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Inboard 386/PC 2mb expansion CLONE

Hi Guys, this looks very interesting I’ve just picked up an Intel 386/PC cards and wondered if there are any of these blank boards available to buy? Be amazing to get it upgraded, Thanks Gareth
 
woodhog said:
Hi Guys, this looks very interesting I’ve just picked up an Intel 386/PC cards and wondered if there are any of these blank boards available to buy? Be amazing to get it upgraded, Thanks Gareth
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Be nice to know where you found your card, I still have my dead one I would very much love to resurrect…
 
Its nice to see that my initial research which i handed over to Harrison, who finalized the 2Mb version, did come in handy.
By putting our heads together we were then able to get the 4Mb running (with a small mod to the 2Mb design).
The work was just too much a hassle for me and since Harrison took over to finalize and redesign the expansion, i have no more interest in doing a new design.

More than 4mb will require a modification to the PAL-chips since the decoding is realized in there.
Only 2 banks with 1Mb or a single bank with 4mb are supported.

Replacing the PAL-chip(s) would also allow to ignore the slow 1Mb of memory on the inboard and 'move' it to the expansion card.
This would possibly open up some overclocking capabilities but i am currently disinterested in the Inboard 386 and IBM PCs.

Maybe i could make a GitHub account and add all the info i have on the inboard?! ... maybe later ;-)

-Jonas
 
stynx said:
Its nice to see that my initial research which i handed over to Harrison, who finalized the 2Mb version, did come in handy.
By putting our heads together we were then able to get the 4Mb running (with a small mod to the 2Mb design).
The work was just too much a hassle for me and since Harrison took over to finalize and redesign the expansion, i have no more interest in doing a new design.

More than 4mb will require a modification to the PAL-chips since the decoding is realized in there.
Only 2 banks with 1Mb or a single bank with 4mb are supported.

Replacing the PAL-chip(s) would also allow to ignore the slow 1Mb of memory on the inboard and 'move' it to the expansion card.
This would possibly open up some overclocking capabilities but i am currently disinterested in the Inboard 386 and IBM PCs.

Maybe i could make a GitHub account and add all the info i have on the inboard?! ... maybe later ;-)

-Jonas
Click to expand...
That sounds like a brilliant idea, but being honest I’m quite capable of soldering a board and being a tester but as far as design work goes it’s way over my head. So I will sit with fingers crossed that one of you clever people takes this on.
 
stynx said:
Its nice to see that my initial research which i handed over to Harrison, who finalized the 2Mb version, did come in handy.
By putting our heads together we were then able to get the 4Mb running (with a small mod to the 2Mb design).
The work was just too much a hassle for me and since Harrison took over to finalize and redesign the expansion, i have no more interest in doing a new design.

More than 4mb will require a modification to the PAL-chips since the decoding is realized in there.
Only 2 banks with 1Mb or a single bank with 4mb are supported.

Replacing the PAL-chip(s) would also allow to ignore the slow 1Mb of memory on the inboard and 'move' it to the expansion card.
This would possibly open up some overclocking capabilities but i am currently disinterested in the Inboard 386 and IBM PCs.

Maybe i could make a GitHub account and add all the info i have on the inboard?! ... maybe later ;-)

-Jonas
Click to expand...

I've been working on a RevC and a set of instructions for assembly, though life got in the way and had to put the project aside. I need to finish the design and order a test board!

I have the parts to do a 40mhz mod but I'm afraid that it may push the chips of the inboard too hard as they already get hot.. Someone else's stopped working after the overclock so I'm weary to do mine. The Cyrix 486 upgrade chip does make a big difference and WFW 3.11 seems to fly compared to 3.1.. Maybe because it's got more of it written/compiled for 32-bit CPUs..


Screenshot 2023-07-11 224600.png
 
harrison.frazier said:
I've been working on a RevC and a set of instructions for assembly, though life got in the way and had to put the project aside. I need to finish the design and order a test board!

I have the parts to do a 40mhz mod but I'm afraid that it may push the chips of the inboard too hard as they already get hot.. Someone else's stopped working after the overclock so I'm weary to do mine. The Cyrix 486 upgrade chip does make a big difference and WFW 3.11 seems to fly compared to 3.1.. Maybe because it's got more of it written/compiled for 32-bit CPUs..


View attachment 1260674
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Looks fantastic and far more done than I hoped, please put me on the list for when you’re ready to release it. Many thanks Gareth
 
harrison.frazier said:
@peterfleeman @sbenting @cb88
All, sorry for not seeing these sooner. I put the project on hold when I moved last year and haven't worked on it recently. I have ordered 5 more prototype boards, DM me if you want one.

Here's the BOM for this current revision:

4x dual-simm sockets (will need to snip off plastic pins on bottom to fit proto board) found here:
www.ebay.com

STRAIGHT SIMM DIMM SOCKET DUAL ROW 60 PIN 30 +30 CONTACTS - LOT OF 2 CONNECTORS | eBay

Find many great new & used options and get the best deals for STRAIGHT SIMM DIMM SOCKET DUAL ROW 60 PIN 30 +30 CONTACTS - LOT OF 2 CONNECTORS at the best online prices at eBay! Free shipping for many products!
www.ebay.com

2x 74F02N Quad 2 Input NOR Gate
2x 74F32N Quad 2 Input OR Gate
8x 512K 70-80ns parity simm modules
You may be able to make it work with larger simms, though no guarantees.

Digi-Key part list - Copy the below to a CSV and import:
Index,Manufacturer Part Number,Manufacturer Name,Description,Attrition %,Requested Quantity 1,Pack Quantity 1,Pack Type 1,Digi-Key Part Number 1,Unit Price 1,Extended Price 1,Minimum Order Quantity 1,Customer Reference
1,BDL-110-G-F,Samtec Inc.,CONN HEADER VERT 20POS 2.54MM,,4,4,Tube,SAM10910-ND,11.59000,$46.36,1,"PL1, PL2"
2,110-44-314-41-001000,Mill-Max Manufacturing Corp.,CONN IC DIP SOCKET 14POS TIN,,4,4,Tube,ED90049-ND,0.75000,$3.00,1,V1-V4
3,C315C104M5U5TA7303,KEMET,CAP CER 0.1UF 50V Z5U RADIAL,,4,4,Cut Tape (CT),399-9859-1-ND,0.23000,$0.92,1,C1-C4
4,UMP1A100MDD,Nichicon,CAP ALUM 10UF 20% 10V RADIAL,,2,2,Bulk,493-15546-ND,0.47000,$0.94,1,"C5, C6"
5,CFR-25JB-52-2R,YAGEO,RES 2 OHM 5% 1/4W AXIAL,,18,18,Bulk,2.0QBK-ND,0.06700,$1.21,1,R1-R18
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Thank you Harrison for all this great work. I would like to build and test one do you have a pcb I could use or a way for me to print one myself thanks in advance. I'm familiar with pcbs and soldering.
 
harrison.frazier said:
I've been working on a RevC and a set of instructions for assembly, though life got in the way and had to put the project aside. I need to finish the design and order a test board!

I have the parts to do a 40mhz mod but I'm afraid that it may push the chips of the inboard too hard as they already get hot.. Someone else's stopped working after the overclock so I'm weary to do mine. The Cyrix 486 upgrade chip does make a big difference and WFW 3.11 seems to fly compared to 3.1.. Maybe because it's got more of it written/compiled for 32-bit CPUs..


View attachment 1260674
Click to expand...
Would proceed with caution I still mourn the death of my inboard… nudge nudge anyone with the prowess to repair a board then do let me know..

The new board design looks great having the jumper to change to a 4mb is a good improvement.
 
Mike1978 said:
Would proceed with caution I still mourn the death of my inboard… nudge nudge anyone with the prowess to repair a board then do let me know..

The new board design looks great having the jumper to change to a 4mb is a good improvement.
Click to expand...
Mike was it the ram expansion you think caused the issue on your inboard. I'm hesitant now to try it.
 
Mike1978 said:
Would proceed with caution I still mourn the death of my inboard… nudge nudge anyone with the prowess to repair a board then do let me know..

The new board design looks great having the jumper to change to a 4mb is a good improvement.
Click to expand...
I would reach out to Adrian his youtube channel is here. I bet he could fix your board he is awesome!
Good luck!Screenshot_20230904-084123_YouTube.jpg
 
There is nothing particularly crazy about fixing an inboard (correct me if I am wrong here but thats to the best of my knowledge) ... you just need to start replacing logic and reprogramming PAL/GAL chips with a known good CPU until it starts working again... or pull the chips and test etc... might be a bit safer.
 
cb88 said:
There is nothing particularly crazy about fixing an inboard (correct me if I am wrong here but thats to the best of my knowledge) ... you just need to start replacing logic and reprogramming PAL/GAL chips with a known good CPU until it starts working again... or pull the chips and test etc... might be a bit safer.
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There’s a fair amount of chips on the board. If the chips in situ could be tested in some way I think that would be much more progressive than removing them all. However I’m certainly not the expert..

Sadly I don’t have the skills or equipment to do this or the know how.. but I’m hopeful someone out there can
 
saifbadri said:
Mike was it the ram expansion you think caused the issue on your inboard. I'm hesitant now to try it.
Click to expand...
No certainly not the ram, I changed the clock crystal but also I potentially had a short across two pins with the ram board but the ram daughterboard was in no way responsible for the death of my board so far as I know.
 
Mike1978 said:
There’s a fair amount of chips on the board. If the chips in situ could be tested in some way I think that would be much more progressive than removing them all. However I’m certainly not the expert..

Sadly I don’t have the skills or equipment to do this or the know how.. but I’m hopeful someone out there can
Click to expand...
That would be an effort of futility... you pretty much have to remove them to test them. Especially since the inboard uses these chips at the upper limit of their performance in many cases.
 
Ok, revision C is tested and working, with assembly instructions! (Note the jumpered resistor spots.. I think they may not be necessary because it works just fine...)

I have 3 blue boards on hand and can order more if there is more interest. I will provide the simm sockets as well. The rest can be found on digi-key.
PM me if you're interested!

IMG_8855.JPG


Mike1978 said:
No certainly not the ram, I changed the clock crystal but also I potentially had a short across two pins with the ram board but the ram daughterboard was in no way responsible for the death of my board so far as I know.
Click to expand...
Yeah I wouldn't suspect anything that the ram, I've put 30+ hours on my XT with the latest rev and It's solid. I think one of the chips was overdriven by the higher clock signal?

One thing I did was add a fan that blows over the board because these chips get quite warm even when left in the stock configuration! 🔥
 
Thank you Harrison, this is awesome!
I can't wait to get mine and build it. I ordered all the parts already.
Would the little jumper and it's pin header for selecting 4/2MB be included? I hope you can send me one if you have extras. since this was not in the BOM you shared. thanks
 
saifbadri said:
Thank you Harrison, this is awesome!
I can't wait to get mine and build it. I ordered all the parts already.
Would the little jumper and it's pin header for selecting 4/2MB be included? I hope you can send me one if you have extras. since this was not in the BOM you shared. thanks
Click to expand...
A piece of wire works to jumper since you're planning to use it as a 4MB module :)
The 2MB is just an option as the original piggybacks had these hardwired based on their capacity, and I left it open for testing and maybe if someone only had 256K sticks.
 
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