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Mr SQL
Registered: Feb 2023
Posts: 159 |
C64 Compatibility with C128 in depth
Very educational video on 8-bit show and tell:
http://www.youtube.com/watch?v=Ial2VSAu7tw
Robin illustrates using the built-in dissembler/Editor Assembler to correct hotspots where the C128 is incompatible with the C64.
The C128 is still closely compatible for having enhancements to the same hardware. I remember when the CoCo III came out the GIME did not fully emulate the 6847 VDG creating more incompatibilities, particularly with the semigraphics modes.
Interesting commentary at the end of the video regarding the C64 mode being better for game development. |
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chatGPZ
Registered: Dec 2001
Posts: 11523 |
Quote:I was reading the Compute manual and like the fact that the new 6502 variant has a Direct Page that is moveable like the 6809 instead of having to stay on the zero page, that is a great programming feature for enhanced C64 programming.
What are you talking about? That's a MMU feature, it has nothing to do with the CPU. It can't be used in C64 mode either. |
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oziphantom
Registered: Oct 2014
Posts: 502 |
Quoting Mr SQLPerhaps this was done to distinguish it on the C128.
On the C64 shift-lock is indistinguishable from left shift, it uses the same keyboard matrix.
No.
The Shift-Lock key on a C128 is identical in every way to the C64 Shift-Lock Key. Otherwise it wouldn't work on the C64 Kernal or with games. As it is still wired to the Shift key and is in the same position on the keyboard. You can also do the fancy trick to detect Shift-Lock vs Shift on a 128 just fine. It is 100% identical.
The Caps-Lock key is a 128 only key and is not visible to the C64 Kernal, as it performs a Caps Lock operation not a Shift Lock operation it is has very different functionality. |
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Mr SQL
Registered: Feb 2023
Posts: 159 |
Quoting chatGPZQuote:I was reading the Compute manual and like the fact that the new 6502 variant has a Direct Page that is moveable like the 6809 instead of having to stay on the zero page, that is a great programming feature for enhanced C64 programming.
What are you talking about? That's a MMU feature, it has nothing to do with the CPU. It can't be used in C64 mode either.
Thanks I thought it was a modification directly to the new 6502 variant. It seems to have the same function for the CPU as the one built into the 6809 where you can change the direct page to any of the 256 pages to use zero page addressing there.
On the CoCo III the MMU was limited to manipulating 8K blocks, I'll have to finish reading the guide but it sounds like the MMU is more versatile on the C128. |
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Mr SQL
Registered: Feb 2023
Posts: 159 |
Quote: Quoting Mr SQLPerhaps this was done to distinguish it on the C128.
On the C64 shift-lock is indistinguishable from left shift, it uses the same keyboard matrix.
No.
The Shift-Lock key on a C128 is identical in every way to the C64 Shift-Lock Key. Otherwise it wouldn't work on the C64 Kernal or with games. As it is still wired to the Shift key and is in the same position on the keyboard. You can also do the fancy trick to detect Shift-Lock vs Shift on a 128 just fine. It is 100% identical.
The Caps-Lock key is a 128 only key and is not visible to the C64 Kernal, as it performs a Caps Lock operation not a Shift Lock operation it is has very different functionality.
Thanks that was confusing, caps-lock and shift-lock are often synonymous. Interesting it has another function.
I'm pretty sure shift-lock uses the same keyboard matrix circuitry as the left shift and just holds it down, they should be indistinguishable if that is the case. |
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chatGPZ
Registered: Dec 2001
Posts: 11523 |
Its the same in the keyboard matrix - but they still can be distinguished - see here: https://sourceforge.net/p/vice-emu/code/HEAD/tree/testprogs/CIA.. |
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