On 10/4/20 10:51 PM, J. David Bryan via cctech wrote: > On Sunday, October 4, 2020 at 16:00, Chuck Guzis via cctalk wrote: > >> A 16MB tape block is impossibly large in any case. > > The HP 3000 mag tape diagnostic attempts to write a single record from BOT > to EOT, which unfortunately fails under simulation due to the 16 MB > limitation. In hindsight, it would have been better to accommodate record > lengths corresponding to the highest density and longest reel length, which > I think would need 28 bits. Four bits for metadata identifier would still > have been be good enough, and one of those should have been dedicated to > "private data" that would appear invisible to programs running under > simulation (and could be used to include information about the tape image > with the tape image).
That's interesting. Looking at my own code for .TAP files, I see the following: #define TAP_FILEMARK 0x0 // 0 = filemark #define TAP_EOM 0xffffffff // -1 = end of medium #define TAP_ERASE_GAP 0xfffffffe // -2 = erase gap #define TAP_ERROR_FLAG 0x80000000 // error flag bit #define TAP_LENGTH_MASK 0x00ffffff // mask for length So increasing the mask for block length wouldn't seem to be a problem, assuming that SIMH could support it. There may be other high-order bit meanings assigned, but I've not run into them. --Chuck
