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MBC-XT clone mainboard circuit board

tipc

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I got this thing on eBay a few years ago. That's all it is, a bare mainboard, etched, drilled, wave soldered presumably.

Anyone have any info? Besides a Compaq Plus portable and the Leading Edge Model M ... oh and the AMT ATjr ... and the Victor VPCII, I don't own any actual compatibles. Yeah then there's the Ampro LittleBoard/PC. And my Zenith Minisports. I think that's all. Could use an actual clone. Is it worth my time? Just wondering if anyone out there has undertaken it's construction. Looks well made enough.
 
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Hi, That board sounds really interesting! Could you please post a few photos... possibly a scan of the front and back? Also, I have a scan of the Big Blue Book somewhere, but the quality is not very good. (Looks like it was a scan of a bad photocopy.) I'll see if it can find it if nothing better turns up....

Edit: Turns out I actually have a pretty good copy of the Big Blue Seed: Here is a temporary link. Somebody should grab this for archiving...

http://www.mtmscientific.com/Big Blue Seed.pdf Michael
 
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Ok, first off be advised you're not dealing w/someone who deals a full deck. I really don't want to further guess what THE ACTUAL NAME IS, but I think it's in reality MBE.

Forging ahead, I may be able to photograph it in the next few days (very glad to see there's interest). There was also maybe 2 sheets of instructions, scanned and discarded, like so much other ephemera I've accumulated over the years. Finding it will be a Herculean task. But the main board is accessible. I had it out a week ago.

I also had my crusty AMT ATjr/AMTjr out briefly today (raining, during a brief let up). Turns out the motherboard RATHER SNEAKILY AND MYSTERIOUSLY RESEMBLES AN ACTUAL 5150 MAINBOARD'S LAYOUT. Huh. How did that happen? If you don't know the back story of the AMTjr A.K.A. ATjr, I suggest you take a look at this:

https://books.google.com/books?id=V...&ved=0CCoQ6AEwAg#v=onepage&q=ATjr ibm&f=false

then this:

https://books.google.com/books?id=s...ved=0CCAQ6AEwAQ#v=onepage&q=AMTjr ibm&f=false

My unit says 'AMTjr' on the outside, but the BIOS screen at boot still says 'ATjr'. Must be a late model. I'll take photos of that when it stops raining.

It and a mangled IBM PC/XT box (w/a 5150 mobo, yes they cut the hole for the keyboard jack) I bought out of some guy's store front a number of years ago. I gave him 25$. I could hear him bragging to his buddy how he took me to the cleaners for old junk. But he who laughs last laughs the loudest. I proudly am 1 of the few people alive on planet earth (the other guy is in Senegal I think) who can brag they have an actual ATjr. Muahahahahaha
 
Boy, I'd love to get my hands on some of the boards they describe the assembly of, in the "Big Blue Seed" book. Too bad they don't include schematics, or I might attempt to re-create them.

It's too bad that we almost never see those build-your-own PC motherboard kits on eBay. I've been looking for years, without success.

Thanks!
- Alex
 
When I first glanced at that board, I would have swore it was identical to mine (that is another instance of the MBE-XT).

I can scan the board, as long as it isn't multi layer, they *can* be reliably etched at home (I'm made to believe, haven't attempted the specific procedure yet). Then all you need is a lot of patience, or a cnc mill/drill. If someone didn't want to go the whole 9 yards, you could build a manual screw driven drilling fixture and do it that way.
 
I have a CnC, so drilling a board really isn't a problem.

tipc, have you considered making an AT-clone board? I'd enjoy building one of those, as well. I'd think anything up to a 386 should be doable, as boards without custom logic did exist. I really enjoyed building your PC-clone kit.

Thanks!
- Alex
 
I'm not CEO of that company. Never even been to Michigan.

And frankly, even though I myself find the original IBM mobo interesting, I have no intention of recreating IBM's offerings all the way up to the present.

That is if I were to produce and offer for sale a retro project, it would be something else. Something more obscure. IBM IBM IBM BLAH! So boring. Y'all need to branch out and get interested in all the other stuff weirdo offshoots.

ajacocks, if I ever decide to produce a retro P4 (genuine IBM!) mobo w/SpeedStep Technology (TM), I'll PM you.
 
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Whoops, wrong person. I confused you with mmruzek.

Why would you guess that anyone here only likes PCs? Seems like a silly assumption. Personally, I just enjoy building my computers, and will work on almost anything that requires soldering.

- Alex
 
It's similar to a lot of things, including a 5150 mainboard. Now if I can just find some cheap sockets . . .

I already have an AMT ATjr/AMTjr, which also resembles this board. Stopped working a while back, but I'm guessing it was just corrosion.

Anyone want to venture a guess of how many 5150 main boards and copies were produced?
 
Thank you for posting a photo. If you have access to a scanner it would be useful to do a high resolution scan of the front and back. Especially with the board only being double sided, it would be possible to use the scanned artwork to create a PCB layout. Even a free PCB layout program like ExpressPCB should be able to handle this.
 
I'd think anything up to a 386 should be doable, as boards without custom logic did exist.
I've personally never seen one, but that doesn't mean they don't exist. What's the lowest speed 386 board you've seen (10MHz or so, probably? The slower, the better for the 74xx glue logic).

In any case, this is certainly interesting. I wasn't under the impression that companies actually made their own clone kits for PCs back in the day. Though since IBM didn't technically patent the design, just the BIOS, I guess I shouldn't be too surprised.

Re: the similarity between all clones that tipc and others mention... I guess that's solely because there are only so many ways to do address decoding, keyboard (3 TTL chips), and parity circuits, etc while meeting propagation delay requirements. Although I find the PAL in alecv's picture of an ERSO board a curious addition.
 
The slowest 386 board that I have seen was a 386DX-16, which was pretty darned early.

There is higher-speed 74-series logic available, that should be able to function up to the speed of any reasonable 386 (33 MHz, at least), since I have used similar logic to build high-speed Z80 systems, that are up to 33 MHz.

Anyway, if a 386 is a bit ambitious, a nice 286/AT clone might be a fun build, too.

- Alex
 
The slowest 386 board that I have seen was a 386DX-16, which was pretty darned early.

There is higher-speed 74-series logic available, that should be able to function up to the speed of any reasonable 386 (33 MHz, at least), since I have used similar logic to build high-speed Z80 systems, that are up to 33 MHz.

Anyway, if a 386 is a bit ambitious, a nice 286/AT clone might be a fun build, too.

- Alex

74AB(T), 74AC(T), or 74F, right? I'm actually using that to build a 10-14MHz design (not PC-related) right now. Just something to think about (386 custom kit) in the future...
 
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