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Considering an S-100 "replica" of sorts

Grindar said:
pretty similar ideas, and not bad. They sound intriguing, and alleys to be explored if what I want to do doesn't pan out. I'm going to end up with something like an SBC, anyway, with a display and expansion slots. It'll be a large, expensive board, but really, isn't it just as expensive to get 2 or 3 different boards for the same circuits?
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Hi!

Well with either approach you can build something and get it working (N8VEM or P112) which is worthwhile. I recommend an incremental build rather than doing everything all at once. I think building on an existing platform and leveraging it may be a lower risk, lower cost method than a pure "from scratch" ground up approach.

Making a large PCB is expensive and risky. Making several smaller ones is also expensive but in a different way. The difference is by using several smaller boards you can better customize and isolate problems easier. With a single large PCB, you have to design everything all at once *and* get it right the first time since there is no going back. Changing the circuit in a PCB after it is manufactured is difficult and messy. It can be done with "cuts and jumpers" but I try to keep those to a minimum.

The WaveMate Bullet and Ferguson Big Board are "all in one" SBCs and they are fine but represent some high end expertise to create such a complex devices.

Now that EBC to S100 circuit, how easily could it work the other way? Adding EBC slots to an s100 computer? I would think it's mostly just matching up i/o lines, right? I'm not familiar at all with the EBC, and my Google Fu is weak tonight, apparently.
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Yes. S-100 to ECB would be similar but I don't have a circuit schematic. Since ECB is basically just the Z80 bus fully buffered it would be easy to just export the Z80 pins to an ECB connector. Due to the timing issues, it would probably be more difficult to go straight from S-100 to the ECB but I am sure it is possible. I don't have a design to do that though and have never heard of or seen one either.

Well, the nice thing about "re-inventing" it is that I understand every bit of it from the ground up. The only reason I choose to use someone else's schematics at all is because I don't think I've had enough classes in electronics to design it completely from scratch, though I've had enough to know what the components are doi8ng where they're placed, to an extent. I'm using this as a way to teach myself. I want to understand what every "wire" is there for...even if I never physically build it, I learn. That's why I'm getting ready to print out these ZPU schematics on 11 x 18 and hunt down a seemingly reliable version of the s100 bus and spend probably an hour or two just making notes on which lines on the schematic do what...though this'll probably wait until I finish downloading all the datasheets for the components. Darn this dialup! I live like 3 miles away from where I'd be able to get DSL...and no cable, either.
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Yes, few things will teach like building your own home brew computer. I have learned much with TestPrototype and now the N8VEM project.

Good luck with your project and let me know if I can help out.

Thanks!

Andrew Lynch

PS, the P112 (as is the SB-180) is a fine SBC and they are very nice, however, it is my understanding they are not available. Possibly you could find a used one for sale or incomplete kit or broken unit? If so, please let me know as I would like to get one myself. However, I do not think they are available and have not ever seen one for sale in any form. Please let me know if this is incorrect. Thanks!
 
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Well, small update, I do believe I've found how I'm going to make my enclosure:

http://www.geocities.com/homemadecpu/aidil/index3.htm

It's just so...beautiful...And by the looks of it, fairly cost-effective.

Of course, I probably won't have as many output LEDs as the Magic-1...

This weekend should work out well for research, I have nothing that I know of planned.
 
Hi!

The home brew CPU case is definitely nice but personally, I would concentrate on making the electronics work first. I do all my stuff with bare boards. Once the system is more fully functional I'll start doing something about case.

My current thinking for cases is to re-use an old mini tower case and drill some holes in the bottom for nylon stand-offs. Then mount the ECB backplane to the stand-offs. By using DIN 41612 and ECB format boards they are strong enough to stand freely without extra mounting. That should be a good temporary solution.

At some point in the future, I may start looking at a card cage design but that is so far off as to be not on my list yet. Then we'll need a metal bender or plastic forming to make the guides. Cases are nice but only if they contain working computers IMO.

Thanks and have a nice day!

Andrew Lynch
 
Hi Terry!

There is a computer case history museum? ;-)

I suppose there are a few exceptions... The original wooden NorthStar Horizon is a nice case and the original IBM PC/XT/AT. Maybe some of the S-100 crates like the VG, CompuPro, or Cromemco.

However, most cases are of the XT/AT clone variety and are barely worth anything except maybe as scrap metal. They take up a lot of space and are just in the way during repairs. In recent years, the quality of the cases has deteriorated and are now very thin metal and weak. I have sent more than a few to recycling after stripping out anything of value.

Thanks and have a nice day!

Andrew Lynch
 
Well, of course :cool: I mostly just posted that link here so I can refer back to it later in case of hard drive failure in the lappy.

Now an idea occurred to me yesterday. Those DIN 41612s, what if I were to use two of them per card, and do the multiple cards? I didn't see it, but I guess they're about 4" wide, assuming the pins are .1" apart, right? Anyway, the thought is, 2 of them side by side, and for running bus lines, just ignore the middle row. Eliminates a lot of work routing lines to them, simpler to solder, reducing my chance of screwing up, retains the mechanical strength of the wider connector. Would force my card to be at least 8 or so inches wide at the minimum, but maybe it'll be made up for by a lower profile.

Your thoughts on this, before I start playing around in eagle?
Also, anyone got a source on s100 slots for integrating onto the m/b? OR I could possibly rig up some kind of adapter that would run from the 41612s presumably maybe a couple couple inch long ribbons, which are on a pcb that is basically just an s100 stab, to be placed into a real s100 motherboard. Maybe a real s100 extender could be modified. Any input on this is welcome too!
 
Grindar said:
Well, of course :cool: I mostly just posted that link here so I can refer back to it later in case of hard drive failure in the lappy.

Now an idea occurred to me yesterday. Those DIN 41612s, what if I were to use two of them per card, and do the multiple cards? I didn't see it, but I guess they're about 4" wide, assuming the pins are .1" apart, right? Anyway, the thought is, 2 of them side by side, and for running bus lines, just ignore the middle row. Eliminates a lot of work routing lines to them, simpler to solder, reducing my chance of screwing up, retains the mechanical strength of the wider connector. Would force my card to be at least 8 or so inches wide at the minimum, but maybe it'll be made up for by a lower profile.
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Hi,

DIN 41612 connectors come in a variety of pin counts. Some ECB configuration use the 96 pin type and just use the outer rows. That gives 64 pins which is quite enough for a Z80 style bus.

You could use an entire 96 pin to route all S-100 pins (several pins are unassigned or duplicates). I have had no problems routing all 96 pins with KiCAD using a 2 layer board.

When I did the ECB backplane, I needed to manually route the traces due to complexity but still it was no problem with a two layer PCB.

I think VME is similar to what you describe as it uses two Eurocards side by side. There are extensions which use dual DIN 41612 connectors.

If you want to preserve the routing of the S-100 card maybe the dual 50 pin header approach may work better. I think the Heathkit "Benton Harbor" bus does something similar as it is a single row of pins the card connects to.

Your thoughts on this, before I start playing around in eagle?
Also, anyone got a source on s100 slots for integrating onto the m/b? OR I could possibly rig up some kind of adapter that would run from the 41612s presumably maybe a couple couple inch long ribbons, which are on a pcb that is basically just an s100 stab, to be placed into a real s100 motherboard. Maybe a real s100 extender could be modified. Any input on this is welcome too!
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Well, try lots of configurations until you find one that suits your preferences.

There are S-100 compatible edge connectors available but you'll find they are not easy to find. Try Unicorn Electronics as I think I bought some replacements from them a while back.

Thanks!

Andrew Lynch

PS http://catalog.tycoelectronics.com/...54/290?RQS=C~1^M~BYPN^PID~213499^PN~1612163-4

if you do find a supplier, please post the URL here as I am sure there will be lots of interested hobbyists.
 
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There was a possible match at unicorn for a wire-wrap connector, wasn't much about it.

If anyone knows how to enhance the image enough to make it legible, the brand name on the side of the connector on the altairkit motherboard is just too blurry to be read...I can make out either electronics or electronica as the last word, and highly doubt that it's electronica. Maybe one of you can guess the manufacturer from what's visible? I'll email Mr. Stockly tonight, if I remember, and see if he'll share his source with us.

UPDATE: Found it in another picture. It's from www.sullinselectronics.com, part number EBA50DRTH. Digikey sells them, at 16 or so bucks a pop, in 10 packs. A bit more than I want to spend on connectors, but if I can split an order with somebody later on, that won't be bad. I just can't justify 160 dollars on connectors when I only need 2 or 3 tops.

I've spent the last couple days flipping through catalogs, looking at connectors. I think I'm gonna go with my double-wide 41612 idea. Lets me pretty easily preserve the bus, while not forcing me to solder that middle row, which is what really terrifies me, my hands tend to shake when doing that precise of work.

The backplane is a secondary concern for right now, so I have time to find the s-100 connectors, and if I don't, I can always leave them off, for a future rendition of the backplane.

So I can make sure I don't forget anything, what do you guys like to have on the front panel. Address and data value switches are obvious. LEDs for address and examine would be standard too, I suppose. Another row of LEDs to indicate value of switches? LEDs are a lot cheaper now, better to have a couple too many than kick myself later.

Tonight's a coin-toss, start digging through memory schematics til I find something I like or can modify pretty easily, or start dropping stuff into a schematic in eagle. Really, it's gonna hinge on how much longer I can look at a computer screen today. Been working with group policy all day.
 
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I was thinking that you could put the connectors on the top of the boards and use old 50-pin SCSI cables (which must abound) to distribute the signals and a strip PCB running perpendicular to the channels holding the cards to distribute the power. The strip would also allow you to use smoothing caps.
 
I'm designing the m/b anyway, smoothing caps are an option...

I elected not to do it the original way I was thinking with the ribbon cable bus because I had forgotten to consider the distance the clock would have to travel. It could be minimized, but there were better alternatives.

With your idea, I'd have to still have a mechanical mount on the "bottom", which means I'd still have to set up a similar connector or at least a bracket on the bottom. Not to mention I'd still have to dream up an s-100 adapter...which I insist on doing, so I can pick up parts like a floppy drive/controller later and essentially plug it right in.

Just curious, anyone know where to find documentation of the Extensis ex3000? Google didn't turn up anything, and though I wouldn't want to implement it, I'm curious to see how they rigged the multiple processors on the bus "in action"

Another thought for displaying status of switches: lighted toggle switches. I know I saw some somewhere...
 
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If I was after recreating something with a standardized bus, I'd probably look at Multibus I before S-100, unless I had a lot of S-100 cards already available.

Multibus is older than S-100 and better designed. Instead of the 100 pin edge connector it uses an 86 pin connector with wider "fingers".

If I wanted a smaller profile, I'd probably pick STD Bus.
 
If I was after recreating something with a standardized bus, I'd probably look at Multibus I before S-100, unless I had a lot of S-100 cards already available.

Multibus is older than S-100 and better designed. Instead of the 100 pin edge connector it uses an 86 pin connector with wider "fingers".

If I wanted a smaller profile, I'd probably pick STD Bus.
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Profile's not really an issue, for except considering the cost of the pcb in square inches :mrgreen:.
I'm fabricating my own enclosure, and most of my own cards. I'm sticking with the s100 because I fell in love with the altair, and when I finally get enough $$ I either want an original or a replica kit.

I'm not bothering with card edge connectors for anything I'm designing, going with the connectors that we talked about for like an entire page, so finger width isn't a concern. I'm only attaching a few s-100 slots for when I can scrounge up some vintage equipment (gotta be lurking in a closet at work somewhere).
 
Hi!

MultiBus I *is* a much better designed bus than S-100. It is well thought out, extremely reliable, and generally very tough. On my previous job they had original MultiBus I machines running in the labs under very heavy duty cycles and in a rough environment for many years. We bought spares but the cards almost never broke. They were/are awesome machines and are no doubt still chugging away today. I'll bet those machines are at least 20 years old and maybe older than 25. Nice!

MultiBus, S-100, and STD all use edge connectors so making prototypes is expensive. Also getting the connectors themselves is no easy task either. As a result, I recommend either ECB bus which I already mentioned or the STE bus since both use DIN 41612 connectors. As a result making your own prototype boards will be much less expensive.

http://en.wikipedia.org/wiki/STEbus

Grindar, have you considered just building an N8VEM SBC and ECB backplane system and then building some peripherals? I sure could use some help on the project and if you are interested in home brew computing, that would give you a big head start for low cost. It is also something you can do now rather than in months.

Your ideas for a display and input terminal are good. Please consider and you are welcome to join up on N8VEM regardless.

Thanks!

Andrew Lynch

http://groups.google.com/group/n8vem
 
There was a low-cost hobbyist system in the 70's that I recall. I believe it was called "Jolt" made by a couple of guys in Los Altos. It used ribbon cable as a bus to hook together various boards that were simply stacked with threaded through-rods and spacers.

I would have gladly traded my MITS 8800 and my Integrand S100 box for a Multibus MDS-80 any day of the week in a flash. Andrew's right that those things were industrial-strength. I recall that a few friends and I had a discussion as to whether there were more S-100 or Multibus boxes made. After I pointed out that Sun, SGI and HP/Apollo used Multibus in addition to Intel, it was no contest. I think one can still buy Multibus boards.

A previous poster remarked that DRAM is not to be toyed with lightly. My Altair had 2 4K DRAM boards in it; used the TI 4Kx1 DRAM chips. It was miserable--dropped bits every time you hit the reset switch.

You know, designing the whole affair using SMT is a very viable option--why not build a replica half- or quarter-size?
 
Sorry guys, work's been keeping me busy. Darn these kids and their desire to wreck everything the District owns! OK, enough griping, on to computers!
You know, designing the whole affair using SMT is a very viable option--why not build a replica half- or quarter-size?
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Because SMT is terrifying to me. My hands get jittery, ironically enough, the more control I need. I can handle DIPs fine in short bursts, but it gets bad after a little while. I am planning on picking up one of those SMT practice kits I've seen around, but I'd not like to build a project this complicated as my first real experience with it.

I got in a couple s100 edge connectors saturday in the mail, so that more or less finalizes it. A colleague had some stored with his electrical gear at home (across the state) so he had his parents mail 'em on over. I have 2, if I need more I'll have to buy them or scrounge them.

I'm actually satisfied with the bus I selected, even if isn't industrial-strength, and it's rather picky to build it for...all the more endearing to me.

When you first mentioned it, I checked out the N8VEM, something just didn't click with me, unlike this ZPU...I can't put my finger on it. I am considering a move to KiCad before I get started with any serious circuit drawing...how is it compared to Eagle? I rather like how eagle works, but I can put KiCad on my ubuntu box at work for those odd afternoons the kids don't destroy something, and we don't have a single bad port take a campus offline(seriously, 3 bad superstack ports in one week, on 3 different campuses?)

Backplane, given my current supply of of s-100 connectors, I'm thinking those 2, and 6 of the double-Din-41612s I've been planning on, 3 for currently planned cards, the other 3 for later expansion with custom-made cards. I shouldn't need more than that, right? Or would you recommend kicking it up to 12 total slots, being 10+2.
 
Hi! Long time, no hear! What's the latest on this project?

Thanks and have a nice day!

Andrew Lynch
 
Poorly, though not due to any element of the design. Just haven't had much time between work, class, and homework. This weekend's looking good and open though.

As of right now, have the z80 and some of the addressing logic done (really, really haven't had much time for anything...got a pile of pre-ordered video games waiting for their turn too). Really not too shabby given the amount of free time I've actually had and the fact that I'm learning how to use Eagle at the same time.
 
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