VAX 11/750 rescued, alas...

J Blaser oldcpu2 at
Mon Oct 8 17:40:48 CDT 2007

Ethan Dicks wrote:
>> trying to use them in the VAX (eventually)?  Is it just a standard
>> serial connection coming off of the drive, like the desktop TU58
>> subsystems, or is it something lower level?
> Electrically, it's a standard serial interface, but I think there
> might be an odd cable because it's an 11/750-internal cable.  Nothing
> insurmountable with a willingness to make a cable adapater.
> Yes, you could use an 11/23+, or even a modern machine running DOS or
> UNIX and one of the several TU-58-slurping programs out there.

This is useful to know.  I've only had experience using Will Kranz' TU58 
emulator on a PC running against my PDP-11/23+, but if it's just a cable 
then it'll be pretty easy to get it connected to the RT-11 environment 
and capture the images.  A simple serial cable is no sweat.

In the last couple of days I've had a chance to poke around inside and 
extract the carts.  Looks like there are four altogether (I thought 
there were six), three of which look to be DEC original carts for bits 
of FORTRAN 4.4, and the fourth is some kind of driver/diagnostic tape 
for the Systems Industries 9700 board, looks like.

> I personally use a dual TU58 from an 11/725 and a PC to read my carts.
>  I forget, at the moment, which program I'm using, but it's one of the
> old, standard ones that's been kicking around for years.  I have about
> an 80% success rate with the tapes I've read so far.

Mmmm...  I doubt the four carts that I have are particularly rare, 
someone probably has an image of these already, but I just like to copy 
everything that comes my way.  Who knows?  And based on your success 
rate, if I see similar results, I might get lucky and be able to copy 
the four carts I have, with an imaginary fifth cart making up the 20%  
that are unreadable.  ;-)

> Oh... you could eventually substitute a PC or FLASH-based TU58
> emulator in place of the drive, but in practice, we only ever used our
> TU58 for booting diagnostics or Standalone Backup for OS installs, or
> loading the DEC Microcode patch... come to think of it... the
> Microcode patch (which we started using around VMS 4.6 or 4.7) would
> be an excellent use for a TU58 emulator.  

I'm not too worried about this at the moment, at worst I can use a PC 
running some type of TU58 emulation, but a simple dedicated device might 
come in handy when all of these TU58s start dying off for good, replaced 
roller or not.

> P.S. - as for adding wires to the backplane, any wire-wrap tool should
> suffice, including the manual tool that Radio Shack used to sell
> (looks like a Jeweler's Screwdriver, with a wire-stripper stored in
> the handle).  No unusual tools (beyond ordinary WW tools) are
> required.

Okay, I can probably handle that.  I have a simple WW tool exactly as  
you describe that I occasionally use on DLV11-Js and whatnot, so as long 
as I know what pins to connect, should be doable.  ;-)

> P.P.S - if you are *lucky*, there are plastic alignment blocks on the
> backplane where the cables tap into the off-board I/O area.  If not,

Haven't examined that side of the backplane yet...

> you might want to track down the installation manual for the SI
> 9700/9900.  

So far no luck on bitsaves or manx.  I'm still on the hunt, though...

- Jared

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