6809 instead of the 6502

Moto Rola · Post by **Moto Rola** » Mon Jun 13, 2022 11:34 am

On 6/12/2022 at 2:51 PM, Johan Kårlin said:

while 6502 might be more nostalgic the experience of programming it is rather tedious. Everything tends to be about handling low and high bytes .. But the 65816 were abandoned

You're totally right; so even the 65816 has been dropped? Not too good.

Moto Rola · Post by **Moto Rola** » Mon Jun 13, 2022 11:46 am

On 6/12/2022 at 6:26 PM, svenvandevelde said:

Well to be honest I am kind of glad that the 65C02 was selected, although it would have been nice if the 65CE02 would have been possible. The additional z register would really make a difference.

…let alone all 6809's additional registers and its much „stronger” ML… but well, if that „Commodore feeling” is really worthy that much…

rje · Post by **rje** » Mon Jun 13, 2022 1:49 pm

On 6/13/2022 at 6:34 AM, Moto Rola said:

You're totally right; so even the 65816 has been dropped? Not too good.

"Dropped" as in, an early decision that is made from initial brainstorms based on what you have at the time. The 65816 added hardware complexities that were odious. The project already has complexities. Adding one more is not necessarily a good thing, based on what your target is.

But it's always worth revisiting... for example, here:

Fabio · Post by **Fabio** » Mon Jun 13, 2022 2:06 pm

I wonder why none offers an unmultiplexed 65816: it shouldn't be so difficult and it would become a much more interesting alternative for hobbyists.

Scott Robison · Post by **Scott Robison** » Mon Jun 13, 2022 6:37 pm

On 6/13/2022 at 8:06 AM, Fabio said:

I wonder why none offers an unmultiplexed 65816: it shouldn't be so difficult and it would become a much more interesting alternative for hobbyists.

Simple supply and demand. There are not enough hobbyists to make it worth anyone's time or effort.

svenvandevelde · Post by **svenvandevelde** » Mon Jun 13, 2022 6:54 pm

On 6/13/2022 at 1:46 PM, Moto Rola said:

if that „Commodore feeling” is really worthy that much…

It is worth it, yes...

Scott Robison · Post by **Scott Robison** » Mon Jun 13, 2022 9:47 pm

On 6/13/2022 at 5:46 AM, Moto Rola said:

…let alone all 6809's additional registers and its much „stronger” ML… but well, if that „Commodore feeling” is really worthy that much…

That is a question that a person can only answer for him or her self. Spectrum Next is not for me but X16 is.

codewar65 · Post by **codewar65** » Mon Jun 13, 2022 11:35 pm

The 65816 was an abomination IMHO. If it had full dedicated address pins, I might say otherwise. lol

BruceMcF · Post by **BruceMcF** » Tue Jun 14, 2022 10:21 pm

On 6/13/2022 at 7:35 PM, codewar65 said:

The 65816 was an abomination IMHO. If it had full dedicated address pins, I might say otherwise. lol

Behind many design elements considered to be "abominations" by some often lurks that horrible phrase, "commercial considerations". AFAIU, Apple LIKED the smaller CPU footprint that resulted from multiplexing D0-D7 with A16-A23. Nintendo certainly did, and the design license fees flowing from the SNES was a much bigger cash cow than any 21st century hobbyist systems are ever going to be.

If used for a 64K address space for a 65xx family system, with RAM and I/O conditioned on PHI2 high, it seems to me that the high address space can simply be ignored.

Moto Rola · Post by **Moto Rola** » Wed Jun 15, 2022 12:09 pm

On 6/15/2022 at 12:21 AM, BruceMcF said:

If used for a 64K address space for a 65xx family system, with RAM and I/O conditioned on PHI2 high, it seems to me that the high address space can simply be ignored.

I found a few 65C816-based projects on YT and also googling around another few SBC designs. So probably that multiplexing can be managed somehow, I suppose?