From: Noel Chiappa Sent: Monday, October 17, 2016 7:21 PM >> From: Ian S. King
>>> Does anyone know anything about the status of the plans to open-source >>> it? >> I've made some inquries, stay tuned.... > OK, thanks! >>> Can you briefly describe what it was? > I'm still curious about what it was: was it a stand-alone board with a > separate power supply, or did it plug into some sort of backplane? Did it > use something like SD cards for storage? And what was the MASSBUS > connection like: a set of 3 Berg headers into which one plugged the flat > cables, or was there some oddball connector that wound up connected to a > standard MASSBUS connector? There have been 2 generations of Massbus Disk Emulator (MDE) at LCM. The one of which people have seen pictures was the first generation, created when there were only 2 people working on the collection which became the museum years later. This was a breadboarded prototype which supported 4 emulated RP06 disks, represented by directories of track files, each representing 20 sectors of 128 36-bit words. These mimicked the physical layout of the data on disk, where each 18 bits of data has an associated parity bit; this was stored as 3 8-bit bytes (3rd byte being 2 data + overall parity). The MDE itself was made up of a Rabbit and 3 PICs; the driver/receiver portion of the board terminated the Massbus. Standard Massbus cables connected it to the 2065 running Tops-10. Data was transferred via FTP over a 100baseT crossover cable connected to a Slackware server; the Rabbit was able to keep up with 4 drives at this speed, but a 5th drive (MDE could in theory represent an entire 8-drive string) would cause data dropouts on all units. Various improvements were attempted on this (work with Unibus on a 2020, for example), but it was never quite stable enough. MDE 2.0 was created by a different engineer with lots of resources thrown at him. He replaced the Rabbit and PICs with a Mesa 5i22 Anything I/O card (includes a Xilinx Spartan-III FPGA) that plugs directly into the PCI bus in a server-class X86-64 box, and used a revision of a separate driver/receiver card designed for MDE 1.0 to connect to the Massbus, still via standard cables. An outside contractor wrote a control program for the PC side which runs under Windows 2008/2012 Server. MDE 2.0 supports SimH-format RP07 and RP06 disk drive images. There is also a variant for tape drive emulation called the MTE, which reads and writes to SimH-format tape files. We currently run the DECSYSTEM-2065 (public Tops-10 v7.04), DECsystem-1070 (public Tops-10 v6.03A), PDP-11/70 (public Unix v7), and DECSYSTEM-1095 (under development: WAITS operating system from Stanford Artificial Intelligence Laboratory) using MDEs. The two KL-10 systems also have an MTE apiece; we haven't needed tape service on the KI-10 or the 11/70 so far. Rich Rich Alderson Vintage Computing Sr. Systems Engineer Living Computer Museum 2245 1st Avenue S Seattle, WA 98134 mailto:ri...@livingcomputermuseum.org http://www.LivingComputerMuseum.org/