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Re: [N8VEM-S100:1818] S-100 68K CPU board V3

I basically agree with you when the processors are 16 bit or less - I think the S100 gets a little less interesting for 32 bit processors and becomes more of a slow I/O bus for legacy stuff.  I don't know what is out there for 32 bit and beyond as most of it becomes SBC or proprietary.  Maybe Multibus II might be a solution or VME (though VME seems to be more for 68XXX flavor processors than general support).

It is fun to build things - I just get more out of them when they do more than blink leds :)  I actually depended on a system like this for my PhD thesis so it brings back a lot of good memories.

On Wednesday, August 14, 2013 1:03:00 PM UTC-5, monahanz wrote:

Spoken like a true software guy Dave!


I think there are varying interests in the group.  Personally I just like “messing with chips”, for any one of these board there are numerous permutations and combinations as to how they could be built.  If you just want to work with one CPU/software/application, then a SBC is probably the way to go.  The one thing the S-100 bus has going for is that it has the capability of housing (in theory) up to 16 CPU/DMA controllers. So if you want to have a computer that has multiple CPU’s or develop hardware/software for one CPU using another there is something to be said for the S-100 bus approach. 


Could this be done in hardware in other ways – absolutely.  The fact that there is an agreed upon standard and literally thousands of S-100 boards still out there makes it easier to get going, certainly for 8 bit CPU’s, a few 16 bit CPU’s and now hopefully with 32 bit CPU’s.


My current system has a Z80, a 6502, an 8086, an 80386 and 68010 CPU all working together in one box.  All do (or will) share the same hardware i.e. RAM, FDC HD controller, video, printer etc.. BTW, we need software guys like you to make this better!

Is there a commercial need for this, absolutely not.  Is it fun, yes (most of the time).   The future other CPU’s like the new 32 bit Propeller (when it comes out), ARM’s,  XVGA board,  SCSI etc. 


That’s just me, others may differ!







John Monahan Ph.D

e-mail: mon...@vitasoft.org

Text:    mon...@txt.att.net



From: n8ve...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of yoda
Sent: Wednesday, August 14, 2013 10:09 AM
To: n8ve...@googlegroups.com
Subject: Re: [N8VEM-S100:1818] S-100 68K CPU board V3


Hi Andrew!


I guess the real question to me is what are we doing?  Are we building / designing hardware because we can or is there a higher purpose.  I am basically a software guy that likes to dabble in hardware and I don't see a lot of software being created for all these boards (maybe the software folks are being really quiet).  Like I tell my hardware compatriots at work - you are just building an expensive pile of sand (silicon) without the software to be able to use it.


I think SBC is probably the better way to go as the S100 bus is becoming a more expensive I/O bus for these more powerful processors and in the end limits their speed and adds more complexity.  Maybe we should explore a better bus structure for these more powerful processors?


Just my thoughts - would be nice to hear what others think.  No use building a jet engine to place in a Model T Ford ?



On Wednesday, August 14, 2013 10:27:01 AM UTC-5, lynchaj wrote:


On the S-100 80386 CPU board there is a special connector “over the top” for memory boards with full 32 bit addressing and 32 bit data width.  The S-100 bus serves for accessing base memory and IO mostly since it is limited to 24 bit addressing and 16 bit data width.  The S-100 80386 CPU board can work with just bus memory but is limited to 16MB of 16 bit wide memory and is going to be slower than with the special memory board.


Assuming we move forward with a more advanced 68K series processor (68020, 68030, 68040, etc) on the S-100 bus I recommend a similar approach if not the same “over the top” memory boards to make them more economical and provide a useful amount of RAM to more powerful CPUs.  I was considering using the PAK68 approach for a 68020 or 68030 CPU socket mezzanine board for the S-100 68K board but in retrospect it would probably be better to design a new board instead.


Thanks and have a nice day!

Andrew Lynch


From: n8ve...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of yoda
Sent: Tuesday, August 13, 2013 3:09 PM
To: n8ve...@googlegroups.com
Cc: cct...@classiccmp.org
Subject: Re: [N8VEM-S100:1814] S-100 68K CPU board V3


Not sure it makes sense on an S-100 board as the address space is limited to 16 MB.  It will probably be an SBC with a couple hundred MB of memory - when we start getting in the GB range it is not quite as practical and the old chips are limited to 4GB anyway without a lot of additional memory decode tricks.  I can probably get old version of NetBSD flavor running on even a 68K with some tricks - at least I will be able to gauge the complexity.


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