help a lot.
Post by Alan HightowerI think there maybe a better option. I've been noticing some of the older
PLCC based 5V PLDs from Lattice are available on Digikey. Lattice provides
a reference design for a FPM DRAM controller. Should be possible to do a
couple 72-pin DIMM through-hole sockets and an 84-pin PLCC through hole
socket proof of concept with minor modifications. Best you could do is
60ns but it would be 256MB total capacity. And I have some time next week
to work on it.
-Alan
Sent from my iPhone 4S
Hi Andrew
Think I better post some comments here. The 68040 is probably a long ways
off. The 68360 board that Andrew and I worked on is somewhat functional
but after working with it for a while, I have decided that is not the way
to go. It is just too complex a programming model and would be very under
utilized ultimately. It would also require some complex CPLDs as glue when
interfacing with the 68040.
My thoughts are to go with a straight 68040 design - the challenge as
Andrew has described is the memory and rom. 68040 does not have dynamic
bus sizing so memory has to be 32 bits. The densities of through hole
chips are just not there to support that. I am looking at ways to get
higher density memory support through FPGA proto boards that support sdram
on them. The Xess Xula series looks attractive for this but does not bring
out enough I/O pins to do this, though there have been discussions on the
Xess yahoo forum for a new version that would double the I/O pins by adding
another row of header pins on both sides. There are other FPGA boards on
ebay that also bring out a lot of I/O pins that might work as well.
I don't plan to start on this until I can clear out some projects that
need to get done first that will be stepping stones for the 68040. The
1) complete the port and bring up of CP/M 68K on the S100-68K-V3 board. I
hope to have time to do this during the Xmas break. My real job has gotten
in the way of my hobby time. This will validate the tool chain I am using
(gcc cross compiler generating ELF output). I have parts of the monitor
already working (getc, putc, printf) so I am making progress.
2) bring up the propeller console I/O with 1 above - this should be
relatively trivial - just have to complete board and check it out in system
3) Build a Interrupt / timer board - don't know if Andrew is going to send
out for more boards on that one so I am going to build one in the meantime.
I am going to use the Xula FPGA for this as there are a couple other
things I want to do as well with this board. I am in general a software
person so this will be my first foray into HDL work though it doesn't look
too bad as long as I don't get tricked into sequential flow from my
software background. I plan to expand usage of the Xula to be a text and
graphics VGA adapter as well.
4) With the 3 things above in place - I will start looking at porting
uCLinux to the S100 system. I may also look and a port of EmuTOS and MINT
as well.
5) Will design a small board with 68040, rom, and ram with 3 above. Get
a working monitor program to function with the board. I will probably use
some memory that is 48BGA and hope to make a small through hole adapter for
the memory - might get that assembled elsewhere. Once I get that working
figure out how to put some SDram on the board.
As you can see there is a lot of work that needs to proceed building a
68040 system and having a chance of it working. I will probably do parts
of 5 after step 1 is complete above as there will be time waiting for
boards to be made, etc to accomplish the other steps.
Post by Andrew LynchHi
About last year or so Yoda and I were building a 68040/68360 based SBC.
There are schematics and PCB layout on the wiki. I haven't heard any
updates on the design recently but I recall it was working (the P1) at
least with the 68360. Might want to check with Yoda to see where it was
at. I recall the serial port was working and he was going to interface a
"PropTerm" like function. The initial (P1) prototype used small Flash and
SRAM but the longer term plan was to go with DRAM for a decent sized memory.
The P1 needs an update. I think Yoda was considering doing away with the
68360 but then so much logic would be needed to replace it the board would
either be huge or require fairly dense PLDs.
Thanks and have a nice day!
Andrew Lynch
*Sent:* Tuesday, December 3, 2013 11:43 PM
*Subject:* RE: [N8VEM: 16599] MC68040 board supplies
Hi Jim!
Im really impressed! I want to build a 680x0 computer myself. I found
a bunch of MC68012RC10s on ebay recently that can address 2GBs of ram if I
remember correctly. I was amazed. I didnt think any of the 680x0 mpus
could do that. I have been wondering about the higher 680x0 processors,
but I have not researched them yet since it seems a 680x0 based computer is
a bit in the future. I would like to see 680x0 single board computer
schematics of some kind. It would be fun to create the Ultimate Super
Disk Extended Color Basic in say 1Mbits of eprom! Just think all the
commands you could put into that! What could we do with a 68060 based
Ultimate Color Computer? How about networking 64 of them together and
creating a parallel processing super computer with them! Hummm
Im
drooling! Slurp! Id like to see any plans you may have rolling around in
your neck-of-the-woods. Should I scarf up a few 680x0s. If so, which
ones? Thanks a bunch. Take care my friend.
Kip
Behalf Of *James Igou
*Sent:* Tuesday, December 03, 2013 5:58 PM
*Subject:* [N8VEM: 16599] MC68040 board supplies
Hi, I know you guys are already discussing this and it definitely
interests me as 68030 perform significantly worse and 68060 are getting
more pricey.
I have purchase one 33MHz 68040 and will stockpile a few more.
I have a suspicion that this processor will follow the '060 in its
pricing and availability.
So hopefully, by the time you have a board worked out, I'll have a good
supply of affordable chips.
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