TU58 tape issues - test-drb@ccmp.vtda.org

jhfinedp3k＠compsys.to

27 May 27 May

10:02 a.m.

blstuart at bellsouth.net wrote:

So I decided to write a TU58 emulator for my 6809 SBC to serve "tapes" from an SD card. So far, I've only implemented a first version of the read side. It seems to work on an XXDP image I found online. However, when I try to boot an RT-11 tape image, I get: @1000G?BOOT-W-Error reading handler ?BOOT-W-Error reading handler ... ?BOOT-W-Error reading handler RT-11SJ V04.00A ?BOOT-W-Invalid or missing TT.SYS ?KMON-U-Overlay read error . .SHOW ?KMON-U-Overlay read error Any ideas on what might be causing this? I've dug up the old rtpip code and gotten it partially working in a more current environment, and it seems to be happy with the tape images I have. I've had this happen on two tape images. Also the original tapes from which these images were made are ones that I've booted from (after I made the tape images), albeit over 20 years ago. So it looks like either something strange in my tape images or something in my emulator that works to load the secondary boot, but fails for loading some other parts of the tape.

My first reaction is that the most likely problem is the RT-11 image on the emulated TU-58. If you can read the files on that image, there may be nothing wrong with the emulation. What may be the problem is that you RT-11 image on the emulated TU-58 tape is missing the file TT.SYS and is giving those error messages as a result. Can you obtain another RT-11 distribution and copy it to the emulated TU-58 tape image? After you do that, you will need to: COPY/BOOT DD0:RT11SJ.SYS DD0: to make the emulated TU_58 tape image hardware bootable. Otherwise, if that is not the problem, additional information will be needed. Jerome Fine

Reply

jhfinedp3k＠compsys.to

10:17 a.m.

...

blstuart at bellsouth.net wrote:

...

So I decided to write a TU58 emulator for my 6809 SBC to serve "tapes" from an SD card. So far, I've only implemented a first version of the read side. It seems to work on an XXDP image I found online. However, when I try to boot an RT-11 tape image, I get: @1000G?BOOT-W-Error reading handler ?BOOT-W-Error reading handler ... ?BOOT-W-Error reading handler RT-11SJ V04.00A ?BOOT-W-Invalid or missing TT.SYS ?KMON-U-Overlay read error . .SHOW ?KMON-U-Overlay read error Any ideas on what might be causing this? I've dug up the old rtpip code and gotten it partially working in a more current environment, and it seems to be happy with the tape images I have. I've had this happen on two tape images. Also the original tapes from which these images were made are ones that I've booted from (after I made the tape images), albeit over 20 years ago. So it looks like either something strange in my tape images or something in my emulator that works to load the secondary boot, but fails for loading some other parts of the tape.

My first reaction is that the most likely problem is the RT-11 image on the emulated TU-58. If you can read the files on that image, there may be nothing wrong with the emulation. What may be the problem is that you RT-11 image on the emulated TU-58 tape is missing the file TT.SYS and is giving those error messages as a result. Can you obtain another RT-11 distribution and copy it to the emulated TU-58 tape image? After you do that, you will need to: COPY/BOOT DD0:RT11SJ.SYS DD0: to make the emulated TU_58 tape image hardware bootable. Otherwise, if that is not the problem, additional information will be needed. Jerome Fine

Reply

ajp166＠verizon.net

1:10 p.m.

One area where people get burnt with TU58 (real) is that when it sends data the receiving system better be able to keep up for the whole packet! That sometimes means the data rate must be lowered from 38,400 to whatever works for the system in question. For example PDP-11/44s had problems using the console port at more than 9600! Allison On 05/29/2013 11:33 AM, Brian L. Stuart wrote:

...

My first reaction is that the most likely problem is the RT-11 image on the emulated TU-58.

Thanks for the suggestions. As an update, I've done a little more investigating. I ended up installing tu58em and verifying that the tape image was good and that I could boot using tu58em. Last night, I did a dump of tu58em's debugging output and manually issued the same set of reads to my emulator. I verified that all the packets had the same checksums, the same first few and last few data bytes, and that the end packets all matched. So it's looking like it's coming down to either something related to timing or there's something I'm not doing right with respect to breaks or inits. In looking over the RT-11 boot code, I'm now pretty sure that things break down when it shifts from using the boot version of read to the read interface the monitor uses. I"m thinking my next step is to interpose a machine with 2 serial ports and record the whole protocol when it fails and see if that shows anything. BLS

Reply

fraveydank＠gmail.com

11:14 p.m.

On Jun 14, 2013, at 10:18 PM, blstuart at bellsouth.net wrote:

...

One area where people get burnt with TU58 (real) is that when it sends data the receiving system better be able to keep up for the whole packet! That sometimes means the data rate must be lowered from 38,400 to whatever works for the system in question. For example PDP-11/44s had problems using the console port at more than 9600!

My read issues did turn out to be what appears to have been sending too fast. I added a few strategic delays and that seems to have taken care of things. Last weekend, I also got the writes sorted out. So my little 11/2 with an MXV-11 in a BA-11VA case can once again boot RT-11. It's even managed to tickle a few very old brain cells that stored some of the teco I used to know. :) There's a part of me that can't resist trying out a sysgen to see just how painful it'll be.

Well, you've got all weekend. - Dave

Reply