shirsch
Veteran Member
Unfortunately this implementation is best suited for the CYCxxxx single-board computer which is pure unobtanium.
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Building a PDP-11 from scratch
- Thread starter maguro
- Start date
AK6DN
Veteran Member
That is only one choice of many FPGA boards. There are many other alternatives...
'best suited' is only applicable if your only criteria is absolutely smallest size.
shirsch
Veteran Member
I'm just going by what the author told me when I wrote to ask about CYC1000 availability. I have a couple of the alternate boards here and will try to dig back into the subject. Thanks!
sam2000
Member
Hello everybody, I am new to this forum, I read with interest that some of you is tackling with the idea of making his/her own pdp-11, and many actually succeeded, to some extent. I too would like to try this, my idea is to use a DCJ-11 cpu, not so sure about the FPJ11 21-21858 because they are hard to find, expensive and also I couldn't find its datasheet, pinout and schematics of suitable connection with the cpu. In my idea my system will use 32 bit eurocard board backplane, have 4MB of static RAM with zero wait state and be accessible also bytewise without corrupting the other pair of the word. For the I/O I was thinking at some serial port, parallel I/O, some hack for interfacing a sd card or an IDE hard disk, an RTC and an AUI Ethernet port. Cherry on the cake would be to use a PiDiP11 console case to mimic the /70.
I still have a long way to go, first by reading and studying everything that you already wrote on the subject, documentation, and experimentation. I hope to share with you all in the future some (good?) news. In the meanwhile thank you all for keeping alive this pdp idea.
Paolo
I still have a long way to go, first by reading and studying everything that you already wrote on the subject, documentation, and experimentation. I hope to share with you all in the future some (good?) news. In the meanwhile thank you all for keeping alive this pdp idea.
Paolo
marcopolo
Experienced Member
A VME backplane?
sam2000
Member
No, ECB backplane derived from the N8VEM project. "Derived" because that bus is not conceived for a PDP architecture and some signal name and usage shall be changed accordingly. I noticed that other users here went on that same road
sam2000
Member
Another benefit of the N8VEM ECBs is that for just 10 bucks you can find the bare unpopulated pcb online
daver2
10k Member
Before you go too mad (!) perhaps you need to think about what software you want to run, and how that will impact either your choice of hardware or whether you will have to write bespoke device drivers for your non-standard hardware.
Dave
Dave
sam2000
Member
I aim to run BSD 2.11, and indeed you are right, hardware-wise the I/O I need to implement will have to be as similar as possible to original DEC devices. I know other members (and non members) managed to adapt modern devices to mimic the original hardware, for instance the 6402 uart can be adapted to become a serial interface, other managed to create an hard disk interface, and the list goes on. As for writing my own device drivers, hmmm that will have to be seen accordingly to what will come up, but I will try to keep that as low as possible
daver2
10k Member
I thought I would just plant that seed in your mind...
What are your intentions for this board?
Is it for the interest of 'just doing it' or is there some other reason?
Dave
What are your intentions for this board?
Is it for the interest of 'just doing it' or is there some other reason?
Dave
sam2000
Member
Fair question, "just for the sake of it" would be the most honest answer. Of course I wish to learn something new, hone my skills and have loads of fun... but ultimately having a mockup of a PDP11/70 sitting on the shelf would be nothing if you can't power it up and make it work
daver2
10k Member
That's a fair enough answer... And probably the same answer most of us would give if truth be told...
It will keep you off the streets at least
!
Dave
It will keep you off the streets at least
!Dave
sam2000
Member
I'm still in the brainstorming phase, as soon I have read and studied enough I'll open a new thread with some more specific data. I'm open to all suggestionsThat's a fair enough answer... And probably the same answer most of us would give if truth be told...
It will keep you off the streets at least
Dave
pbirkel@gmail.com
Veteran Member
Well, those would very likely be only A-C connectors (64-pin) which may not be sufficient for your purposes (Qbus is 72-pin, right?).
A-B-C DIN connectors (96-pin) are much more expensive and harder to obtain, as well as backplanes, because you've moved into VME territory.
sam2000
Member
Indeed I'll have to check that, but I kind of remember reading the N8VEM ECB backplane was expanded years ago in order to support 16 bit systems, with 24 bits of address space, so this would fit perfectly.
pbirkel@gmail.com
Veteran Member
The 8-slot backplane is indeed ABC (schematic attached). So is the 12-slot backplane (schematic attached). But once you price in the pairs of 96-pin connectors you may find it cheaper to acquire an existing "half-VME" backplane. Or a full VME backplane; think of it as QQ/CD (or QQ/QQ). And you'll have a more favorable board size to work with. At which point simply adopting a 4-tab DEC Qbus backplane begins to look ... favorable! It's a slippery slope, yes ...
marcopolo
Experienced Member
@sam2000
I have the same project as you, building a PDP-11 with a DCJ-11 CPU, I've bought a few.
However, I'm thinking of using 4 DIN41612 48-pin connectors to make it look like the original Qbus.
For this project, I want to use contemporary components from the DCJ-11 (1983-1990), no SMD parts, no big CPLD
I think you know this site (ECB bus for PDP-11) :
www.5volts.ch
Perhaps you could open a dedicated topic so as not to pollute @maguro 's subject?
I have the same project as you, building a PDP-11 with a DCJ-11 CPU, I've bought a few.
However, I'm thinking of using 4 DIN41612 48-pin connectors to make it look like the original Qbus.
For this project, I want to use contemporary components from the DCJ-11 (1983-1990), no SMD parts, no big CPLD
I think you know this site (ECB bus for PDP-11) :
System Bus · My PDP-11 Projects
www.5volts.ch
Perhaps you could open a dedicated topic so as not to pollute @maguro 's subject?
Last edited:
sam2000
Member
You are so right, I'll make some order in my ideas and open a new thread@sam2000
I have the same project as you, building a PDP-11 with a DCJ-11 CPU, I've bought a few.
However, I'm thinking of using 4 DIN41612 48-pin connectors to make it look like the original Qbus.
For this project, I want to use contemporary components from the DCJ-11 (1983-1990), no SMD parts, no big CPLD
I think you know this site (ECB bus for PDP-11) :
System Bus · My PDP-11 Projects
Perhaps you could open a dedicated topic so as not to pollute @maguro 's subject?
thephysicist
Experienced Member
you mentioned on the hackaday site a gitlab repo - could you please share a link to that repo too?
thanks
Michael