[Simh] EXT :Re: TU58 device for PDP-11s

[Don North]

On 6/26/2015 12:10 PM, Timothe Litt wrote:
>
> On 26-Jun-15 13:43, Hittner, David T (IS) wrote:
>>
>> What PDP-11 used TU58’s, and what controller did the drive connect to?
>>
>> Dave
>>
> 11/23, 11/44, VT103, HSC50 -- among others.
>
> Host: Any RS232/423 (dumb) interface, e.g. DL(V)11, MXV11.  9600 - 38400 BPS 
> using a packet protocol (RSP, IIRC) with XON/XOFF flow control
>
> The drive itself has an embedded 8085 CPU that is the real controller.  It's 
> not terribly smart.
>
> The protocol is roughly similar to MSCP (lighter-weight); the tape is 
> block-addressable, normally the 512 byte DEC standard block, although there's 
> a 128 byte record mode for dealing with buffering/comm issues.  Normally the 
> controller assembles 4 records to make a block.  Cartridge is formatted with 
> 512 blocks of 512 bytes each (0.25 MB).
>
> http://bitsavers.trailing-edge.com/pdf/dec/dectape/tu58/ has the docs.
>

As indicated the physical TU58 controller connects to a plain serial line 
interface on the PDP-11. A DL11-W works fine for example. It uses just RS232 TXD 
and RXD, no other sideband signals. The TU58 serial interface wants to be a 
776500/300 on a PDP-11 for software compatibility.

The DEC DL11 serial boards run at 9600baud (normally the fastest) which works 
for the TU58 emulation, but is a bit slow. Boots XXDP diag in about 2 minutes.
The PDP-11/44 has an integrated TU58 serial port that can run at 38.4Kbaud, 
which makes it a more usable configuration.
It is possible to (reversibly) modify a DL11-W to run at 115.2Kb (replace UART 
chip, bypass baud divider, new oscillator) that runs very nicely on a PDP-11/34, 
for example. Boots XXDP diag in about 15 seconds.

There is a command line program for Windows/CYGWIN, MacOSX, and Linux that 
emulates a physical TU58 drive controller, up to eight units.
The source and Windows executables are now hosted here: 
https://github.com/AK6DN/tu58em

I also have a web page that has a number of useful XXDP diagnostic tape images 
for various PDP-11 systems: https://ak6dn.dyndns.org/PDP-11/TU58/

I tried early on to configure SIMH with a DL11-W style serial port and connect 
TU58EM running as a separate process and got it to work, sometimes.
This was a long while ago (a few years) and I have not tried it since.

It probably would not be a big programming project to build a direct TU58 add in 
controller into SIMH. The documentation all exists on bitsavers.

Note that booting a physical VAX-730 requires a functional TU58 in the system 
(either real tape drive or emulated tape drive via TU58EM).
Mark Blair just recently revived his 11/730 and got it to run diagnostics and 
boot VMS using a slightly modified variation of TU58EM running on MacOSX.
The VCF forum: 
http://www.vintage-computer.com/vcforum/showthread.php?36113-Problems-using-tu58em-with-VAX-11-725-VAX-11-730
describes all this.

Don


















> This communication may not represent my employer's views,
> if any, on the matters discussed.
>
>> *From:*Simh [mailto:simh-bounces at trailing-edge.com] *On Behalf Of *Bill 
>> Cunningham
>> *Sent:* Friday, June 26, 2015 1:14 PM
>> *To:* Hans-Ulrich Hölscher; simh at trailing-edge.com
>> *Subject:* EXT :Re: [Simh] TU58 device for PDP-11s
>>
>>     ----- Original Message -----
>>
>>     *From:*Hans-Ulrich Hölscher <mailto:hoelscher-kirchbrak at freenet.de>
>>
>>     *To:*simh at trailing-edge.com <mailto:simh at trailing-edge.com>
>>
>>     *Sent:*Friday, June 26, 2015 12:56 PM
>>
>>     *Subject:*[Simh] TU58 device for PDP-11s
>>
>>     Am I right that there is currently no TU58 device available for the
>>     PDP-11 series of computers?
>>
>>     If so, would someone be so kind as to implement it?
>>
>>     Thanks in advance to all programmers who ponder on evetually doing it!
>>
>>     Regards,
>>
>>     Ulli
>>
>>
>>     I don't know about simh, but there are several simulators out there.
>>     There is something for linux too. But it sounds like a worthy cause.
>>
>>     Bill
>>
>>
>
>
>
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