Roger Holmes wrote: MOST????? STANDARD????? Rubbish! IBM 7094 - 36 bits. ICT 1301 - 48 bits. CDC 6600/7600 60 (or was it 64?) bits. CDC SC17 (not sure exact era) - 16 bits. Elliott 903/920B/905/920C/920ATC - 18 bits. Many of the BCD machines used 4 bit words I believe. Mid 60s ICL 1900 - 24 bits. What used 40 bits? Tell us more please. Microcoded or 'Extra code' ? Actual physical memory, access my DMA from the device or just memory mapped I/O ? ----------------- Billy replies: This was a serial machine using a magnetic drum for memory. So the registers and memory were all bit serial and on the drum. I/O was accomplish by moving data from one line to another. The logic at each end of the line was in peripheral but the bits were on the drum. So it really doesn't fit the standard definition of memory mapped I/O, though that is the closest description. There were no channels per se. Al has just posted most of the G-15 manuals. Have a look. It certainly qualifies for the weirdest machine I ever worked on. ---------------- Roger Holmes: Remember? I am restoring/maintaining an ICT 1301 which has individual Germanium transistors, wire-OR, four and gates to a PCB, one flip- flop one a PCB, a clock derived from the timing track of the last addressed drum store, a core store unit weighing half a ton an stores just 2000 x 48 bit words (plus 2000 x 2 parity bits). Its got Ampex TM4 mag tape drives (not industry standard 7 or 9 track, these are ten track units with hubs the same design as professional audio tapes and the 2 and 3 inch wide video tapes once used by TV broadcasters). [Snip] --------------------- Billy: I salute you. I wish more people on this list had your energy and love of old metal and were restoring it. I enjoy hearing about your efforts. I'm also working on a germanium transistor wired-AND core memory machine. It used TM2's not TM4's. And I've been unable to find any tape units. Did find the original card reader, a modified Burroughs. Still, I consider what you are doing to be the true goal of classic computers. I read, enjoy and participate with the microprocessor based list threads. But my real love is in truly "classic" computers like yours. ---------------- Roger Holmes: Indeed. And some of them almost make you cry because so much more could have been done with the same amount of electonics. My machine has been modified to implement an index instruction. Previously all indexing and indirection had to be done by program modification, and even now subroutine return is done that way (see my previous e-mail). I have one machine in 'conserved' state, unmolested, unrepaired non- runner, and one with extra tweeks and darn right mass rewiring which runs and I can't stop thinking about how it could be improved, yet somehow manage to stop myself doing so. There are so many gaps in the instruction code and spare bits in the instructions etc. The only modification I am working on plugs into an extension port lashed up by a previous owner. This is to capture the data from the machine onto modern media. May replace with an RS232 interface later to drive a teletype and/or pen plotter, and/or a parallel inteface for a Friden Flexowriter. [sni] Roger Holmes. Classic computer collector, classic car collector, machine tool collector/user (for the prior mentioned hobbies), and for a job, programmer of CAD and graphic software and printer/plotter drivers for Apple computers.