6 Apr
2002
6 Apr
'02
5:26 a.m.
In a project I'm thinking about starting this summer, I want to try and
re-create a PDP-11 (or maybe a -8 or something) using either SSI logic
and/or PAL/GALs. I would like to do the entire thing in SSI, but I fear
that I'd quickly eat up a lot of money on the project, so where necessary
I'd replace sections with PALs. Anyone have any good ideas?
About what I'm doing: Trying to replicate an 'old-computer feel' for a
mock airport that a friend of mine is thinking about making. I'll have a
good amount of time to work on designing it before I start laying down
copper on a circuit board. I'd like to make something that 1) looks
authentically old and 2) has a design I can (semi-legally, not for resale)
copy so I don't have to do all the re-design work myself.
I've considered just using a plain-old Apple //e that I have, but that
wouldn't be 'old enough' looking I was thinking. It'll need to have a
good amount of I/O, and be easy enough that I can actually build it and
understand how to program it without much effort. By that way, I don't
care about using 'standard OS's' or 'standard hardware' too much, I
just
want to put together a system with a CPU, serial port, and some sort of
floppy drive interface (I prefer 5-1/4 disks at some PC readable format)
it can boot off of - or perhaps an IDE interface as that would be easy to
program a 'driver' for (or so I'm told).
Does anyone have any suggestions for what I should try to build? Eg. what
model PDP-11 cpu card, what prints I should get to try and assemble a
basic working system, etc. Should I try something else? I would like to
go a bit overboard, the look is a part of the thing, but I don't want to
screw with finding things like QBUS drivers, and don't think I'll want to
bother with a 'traditional mini-computer bus' if I don't need to.
This is what I have so far:
1) CPU card
2) Memory - SRAM
3) Front-panel switches
4) Console serial port
5) A few digital I/O ports
6) Floppy interface (anyone suggest an easy to interface controller?)
7) IDE controller
-- Pat
6 Apr
6 Apr
6:15 a.m.
pat(a)cart-server.purdueriots.com wrote:
[Building some mock PDP computer]
If you want something which is very easily programmable, then go for a
PDP-8. I had no problem learning how to code a few useful programs in
PDP-8 assembler using some documents from the web. You shoudl have a
look at what this guy did. It is very similar to what you are trying to
do if I read you correctly.
http://www.spies.com/~dgc/
Thomas
--
Thomas S. Strathmann http://pdp7.org
If God had intended Man to Smoke, He would have set him on Fire.
6:39 a.m.
pat(a)cart-server.purdueriots.com wrote:
In a project I'm thinking about starting this summer, I want to try and
re-create a PDP-11 (or maybe a -8 or something) using either SSI logic
and/or PAL/GALs. I would like to do the entire thing in SSI, but I fear
that I'd quickly eat up a lot of money on the project, so where necessary
I'd replace sections with PALs. Anyone have any good ideas?
(snip)
1) CPU card
2) Memory - SRAM
3) Front-panel switches
4) Console serial port
5) A few digital I/O ports
6) Floppy interface (anyone suggest an easy to interface controller?)
7) IDE controller
Barring #7 can I sell you the nice 12/24 bit FPGA cpu I homebrewing. :)
The PDP-11 is way too complex for SSI logic. A reduced PDP-8 style cpu
would be possible with SSI logic. While not true SSI logic modern
EEPROMS would be very useful for control logic. Byte magazine had a few
TTL designed cpu's. Stack based languages like Forth are easy to do in
TTL. I would have done my FPGA computer in TTL but nowadays you can't
find the 74LS chips I needed anymore like 74ls382 4-bit alu. One other
option is 2901 bit slice parts. B.G.Micro seems to have a few in stock.
If I were to redesign I would use 2901 bit slice parts and EEPROMS for
control now that I know where to find 2901's.
A floppy disk controller interface is fairly simple but you need a fast
CPU for the disk if some sort of DMA is not used. That is why my FPGA
computer is not quite finished , I am squeezing in DMA for HD floppies.
Also the front panel logic needs a bit of work too.
If you really want to be authentic don't forget to add Refresh logic on
the CPU for DRAM.
--
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html
8:59 a.m.
On Sat, 6 Apr 2002, Ben Franchuk wrote:
pat(a)cart-server.purdueriots.com wrote:
I'm trying to avoid any more integration than a PAL or EPROM would
provide. Thannks for the offer anyhow. :)
In a project I'm thinking about starting this summer, I want to try and
re-create a PDP-11 (or maybe a -8 or something) using either SSI logic
and/or PAL/GALs. I would like to do the entire thing in SSI, but I fear
that I'd quickly eat up a lot of money on the project, so where necessary
I'd replace sections with PALs. Anyone have any good ideas?
(snip)
1) CPU card
2) Memory - SRAM
3) Front-panel switches
4) Console serial port
5) A few digital I/O ports
6) Floppy interface (anyone suggest an easy to interface controller?)
7) IDE controller
Barring #7 can I sell you the nice 12/24 bit FPGA cpu I homebrewing. :) The PDP-11 is way too complex for SSI logic. A reduced
PDP-8 style cpu
would be possible with SSI logic. While not true SSI logic modern
EEPROMS would be very useful for control logic. Byte magazine had a few
Yeah that might be a good idea.
TTL designed cpu's. Stack based languages like
Forth are easy to do in
TTL. I would have done my FPGA computer in TTL but nowadays you can't
find the 74LS chips I needed anymore like 74ls382 4-bit alu. One other
option is 2901 bit slice parts. B.G.Micro seems to have a few in stock.
If I were to redesign I would use 2901 bit slice parts and EEPROMS for
control now that I know where to find 2901's.
I know it's not a conventional way to do it, but if I design my own CPU I
might just use a few EPROMS - at least for multiplicaion and divison, and
perhaps for addition and subraction. If I only do an 8-bit proc (very
likely), that's doable in a 256k*8 and a 128k*8 EPROM, running me only
less than $12 for 120ns parts and only 64pins in two chips to implement
all of the difficult ALU functions. AND, OR, etc should be easy and
cheaper to do with 74* TTL or CMOS IC's. Either battery-backed SRAM or
(E)EPROM for the state controller should be cheap, easy, and effective.
Mind you, I haven't bothered looking around for prices yet, so things may
actually be cheaper.
A floppy disk controller interface is fairly simple
but you need a fast
CPU for the disk if some sort of DMA is not used. That is why my FPGA
computer is not quite finished , I am squeezing in DMA for HD floppies.
Also the front panel logic needs a bit of work too.
I might think about using an 80xx series DMA controller and a
semi-standard WDC floppy controller like those used in PeeCees so I can
get easy acces to docs for them. However, I might not bother adding in
the fdd stuff or hdd stuff - as long as I can get the code to fit onto an
SRAM or something I should be OK. I just have to figure out what I want
to do before I go any further.
I just
If you really want to be authentic don't forget to
add Refresh logic on
the CPU for DRAM.
That's OK, I'll deal with the non-authentic feel of battery-backed SRAMs.
Anyhow, the SRAM will act more like some core memory. :)
-- Pat
10:15 a.m.
pat(a)cart-server.purdueriots.com wrote:
I know it's not a conventional way to do it, but if I design my own CPU I
might just use a few EPROMS - at least for multiplicaion and divison, and
perhaps for addition and subraction. If I only do an 8-bit proc (very
likely), that's doable in a 256k*8 and a 128k*8 EPROM, running me only
less than $12 for 120ns parts and only 64pins in two chips to implement
all of the difficult ALU functions. AND, OR, etc should be easy and
cheaper to do with 74* TTL or CMOS IC's. Either battery-backed SRAM or
(E)EPROM for the state controller should be cheap, easy, and effective.
While 8 bits are OK for a 8 bit data path, you still need more than 8
bits for a practical program counter address space. That is where 12
bits are practical has room for useful instructions. Here is a nice
small 8 bit FPGA design that could be easily adapted to TTL.
http://www.tu-harburg.de/~setb0209/cpu/
A 8 bit FPGA computer http://germanium.ee.wustl.edu/ToyCPU/toy_cpu.html
Simplex real a 8 bit TTL computer with about 120 chips.
http://members.iinet.net.au/~daveb/simplex/simplex.html
I might think about using an 80xx series DMA
controller and a
semi-standard WDC floppy controller like those used in PeeCees so I can
get easy acces to docs for them. However, I might not bother adding in
the fdd stuff or hdd stuff - as long as I can get the code to fit onto an
SRAM or something I should be OK. I just have to figure out what I want
to do before I go any further.
A IDE disk interface may be a simpler design, and faster than a floppy.
That's OK, I'll deal with the non-authentic
feel of battery-backed SRAMs.
Anyhow, the SRAM will act more like some core memory. :)
I plan later to use a EEPROM bootstrap that I can load from the front
panel, once I decide on a I/O device -- floppy disk or IDE drive. I got
a nice hardware bootstrap that can load from serial console/paper tape
(If I had a reader/punch that is), front panel or a 4 bit wide prom.
--
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html
2:19 p.m.
The SBC6120 (PDP-8 board) uses an IDE drive in LBA
mode, simply stating, "on address X read or write
these 256 16(12) bit words". Because this obviously
requires a great deal of intelligence on the drive's
part, (certainly more than the computer itself has) I
suppose that philosophically speaking, this is
"cheating"....
--- Hans B Pufal <hansp(a)aconit.org> wrote:
Ben Franchuk wrote:
__________________________________________________
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A IDE disk interface may be a simpler design, and
faster than a floppy.
And can be easily adapted to use CompactFlash for
smaller/lower power
systems.
-- hbp
4:43 p.m.
Loboyko Steve wrote:
The SBC6120 (PDP-8 board) uses an IDE drive in LBA
mode, simply stating, "on address X read or write
these 256 16(12) bit words". Because this obviously
requires a great deal of intelligence on the drive's
part, (certainly more than the computer itself has) I
suppose that philosophically speaking, this is
"cheating"....
Bigger YES! Cheating no!
Other than stupid floppies and the old HD's on the PC where you just get
raw data from the drive, almost all the interfaces for disks have been -
set track / sector / head and buffer address then a read/write a block
to memory command. With a machine as small as pdp-8 you had very dense
I/O routines compared to today's machines that need 64kb?? of bios for
basic I/O. The last page (128 bytes??) was often all the room you had
for a disk driver that often swapped the entire 4k of memory to and from
disk. As for the cpu on the HD it is more powerful than a pdp-8 but then
HD's are a hell of a lot faster than in the 1960's that were often only
FM formatted hard sectored machines.
--
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html
8139
days inactive
8139
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7 comments
5 participants
participants (5)
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bfranchuk＠jetnet.ab.ca -
hansp＠aconit.org -
pat＠cart-server.purdueriots.com -
sloboyko＠yahoo.com -
thomas＠tstrathmann.de