I couldn't find any information on the Prisma workstation on the 'net so I thought I would put some information here in case anyone else comes across one of these boxes. The following is based on some documentation that came with the boards together with my experiences porting Minix to a model 700 workstation with the enhanced controller and a 33MHz 68020.
There was a later model, the Prisma 40, which used a 68040 but I have no documentation on it at all. As of October 2000, however, I have started investigating the 040 model with the ultimate aim of a full Linux-68k port. I will post the hardware details here as I find them.
The basic hardware spec of the model 700 workstation is:
Width 540mm / 21.25in Height 115mm / 4.5in Depth 425mm / 16.75in Weight 12.6kg / 28lb Processor CPU 68020 at 16,20,25 or 33MHz FPU 68881 Memory 4MB Exp. memory 4MB RS-232 ports 3 (tablet/mouse, joystick, data terminal) Video Output RGB via 3 BNC sockets, sync on green Resolution 1280 x 1024 Planes 9 (8 bits for colour plus a 1-bit overlay) Vert. sync 60Hz Horiz. sync 63.9KHz Dot clock 110MHz Network Ethernet AUI or BNC (on-board transceiver)
The basic workstation comprises the chassis, with power supply and fans, and two large circuit boards. The "Graphics Controller", which is the main CPU card, and the "Video Buffer", which contains all the video memory and display logic. The two boards are linked by a ribbon cable. The CPU card is also socketed to take an optional daughter-card for RAM expansion.
The video buffer is not memory mapped, instead it is accessed via a number of 32-bit registers mapped into the address space of the controller board. The video buffer has hardware assistance for line drawing only, doing anything else with it is hard work
Note that the original workstations used an external terminal for their console display, this connected to the 'data terminal' port and there was no keyboard socket (I am guessing a bit here, I haven't seen one). Later models, such as mine, have an extra keyboard interface board which is mounted underneath the controller board and is connected directly to its terminal port There is a PC-style 5-pin DIN socket at the rear for the keyboard and the 'data terminal' port is unused.
There have been a number of revisions of the boards but unfortunately I do not have any detailed information about what the differences are. One difference I do know about is that you need an enhanced controller to work with the keyboard interface. The chassis and boards that I have seen are:
Chassis 33566-002 Prisma chassis with PC keyboard 33720-002 Prisma 40 chassis (68040 board) Graphics Controller 33254-001 Graphics Controller 33254-002 " " 33471-002 Enhanced Graphics Controller 33471-004 " " " 33676-001 Graphics Controller/40 Video buffer 33249-001 RAM on SIMM-like sub-assemblies 33500-001 RAM in ZIP chips 33602-001 Used with the Graphics Controller/40 Keyboard Interface 33584-001 4MB RAM expansion 33369-001
The standard and enhanced graphics controllers both used the same chip sets.
CPU MC68020 at 16,20,25 or 33MHz FPU MC68881 at 16,20,25 or 33MHz DMA MC68440 dual channel DMA controller ROM 128KB of EPROM using 2 x 27C512 SRAM 128KB of static RAM using 4 x M5M5256AP DRAM 4MB of DRAM expandable to 8MB using daughter card NVRAM TS48T02 2KB NVRAM plus real time clock MFP TS68901 for the console (also timers and interrupts) SIO TS68564 for the mouse and joystick SCSI WD33C93 Ethernet AMD7990 LANCE