That's an interesting board. Congratulations for your patience, it's always nice to see such an extensive (and succesful) repair!

Incredibly good work you made there....! And the board is also very nice. How many hours did you spend on this..?

Well done. You can't have enough ram.

Dusting off this topic 😀

That's a very nice rebuild indeed, McBierle! A friend of mine gave me an old big tower with a similar but slightly older C386 mainboard. This one is the 25Mhz flavour 😉
Mine is also completely destroyed by the evil Varta and there are a few parts missing like the CPU, the cache controller and the 32-bit external memorycard.
This memorycard seems to be unobtainium so I was wondering what type/brand this unit is... Looks to be an "ISA130" card but I have no idea what search term to put in the old googly box to find even a single picture of one.. The only picture I found was your giant card with 16 SIMM sockets but I have no idea what brand/model number/FCC ID this thing has. Could you help me with that? Very much appreciated! 😀

My 386 board has a similar bonkers '32 bit RAM slot':

https://stason.org/TULARC/pc/motherboards/D/D … BACK-CACHE.html

I also have no idea what's meant to go in there, or why it would be useful when the board has SIMM space for the full compliment of RAM possible? Maybe to allow you to upgrade without spending on new RAM?

McBierle wrote on 2019-06-01, 21:05:

Hi, i wanted to share this little story of a 386 motherboard (and me).

Hi McBierle,

Could you please post some pictures of the 32-bit memory expansion card that came with your C386 mainboard? I would appreciate this very much as I got one of these mainboard from a friend.. Mine is a C386-25 and it does POST but it lacks the memory board which seems unobtainium rendering this thing of beauty entirely useless as far as I know.. I've been searching for weeks for boards like these but the only info I could find is your post.. I wonder if that memory card is somehow standardized or has a type / brand badge on it.. It's also unclear who manufactured these mainboards. Mine only has a label "Celem" on it which appears to be a reseller from Belgium (I'm in the Netherlands). It also has no FCC id so it's next to impossible to determine what this alien board even is 😉 The only thing printed on the board itself is "C386-25" and "Made in Taiwan R.O.C." which is about as generic and useful as "This is a thing" 😉
Thanks in advance for any extra pictures of this memory board you may want to share if you're still active here on Vogons!

Cheers!

+1 please post pictures of the memory card back and front.

Its interesting to see its not just SIMM slots but has logic chips onboard, thankfully they all look standard 74 series and not custom programmed PAL/GAL so reproduction is entirely doable.

pipmastah wrote on 2023-09-27, 22:25:

Hi McBierle, […]
Show full quote

McBierle wrote on 2019-06-01, 21:05:

Hi, i wanted to share this little story of a 386 motherboard (and me).

Hi McBierle,

Could you please post some pictures of the 32-bit memory expansion card that came with your C386 mainboard? I would appreciate this very much as I got one of these mainboard from a friend.. Mine is a C386-25 and it does POST but it lacks the memory board which seems unobtainium rendering this thing of beauty entirely useless as far as I know.. I've been searching for weeks for boards like these but the only info I could find is your post.. I wonder if that memory card is somehow standardized or has a type / brand badge on it.. It's also unclear who manufactured these mainboards. Mine only has a label "Celem" on it which appears to be a reseller from Belgium (I'm in the Netherlands). It also has no FCC id so it's next to impossible to determine what this alien board even is 😉 The only thing printed on the board itself is "C386-25" and "Made in Taiwan R.O.C." which is about as generic and useful as "This is a thing" 😉
Thanks in advance for any extra pictures of this memory board you may want to share if you're still active here on Vogons!

Cheers!

Sorry was a long time not here. Somehow i forgot to set email notofications. Some Pics...

Thank you!
So the memory board is called "386RC-16". Indeed only 244, 240 (why inverters?), and bunch of 32 OR gates. Easy to replicate.
Your motherboard looks related to MODULAR CIRCUIT TECHNOLOGY MCT-C386-33/40
https://stason.org/TULARC/pc/motherboards/M/M … C386-33-40.html https://arvutimuuseum.ee/th99/m/M-O/32479.htm

ChrisXF wrote on 2023-07-30, 11:51:

My 386 board has a similar bonkers '32 bit RAM slot':
https://stason.org/TULARC/pc/motherboards/D/D … BACK-CACHE.html

different slot, another MODULAR CIRCUIT TECHNOLOGY mobo uses same slot https://theretroweb.com/motherboards/s/modula … -mct-m386-20-25

McBierle wrote on 2024-10-23, 17:45:

If that machine still exists:
Can you run ctcm from heise?
I'd like to see whether you have a problem with cacheable area 😀

Disruptor wrote on 2024-10-24, 08:24:

I'd like to see whether you have a problem with cacheable area 😀

cachechk shows whole 16MB cached?

pipmastah wrote on 2023-09-27, 22:25:

Could you please post some pictures of the 32-bit memory expansion card that came with your C386 mainboard? I would appreciate this very much as I got one of these mainboard from a friend.. Mine is a C386-25 and it does POST but it lacks the memory board which seems unobtainium rendering this thing of beauty entirely useless as far as I know.. I've been searching for weeks for boards like these

pipmastah how motivated are you about that ram board?
I was bored and checked if it would be possible

only routed few lines, but it all makes sense. Still might only be possible with some more extensive McBierle help (more pictures with no simms, at better angle/lighting, and crucially some continuity measurements on the finish line) + you tracking slot pins to nearby chips.

Disruptor wrote on 2024-10-24, 08:24:

If that machine still exists:
Can you run ctcm from heise?
I'd like to see whether you have a problem with cacheable area 😀

Bad news. I took the board from "cold Storage" and tried to do as you requested but there seems to be a short somewhere with the 12v lane. I'll try to find the cause, but as always problem with to few time.

rasz_pl wrote on 2024-10-30, 11:58:

pipmastah how motivated are you about that ram board? I was bored and checked if it would be possible […]
Show full quote

pipmastah how motivated are you about that ram board?
I was bored and checked if it would be possible

The attachment 386RC-16.jpg is no longer available

only routed few lines, but it all makes sense. Still might only be possible with some more extensive McBierle help (more pictures with no simms, at better angle/lighting, and crucially some continuity measurements on the finish line) + you tracking slot pins to nearby chips.

I would certainly help where and if i can. I would even send the board per mail.

McBierle wrote on 2024-10-30, 20:11:

Bad news. I took the board from "cold Storage" and tried to do as you requested but there seems to be a short somewhere with the 12v lane. I'll try to find the cause, but as always problem with to few time.

Surprising considering you replaced tantalums sitting near the AT power connecter. I hope its nothing major.

McBierle wrote on 2024-10-30, 20:11:

I would certainly help where and if i can. I would even send the board per mail.

That would be fantastic. Im still in the very early stages of assessing feasibility of this endeavor. PCB this size + parts + shipping is going to end up around $100, and so far You and pipmastah are the only people to ever have one.
I hope to b able to get it up to ~70-80% completion before needing more help by logic deduction alone. Im interested if I can guess what the chips are doing by just solving it like a puzzle 😀

Hello Police? I would like to report a crime. An Asian gentleman murdered signal integrity on several tracks 35 years ago!
Yes, I have witnessed the whole thing. Data bus on the power layer with address bus right above it. Address bits 0 and 1 right over data bits 6 and 7.
Yes, exactly, no ground whatsoever at ~30MHz.
I agree, manslaughter charges would be appropriate.

In other news its done 😁 and boy was it fun!

90% done to be precise 😜
- slot placement is hard from picture alone
- dimensions are slightly off and needs measuring clearances
- hard to guess which pins are 5V or ground on the connector. Half of them has tantalums with painted ground pin, but the other half doesn. Better to verify.
- I didnt bother with capacitors before confirming dimensions
- most importantly whole CAS situation needs few more pictures or measurements because previous pictures had dust bunnies 😁 Too many tracks run under 74F32 chips to attempt an educated guess 🙁 82C302 generates 4 CAS signals but this board takes 8, very possibly pairs of pins are joined on the motherboard. solved, would only need sanity check in continuity mode.

McBierle could I bother you for a few more pictures? It doesnt look like pipmastah will be back so that would be strictly to satisfy my curiosity. Front of the board with simms removed concentrating on
- gaps between simms so I can confirm/compare against my work. That was a fun and challenging part to route.
- center of the board on U7 U7 U8 U9, Im interested in pictures at an angle with good lighting/flash. Maybe with any luck I could peek under the chips a little 😀
- picture of motherboard lower right corner, slot and three C%T chips
- picture of the motherboard memory slot from the back

Messy diagram, too big to upload as png

I think I found another motherboard sharing same Chips & Technologies CS8230 chipset, bios (EC&T-1331-040990-K8 while OP one is EC&T-1190-040990-K8) and maybe ram board pinout https://theretroweb.com/motherboards/s/ecs-386a, minus the cache.

Good sleep and 17 hours later I understood the CAS driving mechanism in just few minutes of staring at it 😁
Whoever designed this memory card made sure its flexible enough to be able to work with different memory controllers (or interleaving configurations). One set of 4 CAS pins drive consecutive SIMM sockets in a Bank, the other set drives whole banks per CAS line. Brilliant. Tracks under chips line up perfectly.

EDIT: uploaded whole RE job to github https://github.com/raszpl/386RC-16
I also found predecessor to McBierle C386-33, Modular Circuit Technology MCT-386-M. Date on a sticker 1.9.87. 386DX 20 and IIT FPU 387 20Mhz.

and earlier version of proprietary memory card, pre SIMM!

matze79 uploaded those pictures to https://dosreloaded.de/forum/thread/330-modul … ze-at-mainboard in 2017