552 chip: COM2,COM3 & ParPort

--John
  • Attachment: 386EX-2.txt
    (Size: 1.19KB, Downloaded 102 times)

[Updated on: Tue, 09 January 2018 21:36]

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Re: Project SBC-386EX [message #4061 is a reply to message #4060] Tue, 09 January 2018 21:37 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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Formatting is lost in the post. Download the TXT file to see formatted columns.
Re: Project SBC-386EX [message #4062 is a reply to message #4060] Tue, 09 January 2018 21:38 Go to previous messageGo to next message
ab0tj is currently offline  ab0tj
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How about a micro-SD socket? I used one on my 186EB SBC and it was not nearly as hard to solder as I expected.
Re: Project SBC-386EX [message #4063 is a reply to message #3771] Wed, 10 January 2018 06:48 Go to previous messageGo to next message
danwerner is currently offline  danwerner
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The 3U form factor is easier to work with, but we have done the 6U form factor before (the 6x0x) and the community seemed to accept it just fine. There were some advantages to having ATX mounting holes in the board and an ATX power connector so that it could be mounted in an ATX case if desired. The only recommendation that I would make is to request that we make it easier to plug in an ECB card into the board when mounted in an ATX case -- while this is possible with the 6x0x, (in some cases) it is not always straight forward.

Dan
Re: Project SBC-386EX [message #4064 is a reply to message #4062] Wed, 10 January 2018 07:38 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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The biggest board real-estate hog on this project is the 50x50mm 386EX Adapter board, which would save PQFP surface-mount soldering. There is a socket for the 386EX chip, but it is so ridiculously expensive (and tricky to use), that I abandoned this idea.

The micro-SD socket is an idea worth looking into. Thank you for this suggestion.

--John


Re: Project SBC-386EX [message #4065 is a reply to message #4064] Wed, 10 January 2018 12:43 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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The micro-SD sockets from Molex are as small as 5x11.5mm meaning socket size is no issue. A little more space is needed for the resistor divider networks, but micro-SD is looking possible at this moment.

--John
Re: Project SBC-386EX [message #4066 is a reply to message #3771] Wed, 10 January 2018 15:44 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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Excited about this. I'd be ok with QFP soldering, I've done it before. But I can see why not everyone would be. However, it is super easy once you have a hot air rig. So if I'm reading this right, MS-DOS is definitely on the horizon.

Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: Project SBC-386EX [message #4068 is a reply to message #4066] Wed, 10 January 2018 17:34 Go to previous messageGo to next message
Andrew B is currently offline  Andrew B
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NetBSD might run on this as well (I have has success booting a kernel on a 486 with 40MB of RAM)
Re: Project SBC-386EX [message #4071 is a reply to message #4068] Wed, 10 January 2018 21:08 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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In discovering the 386EX, I was very pleased to see the addition of 2 more address lines over the 386SX's 24. A single 64Mb SIMM ($10-12) will fill the memory needs for a good OS.

Andrew, I solicit your (and others'Wink s/w expertise when we have a 64Mb board up.

=========================================================

The PQFP is really easy to solder. I was pointed in the direction of using a dry chisel tip iron, and NO additional solder, but to depend on the board HASL layer. I've practiced on adapter boards with tinned pads, and HASL only pads. The latter are easier with only the Hot Air Solder Layer.

--John
Re: Project SBC-386EX [message #4076 is a reply to message #4071] Thu, 11 January 2018 07:11 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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The fact that it is more of a MCU than a uP helps I'm sure. I noticed it has several internal Serial ports, counter/timers, etc. it's a really interesting device.

Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: Project SBC-386EX [message #4079 is a reply to message #4076] Thu, 11 January 2018 11:06 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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jdgabbard wrote on Thu, 11 January 2018 07:11
The fact that it is more of a MCU than a uP helps I'm sure. I noticed it has several internal Serial ports, counter/timers, etc. it's a really interesting device.


Yes, it is pretty much a PC/AT with a 386SX CPU on an integrated chip.

Re: Project SBC-386EX [message #5639 is a reply to message #4079] Thu, 29 November 2018 08:28 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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John, Have you made any further progress on this? It doesn't appear there has been any activity on the Wiki, and I haven't seen you post anything further on this. Have you given up on this project?

Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: Project SBC-386EX [message #5641 is a reply to message #5639] Thu, 29 November 2018 10:08 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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The SBC-386EX 2.0 is now a real computer: UART, FPU, 32K SRAM, 64MB DRAM, IDE connector, DS1302 RTD/NVRAM, RetroBrew ECB bus. The microSD interface has not been tested.

However, the ROM will not run MSDOS, PCDOS, or FreeDos. After many months, I have completely burned out on this ROM situation.

Get my e-mail address from the Board Inventory, and contact me off of the Forum if you have any inclination to attack this project.

Dan provided the best photo of the completed board. (see attached)

--JohnC
Re: Project SBC-386EX [message #5642 is a reply to message #5641] Thu, 29 November 2018 11:58 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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I sent you an email.

Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: Project SBC-386EX [message #5677 is a reply to message #5642] Mon, 03 December 2018 01:44 Go to previous messageGo to next message
b1ackmai1er is currently offline  b1ackmai1er
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Hi John,

Looks Terrific. Without a MSDOS this could still theoretically run linux right?

Are the Lattice GALS replacable by other manufacturers parts?

If anyone is interested, I have ordered some boards.

Regards Phil
Re: Project SBC-386EX [message #5678 is a reply to message #5677] Mon, 03 December 2018 08:21 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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Both Linux & Coherent should be runnable.

The GALs are 16V8's so that Lattice or Atmel parts may be used.

--John
Re: Project SBC-386EX [message #5690 is a reply to message #5678] Wed, 05 December 2018 15:03 Go to previous messageGo to next message
etchedpixels is currently offline  etchedpixels
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Linux dropped 386 support some time ago both kernel and user space. In theory 3.7 is the last kernel that supports it. In practice all the 386 support got really dodgy well before that.

Old old Linux should work (1.2.13LMP is still probably the best ever Linux for a 386 Cool Wink

It would certainly be interesting to see if it did run Linux because Linux except for the bootstrap has very minimal firmware dependancies so it might help identify if it's a hardware problem, an errata issue (the 386EX has a few corkers) or firmware. Ditto Minix.

Re: Project SBC-386EX [message #5705 is a reply to message #5690] Thu, 06 December 2018 17:07 Go to previous messageGo to next message
ABurrows is currently offline  ABurrows
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i would be very keen to work on a linux OS for this board.
Re: Project SBC-386EX [message #5731 is a reply to message #5705] Wed, 12 December 2018 00:40 Go to previous messageGo to next message
ABurrows is currently offline  ABurrows
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would anyone be able to tell me where i can get the KiCAD libraries for this project:

00N8VEM
01RetroBrew
SBC-188

thanks!

edit: have emailed you John C

[Updated on: Wed, 12 December 2018 00:51]

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Re: Project SBC-386EX [message #5734 is a reply to message #5731] Wed, 12 December 2018 07:44 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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The schematic libraries have been posted to Google Drive:

https://drive.google.com/file/d/1w233I00AsBffZ1XTjqN5guZGbf9 MgRPk/view?usp=sharing

These libraries have components which correct Kicad (old) library errors, and new components that are needed for several of my projects.

--John C. (see "board inventory" if you need to contact me directly.Wink
Re: Project SBC-386EX [message #5735 is a reply to message #5734] Wed, 12 December 2018 18:19 Go to previous messageGo to next message
ABurrows is currently offline  ABurrows
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Thnaks John,

will this board (provided adapter board or direct) work with:

Cyrix FasMath 387 CX-83D87-25-GP --> 68 Pin
Cyrix 87DLC-40QP --> 68 Pin

i.e. is there a clear difference between the FPUs that work with the "DX" and "SX" "EX" 80386 variants

edit: i think i remember here.. the 387DX will work with the standard 80386 (DX), and the 387SX will work with the 80386SX and EX variants.. re 16 bit bus width.. if im not mistaken.

[Updated on: Wed, 12 December 2018 19:19]

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Re: Project SBC-386EX [message #5736 is a reply to message #5735] Wed, 12 December 2018 21:48 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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The 80386EX CPU is based on the 80386SX processor + 2 extra address bits + OEM peripherals.
It works with FPU's that work with the 386SX (16-bit data bus). It does not work
with the FPU's you mention. Try FPU's ...

Intel N80387SX-33 or -25
Cyrix CX83S87-33
others for the SX
Re: Project SBC-386EX [message #5738 is a reply to message #5736] Thu, 13 December 2018 01:40 Go to previous messageGo to next message
ABurrows is currently offline  ABurrows
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Thanks John!
Re: Project SBC-386EX [message #5804 is a reply to message #3771] Thu, 27 December 2018 03:32 Go to previous messageGo to next message
trick-1 is currently offline  trick-1
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Hi Folks

Anyone have a spare adapter board for the 386EX?

Richard
Re: Project SBC-386EX [message #5809 is a reply to message #5804] Thu, 27 December 2018 13:12 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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There are two adapter boards for the 80386EX CPU:

1. 65mm x 65mm -- used on the prototype board, but now only good for soldering practice. I have a couple of these and will send them for the cost of postage.

2. 50mm x 50mm -- used on the production (2.0) board, if desired. I'm trying to make this board publicly available at PCBway as a shared project. As long as I have the last few on hand, I am including one with each ECB/SBC order.

Contact me through the e-mail link at the bottom of the Board Inventory page. [John Coffman]
Re: Project SBC-386EX [message #6443 is a reply to message #3771] Mon, 12 August 2019 23:58 Go to previous messageGo to next message
trick-1 is currently offline  trick-1
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Hi There,

I am yet to build up my board, waiting for the CPU to arrive from ebay.

I noted the comments about DOS not working as desired.

I found the following https://www.taskit.de/downloads.html which has something called MoDOS that, from what I can tell, is designed to run on a 386EX....not sure if it will work but if anyone has a card built and was willing to give it a try would be interested to know if it works.....

Cheers

Richard
Re: Project SBC-386EX [message #6444 is a reply to message #6443] Tue, 13 August 2019 09:13 Go to previous messageGo to next message
jcoffman is currently offline  jcoffman
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The s/w is from a firm that is selling hardware, so there may be licensing constraints; but DOS does run on the 386EX, just not on the RetroBrew board BIOS.

====================

During the SBC-188 project, Sergey noted that MSDOS mucks with lots of devices in the range 000h..3FFh. Since this range conflicts with some of the board peripherals if the Peripheral Registers are set to 000h, all on-board peripherals had to be mapped to the range 400h..5FFh. Then MSDOS did not crash the board.

Hence, since the PC addresses of peripherals on the 386EX board cannot be mapped out of the reach of MSDOS, I expect some peripheral(s) is/are getting scrambled.

--John

Re: Project SBC-386EX [message #6448 is a reply to message #6444] Wed, 14 August 2019 16:32 Go to previous message
etchedpixels is currently offline  etchedpixels
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Did you try booting a very old DOS (eg 2.x) from back when DOS actually stuck to the BIOS a bit better ?

The 386EX peripherals are mappable in AT compatible way and the low ports for chip config (0x21 etc) shouldn't be touched by anyone even DOS. FreeDOS might also be helpful because you have source code.

Alan

[Updated on: Wed, 14 August 2019 16:33]

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