The SBC6120 is a replica of a 1960s/70s vintage DEC PDP-8 computer. It uses the Harris HD6120 "PDP-8 on a chip" CPU and started off as a single board computer the size of a 5-1/4" hard disk (and hence the name, "SBC6120"). Everybody wanted a lights and switches front panel, and a couple of years later I designed the FP6120 ("Front Panel 6120") that you see in the photos. The SBC6120 is fully operational and functional without the front panel - this is handy when assembling the kit, because it's possible to assemble and test the SBC6120 before the front panel is finished. The reality is that no one ever wants one without the other, and so the SBC6120 and FP6120 are always sold together as a set.
The HD6120 CPU used in the SBC6120 is the same one used in Digital's DECmate "personal" computers and is fully software compatible with a PDP-8/E. The front panel is fully functional and has the same complement of lights and switches as a real PDP-8/E. It measures 15" by 8-1/2" and is about 3/4ths scale when compared to a real PDP-8. The SBC6120 will run most software written for a PDP-8, including DEC's OS/8 disk operating system. The SBC6120 has an IDE disk interface that can be used with a real drive or (more commonly these days) a CompactFlash card or SSD.
To Learn More
- Steve Gibson of Gibson Research Corporation, has produced a wonderful video that introduces the SBC6120/PDP8 and describes its operation at http://www.grc.com/pdp-8/showandtell-sbc.htm
- I have a web page about the project with lots more details at http://www.sparetimegizmos.com/Hardware/SBC6120-2.htm
- There are complete manuals for the project, including assembly instructions and parts lists, at http://www.sparetimegizmos.com/Downloads/SBC6120.pdf and http://www.sparetimegizmos.com/Downloads/FP6120.pdf
Remember - the goal of this project is simply to purchase the custom parts needed to build an SBC6120. You'll still need to supply some parts (resistors, diodes, standard 74HC ICs, etc) and you'll need to be able to put everything together. The manuals referenced above contain detailed instructions and parts lists, and you should review them and consider whether you'll be able to do this. If you're unsure, you might want to buy an assembled and tested unit.
Note - the photos show white switch paddles, however depending on the supplier's stock we may end up with black paddles. The switches are the same either way; it's only the color that differs.
If you're not sure you have the skills to build yours, or you simply don't have the time, then for a pledge of $999 or more I'll assemble your unit for you. Assembled units include all PCB mounted parts and a USA standard power supply. You'll be able to plug it in and use the front panel as soon as you receive it. Assembled units do not include any frame or enclosure, a disk drive, nor a terminal.
I have enough CPU chips to build 30 units. That's it, and there is no ready source for more. You'll notice that the reward quantity is limited to 30, and that's why. When those are all spoken for, there will be no more!
Risks and challenges
The SBC6120 is a mature product, and many hundreds have been built and sold. Unfortunately many of the parts are either custom made or special order, and when the demand dropped off it became uneconomical to continue stocking them. I've checked with the suppliers and all the necessary parts are still available (although prices have gone up!), so if we can get enough people together at one time then we can order another batch.
The PC boards are fabricated by e-teknet (www.e-teknet.com), the same organization that did the PCBs for the last several runs of the SBC6120. I've verified that they still have the artwork and their current pricing - no problem there. Turnaround is 3 weeks.
The faceplates are fabricated by MSCarita (www.mscarita.com), the same organization that's done them since the beginning. I've verified that they also still have the artwork and confirmed their current pricing. It only actually takes a few days to manufacture 30 faceplates, but turnaround will depend on where we fall in their press schedule. I don't expect it to take longer than the PCBs.
The shadow masks are custom machined by fliptronics (www.fliptronics.com) and I've verified with the owner that he's available to make more. It takes about 45 minutes on the mill to make each one so this project will take a week of solid machine time, but it's available.
The switches are supplied by NKK and I've verified with their warehouse in AZ that sufficient quantities are on hand in the US. There may be an issue with the paddle colors - we may have to take black instead of white - but that's the only concern.
The CPU chips I have in stock, and the remaining parts (e.g. GALs, EPROMs) are easily available, common, items. Based on past experience I expect most of the units sold to be kits, so there is no assembly issue. For those who do buy assembled units, I'll either do it myself if the quantity is small, or hire it out. This is Silicon Valley, after all, and I know several out of work electronics technicians who have more than enough skill and equipment to do the job.
The major risk in this project is simply that there may not be enough people who want one to make it feasible to produce more. That's why Kickstarter "all or nothing" model is the ideal vehicle for funding.Learn about accountability on Kickstarter
The only two pledge levels that mean anything in terms of rewards are $599 for the partial kit and $999 for an assembled unit. Any other pledge is appreciated but you will still receive the same reward.
Kickstarter prohibits offering multiple quantities of rewards for a single pledge, so there is no way to buy more than one. A pledge of $1198, for example, only gets you one assembled unit - it won't get you two partial kits. Sorry - it's Kickstarter's rule, not mine.
Sales tax is due for California residents, but Kickstarter has no mechanism for calculating or assessing this. If you live in California, I ask that you add 8.625% (that's about $51 on the partial kit) to cover that. If you don't live in California then don't worry - it's not an issue for you.
Just select the reward and pledge $999 instead of $599. You'll get an assembled unit. Why so complicated? The problem is that no more than 30 units, total, of both kinds are available. Kickstarter has no way to put a combined quantity limit on separate rewards, and hence there can be only one reward.
At the moment I can only offer shipping to USA addresses. If you live overseas, don't pledge unless you can give me a USA address for shipping.
Yes, as long as you can provide a USA shipping address that's fine with me. Keep in mind that if your friend or forwarder lives in California you're still subject to sales tax and you should include that in your pledge.
Be aware that the assembled units come with a 120V 60Hz power supply, however if you tell me that you're exporting it I'll include a world standard power supply instead. You'll need to supply a local power cord and/or plug adapter.
Also keep in mind that the assembled units contain lead in the solder, are not RoHS compliant and thus are not legal for import into the EU.
The SBC6120 has a standard 40 pin parallel IDE/ATA interface. When it was originally designed the SBC6120 was intended to be used with a 2-1/2" laptop IDE drive, and there are mounting holes on the back of the front panel to accomodate that. These days most people use either a CompactFlash card with a passive CF/IDE adapter, or an IDE SSD drive.
Capacity is not an issue - disk drives in the PDP8 days were 1 or 2Mb at most. One Gb or even 512Mb is a vast amount of space by PDP8 standards that you'll never be able to fill up. The SBC6120 ROM BIOS can't address drives larger than 4Gb - you can still use larger drives, but the extra space is just wasted.
The SBC6120 has an internal switching regulator that's designed to work with a 9-12V DC unregulated input. The SBC6120 and FP6120 alone use about 3-4W but the total power depends on the disk drive you install. With a CF or SSD drive, 5W is plenty. With a 12V input, that's about 1/2 A.
5V 1A regulated DC wall warts are common place these days and it's trivial to adapt the SBC6120 to work directly with a 5V input.
The assembled versions come with a USA specification (120V 60Hz) power supply.
The faceplate is about 15" wide and 8" tall and, with the PCBs attached, the whole thing is about 1-1/2" deep. It's about 75% scale when compared to a real PDP-8/E. That's just comparing the linear dimensions of the faceplate, of course, the depth and weight and power are vastly less when compared to a real PDP8.
The SBC6120 is thin enough that a normal picture frame works well as an enclosure. After you've built it, take it to an art supply store and ask them to make up a frame.
Join the Spare Time Gizmos Yahoo group, http://groups.yahoo.com/group/Sparetimegizmos/. If more SBC6120s, or any other Gizmo, is offered in the future it'll be announced here.
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