2 Jan
2013
2 Jan
'13
9:18 p.m.
With lots of help from members of this forum and other friends I made
a high-speed paper tape reader emulator from a wire-wrapped interface
board and an Emcraft SmartFusion FPGA evaluation board. The interface
board plugs onto the Posibus interface slots in a PDP-8/L.
I loaded Focal from a BIN paper tape image into a PDP-8/L in about 2
seconds. That equates to about 3000 characters per second.
I put some details about the project here:
https://sites.google.com/a/ricomputermuseum.org/home/Home/equipment/pdp-8-l…
I will make an expanded version of the interface board and change to
the Emcraft SOM FPGA board. That will give me enough I/O pins to
emulate just about any peripheral that you can connect to the Posibus.
It would be possible to make an interface board for the Negibus so
that the peripheral emulator could be used on earlier PDP-8 systems.
--
Michael Thompson
3 Jan
3 Jan
3:06 p.m.
On Wed, Jan 2, 2013 at 9:18 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
With lots of help from members of this forum and other
friends I made
a high-speed paper tape reader emulator from a wire-wrapped interface
board and an Emcraft SmartFusion FPGA evaluation board.
Nice.
The interface board plugs onto the Posibus interface
slots in a PDP-8/L.
The PDP-8/L (and PDP-8/i) has slots for a PC8L (or PC8I). While I
applaud anyone who gets a Posibus peripheral working, I wouldn't have
thought that you could have just tapped into the slots for the PC8L
directly at TTL levels (no open collector bus fiddling).
I will make an expanded version of the interface board
and change to
the Emcraft SOM FPGA board. That will give me enough I/O pins to
emulate just about any peripheral that you can connect to the Posibus.
That's far more useful than just a papertape emulator.
Vince can probably tell you that I've wanted an "RX8L" for some time.
I have a PDP-8/L with 12K (via BM08L expansion cabinet) on which I've
wanted to run OS/8 for 25 years but have never had mass storage for.
Adding an RX01 to a PDP-8/L seemed to be the "simplest" solution at
one point.
It would be possible to make an interface board for
the Negibus so
that the peripheral emulator could be used on earlier PDP-8 systems.
That would also be useful - I have a PDP-8/i that I'd love to get
above 4K that I'd also love to run OS/8 on but I figured that the -8/L
would happen first since it already had enough core.
-ethan
4:13 p.m.
On 1/3/13 1:08 PM, Adrian Stoness wrote:
is there such a thing?
M8350 KA8E External positive I/O bus interface
On Thu, Jan 3, 2013 at 2:49 PM, Al Kossow <aek at
bitsavers.org> wrote:
On 1/3/13 12:40 PM, Adrian Stoness wrote:
will this work with an 8a?
you would need an omnibus to posibus interface board
4:19 p.m.
txs
On Thu, Jan 3, 2013 at 3:13 PM, Al Kossow <aek at bitsavers.org> wrote:
On 1/3/13 1:08 PM, Adrian Stoness wrote:
is there such a thing?
M8350 KA8E External positive I/O bus interface
On Thu, Jan 3, 2013 at 2:49 PM, Al Kossow <aek at bitsavers.org> wrote:
On 1/3/13 12:40 PM, Adrian Stoness wrote:
will this work with an 8a?
you would need an omnibus to posibus interface board
4:38 p.m.
From: Michael Thompson: Wednesday, January 02, 2013 6:18 PM
With lots of help from members of this forum and other
friends I made
a high-speed paper tape reader emulator from a wire-wrapped interface
board and an Emcraft SmartFusion FPGA evaluation board. The interface
board plugs onto the Posibus interface slots in a PDP-8/L.
I loaded Focal from a BIN paper tape image into a PDP-8/L in about 2
seconds. That equates to about 3000 characters per second.
Nice! It is good to see someone actually get a PDP-8 FPGA peripheral of
this sort working. A number of folks have talked about it, but not got
anything actually running. ( know of at least one success with a PDP-11,
though.)
I will make an expanded version of the interface board
and change to
the Emcraft SOM FPGA board. That will give me enough I/O pins to
emulate just about any peripheral that you can connect to the Posibus.
That should make possible the RX08 emulation that Ethan is looking for.
That doesn't even need DMA/Data Break, just both directions of Posibus.
It would be possible to make an interface board for
the Negibus so
that the peripheral emulator could be used on earlier PDP-8 systems.
Seems like that should be straight-forward. There aren't a whole bunch
of working examples of those left, though :-(.
I like Posibus, since all the later machines (including Adrian's 8/A) have
Posibus as an available interface, and the conversion to/from Negibus
is just voltage level conversion. So if one does a Posibus peripheral,
it seems like it should be useful on 'most any PDP-8 (DECmate, not so
much). It's also dead simple, though it uses a fantastic amount of wire
and connectors, especially by today's standards.
Good work!
Vince
4167
days inactive
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aek＠bitsavers.org -
ethan.dicks＠gmail.com -
michael.99.thompson＠gmail.com -
tdk.knight＠gmail.com -
vrs＠msn.com -
wilson＠dbit.com