DecServer 550 chassis

Johnny Billquist bqt at
Mon Oct 19 18:19:26 CDT 2015

On 2015-10-19 23:11, jwsmobile wrote:
> On 10/19/2015 12:39 PM, Johnny Billquist wrote:
>> Well, you did ask for "thoughts in the conversion", so I gave you
>> mine. Sorry if you felt they were unhelpful. I just thought the
>> "conversion" was basically a no-work. Programming proms is something I
>> have spent more time than I can count on, and is so routine that I
>> don't even think about it.
> I didn't mean that in disrespect.  The contents of what I posted was on
> the page and I basically needed the binaries and needed some direction
> as to which went where.  I appreciate you taking time to reply, but am
> coming from a lot less capability than you have.  I do a lot of
> computing and the like, but I've purposely not kept up with eprom
> technology to the point that i can't reliably swear I can program them
> right now.
> There are only so many things one can keep up with and eproms were not
> one that was cheap to follow, and I was more into EE type devices anyway.

Well, EPROMs are getting sortof old fashioned nowadays.

> I may need a favor by swapping you some of my eproms (I have a 12" x 12"
> x 12" box of pulls) maybe to get you to make me a set for my board.

Unfortunately all of my stuff in Sweden, while I nowadays live in 
Switzerland. So I could only possibly help out next summer.
But I probably would have some 27256 around.

> I've pulled out probably 500 and returned them to the original owner and
> owe him more.  but I do probably have a lot of the 27xx proms.
> Do you think these are 27C or just straight 27 type eproms, and if so
> what speeds?  That is what I need to know too.

I normally don't care about that. The difference is in how you program 
them, and there are more variations than that. Fortunately my programmer 
knows a whole bunch of them, and also can autodetect the different models.

But once they are programmed, the actual pins are the same, so speed is 
the only possible issue. But I think most of them are 125ns, which is 
fast enough anyway.

I replaced the firmware in some 11/93 boards a few years ago. But I 
think I just reused the existing proms that time.

But I don't have any 11/53 boards, so I can't do that here.


> thanks
> Jim
>>     Johnny
>> On 2015-10-19 20:57, jwsmobile wrote:
>>> On 10/19/2015 10:03 AM, Johnny Billquist wrote:
>>>> Not sure what you expect a "conversion" means. Creating new PROMs
>>>> imply finding actual proms, a prom programmer, the code to program
>>>> into the PROMs, and then just replace the proms on the card.
>>>> Only the last piece will actually require any modification of the
>>>> card, and I would expect them to be socketed anyway, so replacing
>>>> means just removing the old proms, and inserting the new ones.
>>> That is basically what I said.  I don't have one that isn't part of a
>>> DecServer and i need images, or someone with a non DecServer to provide
>>> them.
>>> I guess you restated what I said.  if you have one, I'd appreciate
>>> copies.
>>> I didn't post the original link from the top of this thread, you might
>>> want to read it.  I'm just stating what someone did back in the 2001
>>> time frame and posted a page about the conversion and info on his
>>> experiences.
>>>> The note also mentioned that you might want/need to install a pull-up.
>>>> But it would still be an extremely simple process. You just need the
>>>> right bits...
>>> What I said.
>>>>     Johnny
>>>> On 2015-10-19 18:28, jwsmobile wrote:
>>>>> I would appreciate thoughts on the conversion of the processor to
>>>>> normal
>>>>> PDP11 eproms.
>>>>> The page pointed to earlier has a mention of that too, but the poster
>>>>> had access to another "real" KDJ and I am guessing copied that.
>>>>> I don't have access to any version of the system with appropriate
>>>>> eproms
>>>>> and would appreciate any pointers to the binaries needed.
>>>>> As to the condition most of the material is the result of moving it
>>>>> from
>>>>> where it was stored.  It will be totally disassembled and tested
>>>>> before
>>>>> being brought back up.  There is about 5 or 6 large deep freeze (for
>>>>> reference) sized piles of material being sent for e-waste from the
>>>>> place
>>>>> that is pretty much just junk material under the weather.
>>>>> Think of this as a Dusenberg rescued from a barn though.
>>>>> thanks for all the suggestions and observations.
>>>>> Next thing to go over is a Sun 4/260 "mini" tower.  Gads those were
>>>>> heavy.  Back is still aching from moving that.
>>>>> Jim
>>>>> On 10/19/2015 7:32 AM, Ethan Dicks wrote:
>>>>>> On Mon, Oct 19, 2015 at 3:42 AM, Pontus Pihlgren
>>>>>> <pontus at>
>>>>>> wrote:
>>>>>>> Interesting. I thought Tthe DECserver 550 was merely the big
>>>>>>> brother in
>>>>>>> the terminal server line. But it looks like it is essentially a
>>>>>>> PDP-11/53 with 1.5MW of ram, you need new boot roms though. Pretty
>>>>>>> nice.
>>>>>> Yep.  It's essentially an S-box KDJ11 with different ROMs.  I happen
>>>>>> to have a CPU board from one, but not the box itself.
>>>>>> One of these days, I plan to burn "real" PDP-11 ROMs and bring
>>>>>> 2.11BSD
>>>>>> up on mine.  That and my Pro380 are my only KDJ11 machines.
>>>>>> -ethan

Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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