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Author Topic: Why C= never made a 65816 based machine?  (Read 7768 times)

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Offline psxphill

Re: Why C= never made a 65816 based machine?
« on: August 06, 2012, 01:06:40 PM »
Quote from: WolfToTheMoon;702467
Perhaps it would be dangerously close to lower spec Amigas, but I think it made sense to try and build on the foundations of 20ish millions of C64 sold and the huge software library that existed.

A 65816 wouldn't have been compatible with alot of the existing software & commodore were happy to just keep milking the c64.
 

Offline psxphill

Re: Why C= never made a 65816 based machine?
« Reply #1 on: August 06, 2012, 03:43:40 PM »
Quote from: Hattig;702482
Just this morning I was thinking that C= should have reduced the C64 to a single chip (including the VICII,SID,6502,Serial,etc) by the late 80s so that they could sell it for cheap in developing countries for a profit. It could also have been clocked higher because said chip would have been fabricated on a far more modern process than the original C64.

I think the 8 bit line was actually quite well managed. They did reduce chip count and cost & because they could run the chips on their own lines they were very cheap to make. Anything more would have involved a massive investment, which wouldn't have been a good gamble.
 

Offline psxphill

Re: Why C= never made a 65816 based machine?
« Reply #2 on: August 06, 2012, 04:38:11 PM »
Quote from: WolfToTheMoon;702504
It was still 8 bit and pretty limited. .. I was thinking more of a next generation entry machine...a 16 bit CPU, expandable RAM, 3.5" floppy, GUI based OS...

Sounds like an a500
 

Offline psxphill

Re: Why C= never made a 65816 based machine?
« Reply #3 on: August 06, 2012, 06:58:15 PM »
Quote from: WolfToTheMoon;702512
yes it does, but it would be cheaper and have backwards compatibility with C64 software. Plus, a 20 MHz 65816 is faster than a 7 MHz 68000 so it could a very interesting package. Timeframe around the original C65, 90-91', A500 would be replaced with A1200 in a year, A600 would not be needed.

 
It wouldn't have had meaningful backwards compatibility, just like the C65.
In 1989 they should have had an 020 machine with chunky graphics.
 

I'm not sure that the 20mhz 65816 used by CMD was available that early either.
« Last Edit: August 06, 2012, 07:15:13 PM by psxphill »
 

Offline psxphill

Re: Why C= never made a 65816 based machine?
« Reply #4 on: August 06, 2012, 08:31:02 PM »
Quote from: WolfToTheMoon;702531
Around 90', max from WDC was 12MHz... Doesn't really matter, even a 7 MHz 65816 will be more than fast enough.
Compatibility can be improved thru emulation.

You wouldn't be able to do it, if you emulated the 6502 your timing would be all wrong & you don't have enough processing power to emulate enough in software to relax the timing issues.
 
By 1990 the amiga was underpowered, spending money on developing another underpowered computer doesn't make sense.
« Last Edit: August 06, 2012, 08:34:25 PM by psxphill »
 

Offline psxphill

Re: Why C= never made a 65816 based machine?
« Reply #5 on: August 06, 2012, 09:18:59 PM »
Quote from: WolfToTheMoon;702537
There's no need to emulate 6502, there's a compatibility mode in 65816.

It's not compatible enough. Both for timing and the instruction set.
 
To make it faster than an a500 would require faster memory than an a500. It wouldn't have been cost effective enough.
 
To achieve the price you wanted would require you to aim around the same speed as the c65/snes/iigs.
 

Offline psxphill

Re: Why C= never made a 65816 based machine?
« Reply #6 on: August 15, 2023, 04:53:28 PM »
I discovered with the W65C816SXB board that it was not working correctly in emulation mode

Interesting thread here too.

http://forum.6502.org/viewtopic.php?f=1&t=5803

It looks intentional


or the base is specified by sixteen bits and assumes the data bank as its bank, then, if an index plus the low-order sixteen bits of its base exceeds $FFFF, it will temporarily (just for the current instruction) increment the bank. The 65816 assumes that the array being accessed extends into the next bank.
« Last Edit: August 15, 2023, 04:57:27 PM by psxphill »
 

Offline psxphill

Re: Why C= never made a 65816 based machine?
« Reply #7 on: August 16, 2023, 10:45:37 PM »
The 65816 was (briefly) considered for the C128 design

Bil Herd tells a different story. That he received a call from Bill Mensch trying to get him to use the 65816, which he immediately refused.

It wouldn't be commodore 64 compatible & it would be a chip they had to buy from an external company.
« Last Edit: August 16, 2023, 10:46:35 PM by psxphill »