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Nezgar

Game ROMs that work in place of BASIC

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So I've been playing with 2364 adapters from Retro Innovations in an 800XL. http://store.go4retro.com/2364-adapter/With no jumpers or resistors, it works fine with a 27C64 EPROM for a simple upgrade to Rev C Basic while leaving the motherboard's original 24 pin socket in place.

Next, I added the resistors, and burned 4 appended 8K ROMS a 27C256 starting with Atari BASIC Rev C, and Altirra BASIC 1.88, and then for fun picked the 2nd two 8K roms at random Frogger & Gyruss. Only Gyruss didn't work of the 4. Switchable BASIC ROM is kinda cool :). Then I tried again with Star Raiders instead of Gyruss and that doesn't work either. Any particular reason these ROM's don't work as a BASIC replacement?

Any suggestions of other games (or interesting tools/utilities) that work as a BASIC ROM replacement without trying each manually? (I presume the XEGS Missile Command is an obvious contender)

Realistically, I'll probably end up wiring just 1 SPDT switch, so only 3 of the slots would be accessible anyway.

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I’ve used a lot of 8K game roms as “alternate BASIC’s” so to speak in the BASIC slots of my U1MB equipped machines. I don’t remember any of them not working. I will check Star Raiders and Gyruss tonight. Pretty sure I’ve tried them successfully in the past but perhaps I misremember.

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Hmm. It's possible that it's just a particular slot # on my adapter is borked if I damaged a resistor connected to the select lines while soldering or something, I'll have to test more later, i don't remember if it was the same slot that didn't work in both burned attempts.

Edited by Nezgar

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I remember putting a Galaxian rom into my 600XL years ago and it worked fine.

 

You should be able to put a 16K rom in as long as you connect the extra address line.

 

One of these days I want to try putting 2 different games in my XE Game System.

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So I've been playing with 2364 adapters from Retro Innovations in an 800XL. http://store.go4retro.com/2364-adapter/With no jumpers or resistors, it works fine with a 27C64 EPROM for a simple upgrade to Rev C Basic while leaving the motherboard's original 24 pin socket in place.

 

Next, I added the resistors, and burned 4 appended 8K ROMS a 27C256 starting with Atari BASIC Rev C, and Altirra BASIC 1.88,

 

 

Hmmm, really Altirra Basic 1.88 ?!? The newest one I have is AltBas 1.55, where can I find the newer version ? (Downloaded Altirra Beta 3.10 test 30 and the Additions.ATR still contained V1.55...) Or was this just a typo ?

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Haha ya, whatever comes with altirra 3.0 export lol. I admit I guessed (wrongly). :)

Edited by Nezgar

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I’ve used a lot of 8K game roms as “alternate BASIC’s” so to speak in the BASIC slots of my U1MB equipped machines. I don’t remember any of them not working. I will check Star Raiders and Gyruss tonight. Pretty sure I’ve tried them successfully in the past but perhaps I misremember.

 

Star Raiders and Gyruss take 16 KB. That´s impossible as a replacement for the BASIC-ROM. The MMU decodes only 8 KByte address range when PB1 is set to low (BASIC enabled) in the area of $A000-$BFFF. Even when you add the needed A13 addressline and use a 28128 or bigger EPROM, the system always only would access the 8 KByte.

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The ROM files for Star Raiders and Gyruss are only 8192 bytes - do you mean they normally sit in the lower half of a 16KB cart space? That would explain why it doesn't work since BASIC sits in the upper range ($A000-BFFF as you mention)

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The ROM files for Star Raiders and Gyruss are only 8192 bytes - do you mean they normally sit in the lower half of a 16KB cart space? That would explain why it doesn't work since BASIC sits in the upper range ($A000-BFFF as you mention)

 

Hmm. Regarding Gyruss I´m pretty sure that only a 16 KB version exists. The unpatched version makes trouble with VBXE (black screen), but without this point it´s an absolute 08/15 standard 16 KB game cartridge. Star Raiders... I know only "Star Raiders II" (sometimes called "The last starfighter?" I´m not sure...), this is a 16 KB ROM, too.

 

When the game was originally 8 KB, then it should run as a BASIC replacement.

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Interesting, I just checked atarimania, and you're right it's a 16KB ROM. So this 8KB file I used is strange. Will have to look at it with hex editor to see what it is actually.

 

Star Raiders (original version, not II) is what I was trying - 8KB on atarimania.

Edited by Nezgar

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I compared my Star Raiders ROM same against the one from AtariMania, and it matches, so maybe it's something to do with the way the real Star Raiders cart being a 'diagnostic cart' - maybe is initializing differently this way. (Not taking control before the OS)

 

I also just confirmed that I used different slots each burn.. First time Gyruss didn't work in slot 3, this time Altirra BASIC is in that slot and works. Previously Altirra Basic was in my 3rd slot and worked, where Star Raiders was the 2nd round and doesn't work. So... this means it should be just the the ROM images themselves to investigate.

 

The 8KB 'Gyruss' mystery ROM I used is significantly different from the 16KB ROM on AtariMania - it's not even just the lower or upper half. No idea where I got it.. attaching if anyone's interested in analyzing it :)

Gyruss-Mystery8KB.rom

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Yeah, I checked file sizes when I got home awhile ago and Gyruss is definitely a 16KB file so clearly I mis-remembered.

 

For what it's worth, currently the "XEGS Game" slots in my Ultimate 1MB-equipped 1088XEL are Pac-Mac, Galaxian, Missile Command and Star Raiders (which just gives a black screen). I remember now figuring out Star Raiders doesn't work and I just never quite got around to flashing the slot with a different game. :)

Edited by DrVenkman

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Excellent, so we have confirmation of no go for Star Raiders on your setup too. I also just get black screen. Thanks! it's just a little slower to try various titles with a UV eprom. :)

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I compared my Star Raiders ROM same against the one from AtariMania, and it matches, so maybe it's something to do with the way the real Star Raiders cart being a 'diagnostic cart' - maybe is initializing differently this way. (Not taking control before the OS)

The OS indeed cannot run the internal ROM as a diagnostic cartridge. The "diagnostic cartridge" flag is examined only when the TRIG3 register is set to 1, which indicates a real cartridge being inserted. Enabling internal BASIC does not change TRIG3, so the diagnostic flag is never checked. As a result, the internal ROM is always run as a non-diagnostic cartridge. (See the PMI routine, offset C471 in OS rev. 2.)

 

But this issue alone would not be a problem in case of "Star Raiders" - this game runs correctly even if the "diagnostic cartridge" flag is disabled. The actual culprit is that, being a diagnostic cartridge, "Star Raiders" must initialize all hardware by itself. In the process, it writes $00 to all registers of PIA, including PBCTL and PORTB, disabling the internal BASIC. (See the loop at $A162.) So, when run as an internal ROM, Star Raiders disables itself.

 

The 8KB 'Gyruss' mystery ROM I used is significantly different from the 16KB ROM on AtariMania - it's not even just the lower or upper half. No idea where I got it.. attaching if anyone's interested in analyzing it :)

It is indeed a Gyruss ROM... for the PAL Atari 2600. Edited by Kr0tki
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Star Raiders would need some work.

First up a diag mode cart simply won't work internally. At powerup the PIA outputs all default to 1 which mean OS switched in, Basic and SelfTest out, RAM at default configuration for >= 128K systems.

 

Fixing the diag mode thing would likely be easy - just move the contents of $BFFE-F to $BFFA-B.

But SR also does it's own system initialization which involves clearing harware registers. You'd probably need to patch the Rom to remove the writes to PIA - just put 3 x NOPs at $A172.

 

It's also possible it clears page 2-3 at some stage which could also cause problems. The easy way to test diag mode carts is to just patch the Roms as described for the run vector then test in emulation.

 

An alternative to doing all this could be to just aquire the executable version of 8K cartridges which all run Ram-based then rip the relevant section to use as your Rom, and ensure the vectors are correct. The easy way there would be to just dump out the 8K section while it's running in an emulator.

Edited by Rybags
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Hello,

 

I've been playing with BASIC replacement roms for quite a few years. Star Raiders and River Raid are diagnostic carts that have been fixed for XL machines. They are included in the .zip file that I attached that has 128 8K roms. I test the roms with Altirra and all these work with the emulator but Twin Pack Sinker + Teaser doesn't work in the BASIC slot?? Included is a link to an old discussion about BASIC replacements.

 

http://atariage.com/forums/topic/110394-basic-rom-replacement-eproms/?hl=redman&do=findComment&comment=1338759

 

8kroms.zip

 

Redman

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Same problem as Star Raiders, Twin Pack Sinker + Teaser writes to PORTB on start and banks itself out when run as an internal BASIC.

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Thanks everybody! It's great learning this stuff from the community, and that the knowledge is out there - less reinventing of the wheel. I suspected it was something to do with the Diagnostic mode of that game in the first place, but it's interesting to learn exactly how and why. Banking itself out is a pretty quick suicide. :)

 

Thanks redman for the pointer to the previous thread and curated list of 8K ROM's, that's a big time saver. Cool to see the patched River Raid in that thread. I presume the star_raiders_xlxefix.rom in the ZIP has also already been patched to work as a BASIC replacement.

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and yes I can now report yes star_raiders_xlxefix.rom from radman's 8kroms.zip works :-D :thumbsup:

Edited by Nezgar
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I replace the BASIC chip with a 27C801 1 mb that holds 128 8K images. It's hard and very time consuming to find a nice collection of 128 interesting programs. I've attached 2 more images. I found both of them on AtariOnline a while back. Beatka is something else! I wonder if all the flashing has to do with it being meant for PAL?

 

More8K.zip

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Why not just treat a 1 Meg Rom like a big disk image? Then do a binary loader and device handler and a menu that just downloads the games to Ram?

You could also run the images through a compressor which would give about 50% more capacity.

(in theory the AtariMax software could be patched to work with a bankable Rom instead of it's EEPROM)

Edited by Rybags
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Yeah, 128 8K ROM's is overkill, how would you even select between them without a software solution..

 

So back to my simple 4 bank 27C256, I can easily switch between 3 of the 4 with a single 3-Pin 3 Position ON-OFF-ON aka SPDT switch. Whats a nice way to select between more banks, ie all 8 of a 27C512 without a row of SPDT switches? I'm thinking a rotary switch of some sort.

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I had some 16 position thumbwheel switches I once used for a DIY 16 in one OS. The old pushbutton SCSI select switches from the back of old drive enclosures are nice too.

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