The PDP-8 tapes are 12 bit words in low bits of 16 bit word. The other tapes are 18 bits in low bits of 32 bit word. Both little endian. SIMH pdp-8 simulator knows about these formats.
The images only contain the data words from the tape blocks. PDP-8 tapes are 129 word per block and normally 1474 blocks. The 18 bit tapes are 256 words per block and normally 578 blocks. PDP-8 PIP10 will give a directory of the PDP-10 tape. Note in the .zip file are files with 16 in the filename. Those have the upper 2 zero bytes removed to allow easier viewing of strings in the file. I don't know if anything supports that format. On some of the other posts > Did he use read-all mode to read the raw tape structure? Or is this something > lower level still, without using a TC11 controller? > I have used my TD8E PDP-8 controller to read tapes. I tried inverting the timing track for reading LINCtapes with the PDP8 but it was hit or miss so I created the analog digitizer with software decode. It hooks directly to the head cable. FYI: My software archive. Some others have read and sent to me. https://www.pdp8online.com/images/index.shtml > Your comment about 00 tracks does not appear correct. > This was comment on viewing the data files in a hex editor. Its is the number of bits actually used 16 or 18 in the 32 bit word. Tracks wasn't the best word choice. The reader is a bunch of instrument amps that amplify to levels usable by Saleae logic 16 pro which has analog digitization mode and way too many times repurposed code to decode it. Doesn't look like I have put it online probably because the code is embarrassing but ok with giving it away if someone has use for it. If I missed question ask again. On Fri, Jul 31, 2026 at 09:21:19PM -0400, Rich Alderson wrote: > Bill Degnan via cctalk <[email protected]> writes: > > > https://www.vintagecomputer.net/browse_thread.cfm?id=833 > > > New TU56 Tape Images Available for simH use. I will post updates on this > > thread, but if anyone is interested in messing around with the images > > using simH, feel free to download and explore/use. > > Just out of curiosity, what is the internal format of these images? > Most especially, what is the internal format of the "18 bit" file? > > They look to be something more clever than little endian 32 bit > integers, where "clever" is not necessarily complimentary. > > -- > Rich Alderson [email protected] > Audendum est, et veritas investiganda; quam etiamsi non assequamur, > omnino tamen proprius, quam nunc sumus, ad eam perveniemus. > --Galen > > ------------------------------
