Re: DEC weights

[Fritz Mueller via cctech]

> On May 23, 2021, at 9:14 PM, Marc Howard via cctech  
> wrote:
> In my case I'm looking for the weight of an RK05 and full height 19" DEC
> rack.

I have not see these published, but can attest that it is somewhere between 1 
25-yr-old-can-load-in-station-wagon and 1 53-yr-old-can-load-in-station-wagon...

Re: RK11-D "diskless" test ZRKJE0???

[Fritz Mueller via cctech]

> On Jul 9, 2020, at 5:02 PM, Robert Armstrong via cctech 
>  wrote:
> I have an 11/04 with an RK11-D.  I have a couple of RK05s, but I wanted to 
> test the controller before I start working on the drives.  The PDP11 
> Diagnostic Handbook says that ZRKJ?? "checks only the drive-independent logic 
> of the RK11 controller. no drive is needed..."  I assumed that meant it was a 
> diskless test, but now I'm not sure that's true.  Can anyone confirm or deny 
> this?

Hi Robert,

My experience with an RK11-C on a PDP-11/45 is that the drive-independent 
diagnostic does in fact work with no drives attached. For the RK11-C at least, 
it does clever things with maintenance-mode to simulate signaling that would 
source from the drive where necessary.

I know there are some differences between the RK11-C and the RK11-D -- if some 
of these are related to maintenance mode, it could also be that you need to 
verify that the version of the diagnostic you are running is RK11-D (and not 
just RK11-C) aware?

Another possibility is that you should pull the BC11 and add another terminator 
rather than leaving it dangling?

--FritzM.

Re: PDP-11/40 available, Arizona

[Fritz Mueller via cctech]

On 5/10/19 6:42 PM, Adam Thornton via cctech wrote:

I have been invited out to the site tomorrow morning to take an inventory of 
what’s there (I live near the machines).
I imagine that I may well have a lot of photos that I bring to the list and say 
“what is this?”


Standing by to help out!  Go get it, Adam -- (come on, you can _make_ 
room! :-))

Re: advice / suggestion wanted PDP 11/40 only boots XXDP, not RT11

[Fritz Mueller via cctech]

> On Jan 31, 2019, at 12:26 PM, Bill Degnan via cctech  
> wrote:
> 
> My PDP 11/40 suddenly lost it's ability to boot RL02 disks except the XXDP
> disk.  I have two drives, both boot up an XXDP (I have more than one) just
> fine, but any formerly-working RT-11 (v 5, 5.1, 5.3) no longer boots, it
> just hangs.

I'd check things related to interrupts.

My experience has been that XXDP monitors (at least the earlier ones) use 
polling, and can be boot and run even when disk controller interrupts aren't 
working because of this.

--FritzM.

Re: VT52 keyboard question

[Fritz Mueller via cctech]

> On Mon, Mar 13, 2017 at 4:45 PM, Marc Howard via cctech <
> cctech@classiccmp.org> wrote:
> 
>> Hi,
>> 
>> The "2" key on my VT52 is very hard to use.  You've gotta pound it and you
>> might get 2 "2"s for your trouble.

I've a similar key on my VT52 -- will be diving in there sometime soon to check 
it out, but it might take me a little while to get to it...  Will follow-up 
here when I do with whatever I find out.

  --FritzM.

FTGH: iMac G3

[Fritz Mueller]

Hey folks,

Helping my ex clean out her basement, she had a 1999 tray-loading "lime" 
iMac G3 that she no longer wanted.  The machine is complete w/ original 
keyboard, mouse, and power cord.  Boots and runs MacOS 9.2.  CRT is 
arcing occasionally (probably dust around the flyback?)


I'm not a Mac collector, but I scooped it in case anybody here might be 
interested?  Free for pickup in Oakland or Menlo Park CA, or for cost of 
shipping anywhere else.  Drop me a line if interested -- otherwise it'll 
be off to the local ecycler in a week or two!


cheers,
   --FritzM.

Re: Unibus disk controller with modern storage

[Fritz Mueller]

On Oct 19, 2016 6:48 PM, "shad"  wrote

Hello,
I read several posts about Unibus disk interfaces and emulation.
One of my retrocomputing dream is to design an Unibus universal board,
probably based on FPGA because of precise timing requirements,
to emulate one or more disk/tape interfaces, and possibly something more.
The real storage could be based on SD card, so very easy to be moved
to a PC for imaging and data transfer.
Probably a low level emulation would be quite easy, while a more complex
solution (MSCP) could be more difficult.
The board itself wouldn't be cheap at all, because PCB would be big,
and because FPGA aren't cheap either.
Probably it would be anyway cheaper than an MSCP-SCSI, and it would be far
more
flexible.


A good way to go on this might be just a small paddle card with Unibus 
drivers, level conversion, and some shift-register chains, which could 
then be interfaced easily to any number of off-the-shelf FPGA 
prototyping boards (the latter having the advantage of being quite 
cheap, with many integrated peripherals like ethernet, SD slots, USB 
serial, etc. and having tool chain support out of the box).


I've seen a few projects started like this out in the wilds, but none 
seem to have made it past the debug stage.


It would be super useful -- you could emulate all sorts of peripherals 
as well as memory, or you could configure it as a Unibus analyzer, or 
emulate a CPU to debug peripherals.


--FritzM.

Re: Tough to Diagnose issue with PDP 11/40 CPU

[Fritz Mueller]

Hey Bill,

Do you have a KM11 maintenance card?  Guy Sotomayor here sells kits 
and/or assembled boards at 
http://www.shiresoft.com/products/km11/KM11%20Replica.html.  I built one 
up myself based on a layout by Tom Uban at 
http://www.ubanproductions.com/museum.html


The easiest way to get to the bottom of this since you have a nice, 
short, repro case would be to step through the microcode with a KM11 and 
see where it goes awry.  From that point, its fairly easy to come of up 
a list of boards to swap and/or chips to check.


If you want to go to the chip checking stage, you'll need some board 
extenders and a logic probe, they are pretty cheap.  Or you can grab a 
surplus logic analyzer and some DIP clips off eBay if you want to get posh!


I just went through this process with my 11/45, it was pretty educational.

--FritzM.