[cctalk] Re: New TU56 Tape Images Available for simH use

[Paul Koning via cctalk]

> On Aug 1, 2026, at 8:42 PM, David Gesswein via cctalk <cctalk@classiccmp.org> 
> wrote:
> 
> 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.

So will RT-11 FILEX, which from what ABC told me recovers the upper 2 bits in 
each word by watching the CSR as the data DMA is underway, rather than doing 
read-all.  I forgot why he did it that way.

        paul