My head is spinning with the innovation taking place here the last 10 years.
On Friday, July 24, 2020, 03:59:21 PM EDT, Stephen Adolph
<twospru...@gmail.com> wrote:
yah I think so. It is only slightly larger than the 40 pin socket. should
drop it place.
I can share the mods I made to the M100 ROM. You might have a hard time to get
a working ROM for NEC.The reason why is that, on the M100 ROM, I have a patch
that creates a BIG HOLE. I found an optimization in how the video code worked,
and my patch makes something like 170 bytes free in the ROM.I use that hole to
embed code to work around the various changes to back out / change the calls
that use SIM and RIM.
(The M100 rom does not make use of the undocumented commands of the 8085.
So it is a good challenge for you Gary- Modify the NEC ROM to work with NSC800.
..Steve
On Fri, Jul 24, 2020 at 3:40 PM Gary Weber <g...@web8201.com> wrote:
Great news!
Question for you: I know the dual-CPU board doesn't physically fit
into the socket space in the NEC machines, but would your single
NSC800 adapter fit just fine?
Gary
On Thu, Jul 23, 2020 at 7:38 PM Stephen Adolph <twospru...@gmail.com> wrote:
>
> Update.
> I have refined my NSC800 aka Z80 conversion for M100 somewhat.
>
> I now have a very simple adapter board that converts the 80c85 socket to
> accept NSC800. Small and simple. Plug and play.
>
> The main rom needs to change to a patched version that I have. To do so, you
> need to use one of the various means to convert the strange M100 main rom
> socket to something more standard.
>
> Why?
>
> Well I am still pushing towards a nice Z80 solution for CP/M.
>
> Besides.. the solution is so clean it is really cool. Hard to resist! The
> M100 could have easily been designed with this processor to begin with.
>
> So why not ;)
>
> My thinking is to offer this as a simple kit or maybe even just release the
> board. The BOM is really small. Processor is easy to get off ebay.
>
> One thing that would be nice, is a new version of tsdos that avoids all the
> special 80c85 opcodes....compatible with 8080. Then it could run on z80 as
> well.
>
> Even a patched teeny would be fine I suppose.
>
>
>
>
> On Thursday, July 11, 2019, Stephen Adolph <twospru...@gmail.com> wrote:
>>
>> Motivated by 2 things
>> 1) discovery of the NSC800 Z80 processor that is 80C85 like
>> 2) continuing to work in the direcition of CP/M
>> 3) and recalling that there are 5MHz 80C85 parts out there..
>>
>> I started to work on a dual CPU card for M100 that enables a couple of
>> things;
>> - standard 2.5MHz 80C85 operation (default)
>> - switchable clock for 80C85, supporting 5MHz
>> - switchable CPU enabling NSC800 at 2.5 MHz.
>>
>> Board is done and heading to the fab. VHDL is mostly done.
>>
>> I don't expect this board will be wildly popular but maybe it has some
>> interest Double speed M100 seems interesting on it's own, let alone being
>> able to support Z80 CP/M applications.
>>
>>
>> Any interest?
>>
>> I have purchased material to make 5 of these.
>>
>> A few more comments.
>> - to install this board you need to remove the 80C85. that's some effort to
>> do
>> - to run at 5MHz you need to upgrade the 81C55 to a 5MHz version. That's
>> also some effort.
>> - NSC800 runs about 5$ on ebay.
>> - fast 80C85 can be had for under 5$.
>> - fast 81C55 can be had for under 5$.
>> - to run at 5MHz you might also find you need a faster main ROM, and faster
>> RAM. TBD on that; will advise after I do some testing.
>>
>>
>>
