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Post by mirkosoft on Nov 24, 2019 0:25:01 GMT
Hi!
I have very simple question but hard to find answer. Is possible to turn off Kernal and maybe even Basic in Commodore 128 and then for bank 15 leave visible RAM? Anything similar to C64 where is possible to use RAM under Kernal and Basic. You're asking what a dumb Q I have when we have bankswitching? Yes, we have. But what I need: Have visible RAM content even when is bank 15 selected and all other selected to have visible only RAM content instead ROM content.
Here's also Q2: how is location $0000 and $0001 different to C64? I know their function, but need compare from any C64 user.
Thank you for your help. Miro
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Post by bjonte on Nov 24, 2019 6:45:07 GMT
But what I need: Have visible RAM content even when is bank 15 selected and all other selected to have visible only RAM content instead ROM content.
You have to modify the ROM to change the meaning of bank 15, if that's what you want. Are you attempting to run the ROM code from RAM?
Here's also Q2: how is location $0000 and $0001 different to C64? I know their function, but need compare from any C64 user.
Quite different. Location 0 are data direction registers on both machines but the meaning of the bits are different because location 1 is different. C64: bit 0-2: Select RAM/ROM configuration (corresponds to the MMU on the C128) bit 3-5: Cassette control C128: bit 0-1: Color memory bank bit 2: Character set enable bit 3-5: Cassette control bit 6: CAPS lock key The only thing that matches is bit 3-5. |
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Post by mirkosoft on Nov 24, 2019 13:05:56 GMT
Yes I want to run RAM code instead of ROM.
Miro
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Post by oziphantom on Nov 25, 2019 9:52:16 GMT
you can bank out lo BASIC ROM, hi BASIC ROM, and KERNAL as you please. you can get a full 64K of RAM as per 64 if you want. You can then drop in Shared RAM to also see parts of the upper bank into the lower bank. I use
C128_MMU_FIELDS .block
RAM_BANK_3 = $C0
RAM_BANK_2 = $80
RAM_BANK_1 = $40
RAM_BANK_0 = $00
ROM_HI_RAM = $30
ROM_HI_EXT = $20
ROM_HI_INT = $10
ROM_HI_SYSTEM = $00
ROM_MID_RAM = $0C
ROM_MID_EXT = $08
ROM_MID_INT = $04
ROM_MID_SYSTEM = $00
ROM_LO_RAM = $02
ROM_LO_SYSTEM = $00
IO_IN = $00
IO_OUT = $01
.bendTo which then I have defined
PureRAM .macro
lda #C128_MMU_FIELDS.RAM_BANK_0|C128_MMU_FIELDS.ROM_HI_RAM|C128_MMU_FIELDS.ROM_MID_RAM|C128_MMU_FIELDS.ROM_LO_RAM|C128_MMU_FIELDS.IO_OUT
sta $ff00
.endmThis is for a full 64K of RAM in Bank 0
For RAM + IO
JustIO .macro
lda #C128_MMU_FIELDS.RAM_BANK_0|C128_MMU_FIELDS.ROM_HI_RAM|C128_MMU_FIELDS.ROM_MID_RAM|C128_MMU_FIELDS.ROM_LO_RAM|C128_MMU_FIELDS.IO_IN
sta $ff00
.endm
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Post by mirkosoft on Nov 25, 2019 23:31:06 GMT
You forgot main problem - I need to have visible RAM also in bank 15 or others.
$ff00 is the bankswitching config location and when I configure it, all accesses to it, changes the config.
I know that I can see whole RAM by these configs, I can see what I want but - anytime writing to $ff00 changes that config.
Miro
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Post by bjonte on Nov 26, 2019 6:15:43 GMT
Since the ROM decides what ”bank 15” means you have to change the ROM to change the meaning of it. My guess is that there is a table somewhere with values for $ff00 for all bank configurations.
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Post by oziphantom on Nov 26, 2019 6:56:47 GMT
The KERNAL/EDITOR/BASIC assumes the PCR registers are not changed, so you can do some mods that way. However BANK 15 means BANK 15 and that means the ROMs are enabled. If you change BANK 15 to disable ROMs its going to break things.Also the KERNAL doesn't use any of the features of the MMU, so when an IRQ fires or something else happens it will force FF00 to 0 for its code, so IRQs and the like will need to still be in "ALL ROM" mode.
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Post by mirkosoft on Nov 26, 2019 23:10:37 GMT
I know that - but what I want really to do:
I modified sources from author of Soft-Kernal for C64 (author provided me sources) - this I changed that it can change Kernal and also Basic - original not.
It uses switching ROM and I have JiffyDOS in C64 mode without problem, only load program and run.
Basic - I found not yet any existing Basic version which is placed in Basic area, so I try to made my own changes and then create Windows application to create user's mixed Kernals and Basic into single PRG file.
Anything similar I want to do for C128 - but here is problem bankswitching.
For now:
1. I want to replace Kernal only - with same as original but placed in RAM, Basic is near impossible to place into RAM, maybe only Basic HI ROM 'cause Basic LO ROM begins at $4000.
2. If it will be success I mod Kernal or replace with JiffyDOS
Purpose: Have custom Kernal without ROM mods in C128 native mode...
Miro
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Post by oziphantom on Nov 27, 2019 5:10:44 GMT
install code in both BANKS, disable the KERNAL on MMU and all the pre config settings. Make sure you patch all the parts of the KERNAL code that would enable the ROM KERNAL directly.
Might be possible to use External ROM, not sure if the KERNAL will let you patch in the identification sequence and still work.
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Post by mirkosoft on Nov 28, 2019 0:51:58 GMT
Ok, I try, later report.
Miro
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