FAQ
From Spare Time Gizmos' Wiki
[edit] Manuals and Documentation
[edit] Where are the manuals?
- Except for the differences listed in Overview, the SBC6120-RC is functionally identical to the SBC6120. The -RC uses the same firmware, has the same ROM monitor commands, runs OS/8 and uses the same OS/8 device drivers, and has the same switches and lights on the front panel. For more information about the SBC6120-Rc you should read the SBC6120 manuals,
[edit] Disks and Mass Storage
[edit] No disk drive? Do you want me to toggle in my programs everytime ??
- There's a non-volatile, battery backed up, RAM disk built into the SBC6120-RC. It's software compatible with the RAM disk option for the original SBC6120 and can store up to 1MW (that's 1 million 12 bit words).
[edit] Only 1MW for the RAMdisk? That's not enough!
- Trust me, it's plenty. 1MW is 4096 OS/8 disk blocks, which is as big as any single OS?8 device can be. OS/8 would happily run on a dual RX01 floppy disk system, and the SBC6120-RC RAMdisk is as big as eight floppy diskettes.
[edit] How do I load a disk image into the RAMdisk?
- By downloading the disk image over the serial port, using the same BTS6120 ROM monitor image download functions as the original SBC6120. See this FAQ, "Where are the manuals?"
[edit] Download over the serial port? That'll take forever!
- It takes a couple of hours, but you only have to do it once. Start it up, go out and have dinner, and it'll be done when you get back.
[edit] Can't I plug an ATA/IDE disk into J5?? It has the right number of pins...
- Absolutely not! The SBC6120-RC has no IDE/ATA port and J5 is most certainly not wired for one. If you try to plug a disk or CF card into J5, it'll never work and you'll probably fry something. If you want to know more, see "What's J5 for??".
[edit] Why does my 512kW SBC6120-RC says "448K memory" when it boots?
- BTS6120 is reporting the size of the RAM disk, not the total memory. The HD6120 always reserves 32kW for main memory and 32kW for CP memory, so 512kW minus 64kW gives 448kW and 1MW minus 64kW is 960kW.
[edit] Terminals and Serial Ports
[edit] I get output on my terminal but the input doesn't work...
- If you aren't using the VT6, be sure you installed the jumper at D2 as directed in the assembly instructions. If you are using the VT6, be sure you installed the additional parts, especially D2, D3 and R6.
[edit] If I have the VT6, can I use the DB9/KL8E port for something else?
- No. The VT6 uses the same KL8 console port as any other terminal would - the VT6 just bolts onto the SBC6120-RC motherboard. You can, however, still attach the DB9 port to a PC and use it to download disk images even if you are using the VT6, but that's a special case. Except for that, if you're using the VT6 you can't use the DB9 serial port.
[edit] Construction and Parts
[edit] Some parts seem to be missing from my PCB!
- R3, R4, R5 and J5 are never used and should not be installed. J2, J4, R6, D2 and D3 are used only if the VT6 is also installed. U10 and U11 and the associated bypass capacitors are used only when the memory is expanded to 1MW. The SBC6120-RC can easily run OS/8 (DEC's disk operating system for the PDP-8) using the same RAM disk device driver as the SBC6120.
[edit] What's J5 for??
- The original purpose was to make it easy for me to plug in a Logic Analyzer while I was debugging the initial design. You could always use it for the same if you had a problem to debug. Many people will ask "Couldn't it be used for an expansion board?" - the answer is "possibly". Most or all of the necessary interface signals are there and a clever person could probably work something out, but at the present time Spare Time Gizmos has no plans to offer expansion cards for the SBC6120-RC.
[edit] Other Questions
[edit] Are you planning any expansion boards for the SBC6120-RC?
- No. The SBC6120 specifically lacks any bus or expansion connector, and it's intended to be a self contained, non-expandable, system.
[edit] Are you from Massachusetts ? It says "Boston" on my PC board...
- In this instance Boston is a "who", not a "where". Boston participated in the design reviews (he liked to sleep under the workbench) and I thought he deserved credit for his efforts. And yes, Boston (the city this time) was also the home of Digital Equipment Corporation. Unless you're one of those conspiracy theorists, it's just a coincidence.
