What are the really unusual or weird computers?

[Roger Holmes]

>
> From: "Mike Hatch" <mike.hatch at mclennan.co.uk>
>
>>  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).
>
> Our SDS9300 had TM4 drives but I don't remember them being 2 and 3  
> inch
> wide, I thought they were 0.5 inch, but then that was 35years ago.

Yes they are half inch. What I meant was that they are not 'industry  
standard' half inch tape with large expanding hubs with the write  
protect ring in a groove in the reel. Instead the centres are much  
smaller, allowing 3200 feet on the same outside diameter spool as a  
2400 foot reel using the same thickness tape (not the ultra thin  
tape). The reels are aluminium, not plastic, their centres have three  
notches which three matching 'fingers' within the hub fit into,  
holding the reel onto the hub. Some TM4s were fitted with small  
expanding hubs (the ones on the Leo and maybe others), but this did  
not fit 'industry standard' reels. The same design of hub is used on  
tapes of quarter inch, half inch, one inch, two inch and three inch,  
maybe other sizes too. I do not mean domestic quarter inch tape  
recorders, these use a simple nut on a stud. The write protect ring  
protrudes from the back of the reel, and three projections on the  
ring fit into three holes in the reel. The tapes themselves have a  
metalised leader which is electrically sensed by the deck. They also  
have a reflective early end of tape marker like later tapes, and I  
think they have a metalised leader at the end of tape, though I've  
never unreeled 3200 feet of tape to find out.