Converting a game to ROM - and LOTS of ROM files inside!

[arnoldemu]

The "Firmware Guide" claims &b8da->&b8f8 hold the IY value for each ROM. There is space here in CPC6128 for 16 roms, 8 for 464.

What happens in firmware 3.1 where it supports more or in the rom that extends the range up to 32?

Also where is the rom chaining information stored (rom select + next rom in list)

So where exactly is the information stored. I am guessing because if it's in a fixed size buffer it may be running out.

I think this may be why mr_lou is seeing problems?

[TFM]

Maybe. on the other hand once I had 27 ROMs installed without a problem.

Problems usually make Utopia and different DOS ROMs at the same time. Also the AlphaROM is not compatible to everything.

The Games competition ROMs seem all to work fine. If I have some time (during the next month), I'll take a look at it.

@Mr_Lou: Can you provide a screen dump or list of ROMs which cause problems? So the error could be reproduced.

[redbox]

What happens in firmware 3.1 where it supports more or in the rom that extends the range up to 32?

Nothing happens, the buffer is the same size as the original OS AFAIK.  Same with my MegaFlash version of the Plus cartridge.

So I think you may well be onto something here...

[ralferoo]

Also where is the rom chaining information stored (rom select + next rom in list)

In (#b8d3) (6128), there is a pointer to the most recent RSX block registered.
The first two bytes are the address of the next RSX block, the second two bytes are the "RSX address".
If the RSX address has a zero high-byte, it is a ROM RSX table and the low-byte is the ROM select byte and the table is at #c004. Otherwise, it's a RAM RSX table.

This is exactly what the 4 bytes that gets used per ROM is for.

The "Firmware Guide" claims &b8da->&b8f8 hold the IY value for each ROM. There is space here in CPC6128 for 16 roms, 8 for 464.
What happens in firmware 3.1 where it supports more or in the rom that extends the range up to 32?
So where exactly is the information stored. I am guessing because if it's in a fixed size buffer it may be running out.

You're totally correct, there does appear to have a fixed size block for the  IY table for each ROM:

Code: [Select]

034c 23        inc     hl
034d eb        ex      de,hl
034e 21dab8    ld      hl,$b8da        ; the ROM table
0351 ed4bd6b8  ld      bc,($b8d6)    ; the currently active ROM (as we're probing them all in sequence this will be set)
0355 0600      ld      b,$00
0357 09        add     hl,bc
0358 09        add     hl,bc          ; #B8DA + 2*(#B8D6)
0359 73        ld      (hl),e
035a 23        inc     hl
035b 72        ld      (hl),d          ; store IY (which is HL+1 as returned from the ROM)
035c 21fcff    ld      hl,$fffc
035f 19        add     hl,de          ; reserve the 4 bytes for the RSX chain
0360 cda002    call    $02a0                    ; KL LOG EXT

Also, this supports the theory of the fixed-size:

Code: [Select]

;; rom select below 16 (max for firmware 1.1)?
048c fe10      cp      $10         
048e 300f      jr      nc,$049f   

;; 16-bit table at &b8da
0490 87        add     a,a
0491 c6da      add     a,$da
0493 6f        ld      l,a
0494 ceb8      adc     a,$b8
0496 95        sub     l
0497 67        ld      h,a

So, in summary, I'd say if someone is using the standard firmware, there should be no issue. With a modified firmware to accept more than 16 ROMs, this table will need to be moved somewhere else. I'd suggest the following additional patches (untested though):

Code: [Select]

0089 21ffab    ld      hl,$abff      ; decrease this by number of ROMs, so 32 -> #abdf
...
034e 21dab8    ld      hl,$b8da      ; change to #abe0 for 32 ROMs
...
0491 c6da      add     a,$da         ; change to #e0 for 32 ROMS
0493 6f        ld      l,a
0494 ceb8      adc     a,$b8         ; change to #ab

So,

Code: [Select]

008a df
008b ae
034f e0
0350 ab
0492 e0
0495 ab

This should work reliably as nothing else uses these table, but at the expense of another 64 bytes of RAM...

[ralferoo]

Maybe. on the other hand once I had 27 ROMs installed without a problem.

This table will only be updated for background ROMs (i.e. with RSXes). Foreground ROMs take over the system and so don't need the IY value and extension ROMs aren't scanned at all.

So, if you only put extension ROMs in the top 16 slots, you'd not experience any corruption.

[redbox]

So, in summary, I'd say if someone is using the standard firmware, there should be no issue. With a modified firmware to accept more than 16 ROMs, this table will need to be moved somewhere else. I'd suggest the following additional patches (untested though):

Excellent work, I shall test with my DIY Plus Cartridge as soon as I get a chance.

[mr_lou]

@Mr_Lou: Can you provide a screen dump or list of ROMs which cause problems? So the error could be reproduced.

When I find the time, I will try from scratch, installing one game at a time, and testing all games after each installation, and describe everything, and then attach a zip with the ROM files I used.
But this socalled adult life is a real time waster. You have to do boring stuff like work and such, so it'll be a while before I have the time.

[SuTeKH/Epyteor]

My, my... this is turning into an interesting thread.

[arnoldemu]

This table will only be updated for background ROMs (i.e. with RSXes). Foreground ROMs take over the system and so don't need the IY value and extension ROMs aren't scanned at all.

So, if you only put extension ROMs in the top 16 slots, you'd not experience any corruption.

I also believe that extension roms will not be registered here.

Question:

The "booster" rom uses the standard firmware. So does the booster rom allocate some memory to fit the additional information in, or if used with a standard OS does it also cause problems?

[redbox]

The "booster" rom uses the standard firmware. So does the booster rom allocate some memory to fit the additional information in, or if used with a standard OS does it also cause problems?

The Booster ROM just patches the firmware (by patching the jump lock).  It's a very simple patch and doesn't patch the RST routine in the OS ROM which is what leads to it's instability.

[arnoldemu]

The Booster ROM just patches the firmware (by patching the jump lock).  It's a very simple patch and doesn't patch the RST routine in the OS ROM which is what leads to it's instability.

So it allows the firmware to register roms above 16, it'll then try and do that and corrupt memory.
Nice. I think there is some space in there anyway, so you'd get away with a bit.

[TFM]

...But this so called adult life is a real time waster. You have to do boring stuff like work and such, so it'll be a while before I have the time.

Tell me about it    Never mind, as soon as you're ready I'll take a look at it. 

[SuTeKH/Epyteor]

(Obvious trolls are obvious)

Starting the FreeScape 3D collection we have |DARKSIDE and |DRILLER. Both of which happily fit in 2 ROMs per game... the other FreeScape 3D titles (CASTLE MASTER, THE CRYPT, TOTAL ECLIPSE, TOTAL ECLIPSE TRAINER, SPHINX JINX and the 3D INTRODUCTION GAME) are a little more irritating and will require 3 ROMs to house them... I'll do that whenever I get time!

EDIT: Someone mentioned Melvyn Wright in a thread a few months back, and that prompted me to convert a few of the Firebird music-load games (from existing hacks). First on my list was the brilliant, but feck-off hard, |DRUID... complete with loading music!

EDIT: Slight leftfield turn now; Arkos & Overlander's |DTC demo. Wobbler meets plasma meets scroller to ZX music... followed by ruptured logo to the Spitting Images theme tune (AY'd by David Whittaker for the game of the same name).

EDIT: Finally, ROMANTIC ROBOT's mega-huge maze race; |WRIGGLERRR. The name has two extra Rs in it as there is already a WRIGGLER ROM in the collection and this will prevent any issues if both games are installed.

[dcdrac]

will these roms work in the new Xmem and if so how doi transfer them?

[SyX]

will these roms work in the new Xmem and if so how doi transfer them?

Of course, X-Mem brings the firmware 3.14, that was fixed along time ago. In our case we use the range $BE00-$BE3F  for storage the new pointer table.

With respect to transfer, use your favourite way, using a minibooster or put the roms in a 3" 1/2 or 3" disk, etc...

[Gryzor]

Freescape in ROM? Niiiiiiiice!

[redbox]

Firmware 3.14, that was fixed along time ago. In our case we use the range $BE00-$BE3F  for storage the new pointer table.

I must have missed this... do you have a download link?

[CraigsBar]

The Freescape games from ROM are great, thanks.


On a separate note has anyone managed to get the ROM version of Head over Heals to actually run?


I get a screen of garbage on both my 6128plus and Schneider CPC 6128.


On WinAPE it hangs and on JavaCPC it triggers a reset.


I have downloaded the file many many times and copied the rom images to the Symbiface via the HxC and by pulling the HDD the result is always the same, and only with these roms.


Do these ROMS have specific slots, in which case what are they or are they just fubar or have I lost the plot, and this is a sign that I should have 1 more go on Driller, Harvey Headbanger or Chuckie Egg.


Kind Regards


Craig

[CraigsBar]

I must have missed this... do you have a download link?

As I understand it is not generally available yet, and requires a X-Mem.


Hopefully soon


Regards


Craig

[IanS]

On a separate note has anyone managed to get the ROM version of Head over Heals to actually run?


I get a screen of garbage on both my 6128plus and Schneider CPC 6128.

The head over heels roms are expecting the roms to be in position 9,16 and 17.
If you want to relocate them, you need to modify bytes &c05b (rom 1), &c06b (rom 2) & &c07b (rom 3) of rom 1.

[CraigsBar]

The head over heels roms are expecting the roms to be in position 9,16 and 17.
If you want to relocate them, you need to modify bytes &c05b (rom 1), &c06b (rom 2) & &c07b (rom 3) of rom 1.

Perfect, thanks. Guess what I'll be doing tomorrow

[MiguelSky]

the other FreeScape 3D titles (CASTLE MASTER, THE CRYPT, TOTAL ECLIPSE, TOTAL ECLIPSE TRAINER, SPHINX JINX and the 3D INTRODUCTION GAME)

Don't forget Ciudadela Fantasma and A Chance in Hell !! 

[Devilmarkus]

The head over heels roms are expecting the roms to be in position 9,16 and 17.
If you want to relocate them, you need to modify bytes &c05b (rom 1), &c06b (rom 2) & &c07b (rom 3) of rom 1.

Confirmed:
 [ Invalid Attachment ]

Thankyou for this information, as there was no readme included...

[SyX]

As I understand it is not generally available yet, and requires a X-Mem.


Hopefully soon

That must be an urban legend , you can download it from the X-Mem page, everything is available there... aside the ungrateful nazi pirates and spanerds buccaneers clonning Bryce, Pulkomandy, TotO and any interesting new boards.

With respect to the HoH roms, it was one of the first roms, with Bombjack, that i made for the Megaflash and by then, before the lower rom expansions era , the idea was put all the extra weight in rom numbers >15 as FutureOS always did and TFM always recommend

[SyX]

Thankyou for this information, as there was no readme included...

No readme? 

And the Bomb Jack readme, just in case