Wherein I write about things that interest me….

New run of the Sparetime Gizmos SBC6120

I have been following the Sparetime Gizmos Yahoo group since I first heard of the SBC6120, basically a single-board computer reproduction of the DEC PBP8. It was based on the Harris Semiconductors HD6120, which is basically a PDP8 CPU on a single chip, as opposed to multiple flip-chip boards. So, in essence, turning this


into this…


However, the HD6120 is in very short supply, and expensive, and the Sparetime Gizmos board is out of production, and Bob Anderson has said that he will not be doing any future runs. ;

Recently, there was a bit of activity on the Sparetime Gizmos Yahoo Group when Andrew Bunghan, the administrator of RetroBrew Computers;posted an investigation of interest to see how many people might be interested in a partial kit to build a Single Board PDP8, based on a newly fabricated PCB, using a cheaper 2 layer process, and a kit of the harder to acquire silicon. The prices were very reasonable… much less than the original unit, so I immediately signed up. A few months later, I got a follow-up email from Andrew requesting payment if I was still interested. I paid straight away, and within a couple of days had a tracking number, and a further 4 days later, had the package. The contents consisted of the PCB, the HD6120 CPU, some EPROMS and various other glue.


The project pages include a BOM generator spreadsheet, but the vendor of choice is Mouser, who are unreasonably expensive for shipping to Ireland, so I took the time to generate an equivalent BOM for Farnell, who ship to Ireland free. The component costs are very reasonable at Farnell also, often competing with, and beating the likes of Mouser and Digikey. The Farnell BOM is almost complete, apart from an oscillator, a polyfuse and a couple of connectors. I am making it available for download here.

I have ordered the BOM, and will be posting a build-log as construction progresses.