Well here we are again at the end of RetroChallenge and as usual I've done very little.
Here are the things I've actually managed to do over the month...
I tried installing the VideoNula board at the last ABUG meeting. Daniel kindly unsoldered the old video chip and added the socket to the board ready for the VideoNula to be installed.
Upon taking it out of its box I found that it was missing a pin. Luckily I managed to see the creator of this great bit of kit at the Wakefield show and managed to get a new one sorted.
Upon installing the VideoNula board I found that my PiTubeDirect overlapped into the space where the new board sat. To sort this I had to order some longer pin extensions which I added to the current pins to raise it above the VideNula board so that I can have both fitted.
Here they are both playing nicely together. The long board with a Pi Zero attached to it is the PiTubeDirect. Underneath that is the VideoNula board replacing the original video ULA chip.
The VideoNula allows for the palette to be selected from 4096 colours and supports hardware scrolling and various other extras.
The PiTubeDirect is a board that connects a Pi Zero to the Acorn tube interface (by running special software on the Pi) and emulates various co-processors that you could get for use with the BBC.
By running a certain command you can change to various different setups.
The co-processors supported are...
65C102 running at 274Mhz (nearly 100 times as fast as the actual hardware co-processor)
65C102 running at 3Mhz (same as the original co-processor for compatibility)
Native ARM (this runs on the actual Pi at 1Ghz)
By switching these on you can run code on a different platform and the BBC handles all IO.
Ethernet / MultiOS
I re-installed the Ethernet adapter from Sprow. This is a great item that sits in the machines Econet slow and provides modern networking. It provides the LanManFS filing system which lets you use a Windows share as a filesystem on the BBC.
Below the Ethernet card is the MultiOS board. This allows me to select various different OS versions by turning a switch on the back of the machine. I normally run in OS 3.5 but you can run the basic BBC 1.2 OS which allows for maximum compatibility. I need to create some OS images and get them burnt to the ROM so that I can change from the DataCentre (which requires a patched OS) to the BeebSCSI & GoTek floppy emulator (which works with the standard OS).
BeebSCI and VFS Adapter
I've already got a few of the BeebSCSI mini boards that allow the use of an SD card to provide a SCSI file system which is accessible from ADFS.
The DataCentre provides a similar thing but requires a patched version of ADFS to handle IDE drives. BeebSCSI works without needing to change anything on the machine.
As part of this project you can emulate a VFS drive (the laserdisc filing system that the Domesday project used). The final objective is to emulate the entire Domesday system without needing the laserdiscs or SCSI interface.
I started working out where the other interfaces I have will live inside the case.
Here are the DataCentre, BeebOPL (music synth) and the BeebSCSI mini. All run from the 1Mhz bus so I need to be able to switch between the DataCentre and the BeebSCSI easily.
I've got all the cables and connections ready just need to find the time to actually measure and make the cables to size.
My other external Co-Pro emulator, this is a different project but related to the PiTubeDirect.
This however uses a CPLD to do the heavy lifting.
It can emulate the following...
65C102 (at various speeds)
Z80 (at various speeds)
I am looking to attach this to the external Tube port so that I can switch between the internal PiTubeDirect and this.
Battery Backed RAM Cartridge
I bought this a while ago and it allows for loading of 2 ROM images which are stored in battery backed RAM so can be re-programmed from the machine. By changing the switches you get 4 different banks of 2 ROM slots. You can also use a real ROM and activate that by changing a switch.
This is my external DataCentre.
It will be replaced by the internal one on this machine once the cabling is complete.
The unit allows you to load disk images from a USB stick and provides 2 IDE hard disk slots on the back.
Here is the re-assembled machine. Next stop a new paint job.
Anyway that's my (pretty lame) effort this time round.
See you back in the Autumn.