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Atari 800XL - no internal basic

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Right now i'm feeling pretty proud of myself :-)

 

I know this will be no big deal to most of the forum, but what I find interesting is I did post this question some years back (maybe 10 years - might have been a different Atari forum - I dont recall) and never got a usable answer:

 

What I wanted to do was to disable the internal BASIC on the 800XL permanently, or at a minimum reverse the OPTION key so that BASIC was off by default.

 

Thanks to Bob Woolley's 1200XL PBI mod, I was able to figure out that if I remove the BASIC chip altogether (U4) and then lift pin 18 of the MMU (U3) the 800XL boots up to self-test and I no longer need to hold down OPTION to load software. I have tested this with a bunch of 48K and 64K games and so far everything works. Cartridge BASIC works for anything that does need BASIC. I am waiting to figure out what I have broken!

 

Anyway, thought I'd pass that on in case any other 800XL owners wanted the same feature.

 

And if anyone who knows what they're doing can tell me if I've broken something doing this i would appreciate the insights.

 

Cheers.

 

 

Graham

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Right now i'm feeling pretty proud of myself :-)

 

I know this will be no big deal to most of the forum, but what I find interesting is I did post this question some years back (maybe 10 years - might have been a different Atari forum - I dont recall) and never got a usable answer:

 

What I wanted to do was to disable the internal BASIC on the 800XL permanently, or at a minimum reverse the OPTION key so that BASIC was off by default.

 

Thanks to Bob Woolley's 1200XL PBI mod, I was able to figure out that if I remove the BASIC chip altogether (U4) and then lift pin 18 of the MMU (U3) the 800XL boots up to self-test and I no longer need to hold down OPTION to load software. I have tested this with a bunch of 48K and 64K games and so far everything works. Cartridge BASIC works for anything that does need BASIC. I am waiting to figure out what I have broken!

 

Anyway, thought I'd pass that on in case any other 800XL owners wanted the same feature.

 

And if anyone who knows what they're doing can tell me if I've broken something doing this i would appreciate the insights.

 

Cheers.

 

 

Graham

 

I'm not a hardware GURU, but I reccomend you the 32in1 OS from Atarimax. Almost plug&play. It contains many OS revisions, one of them is with reversed OPTION key handling on boot: loads basic only if you press the OPTION key. You can change which OS to boot on cold reset. Very useful and 100% compatible.

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... if I remove the BASIC chip altogether (U4) and then lift pin 18 of the MMU (U3) the 800XL boots up to self-test and I no longer need to hold down OPTION to load software.

That works because pin 18 has a weak internal pull-up that keeps the -BE (BASIC Enable) signal high, or inactive. But it could pick up electrical noise and cause mysterious crashes.

 

A better solution is to reconnect pin 18 and disconnect the signal at the other end, pin 11 of U23, the PIA. That way, R85 can pull the signal up strongly.

 

You don't need to remove the BASIC ROM - it should never get selected. If you want, you can remove both old BASIC ROMs from your cartridge and put the XL BASIC ROM into either one of the sockets. Then you'll have the newer BASIC in your cart.

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A better solution is to reconnect pin 18 and disconnect the signal at the other end, pin 11 of U23, the PIA. That way, R85 can pull the signal up strongly.

ACK, this is a better solution. If you like you can also extend this a little bit:

 

I added a switch to my Ataris so that I could select between Basic permanently off, permanently on (this is handy if you use an "oldrunner OS" and still want Basic to be present) and normal mode (selectable by PIA).

 

All you need is a simple single pole dual throw switch with neutral (off) position in the center. Lift up PIA pin 11, connect this pin to one pole of the switch, connect the middle pin of the switch to the socket of the PIA, pin 11, and the other pole to ground.

 

So, in one position the basic enable signal to the MMU is connected to the PIA output and software controllable, just like the in the stock Atari. In the other position it is tied to ground and is permanently enabled. If you set the switch to the center "off" position, no connection is made and the pullup resistor R85 (in the 800XL) pulls the signal up to +5V and disables Basic.

 

so long,

 

Hias

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... if I remove the BASIC chip altogether (U4) and then lift pin 18 of the MMU (U3) the 800XL boots up to self-test and I no longer need to hold down OPTION to load software.

That works because pin 18 has a weak internal pull-up that keeps the -BE (BASIC Enable) signal high, or inactive. But it could pick up electrical noise and cause mysterious crashes.

 

A better solution is to reconnect pin 18 and disconnect the signal at the other end, pin 11 of U23, the PIA. That way, R85 can pull the signal up strongly.

 

You don't need to remove the BASIC ROM - it should never get selected. If you want, you can remove both old BASIC ROMs from your cartridge and put the XL BASIC ROM into either one of the sockets. Then you'll have the newer BASIC in your cart.

 

So either ROM socket of the XL series takes a 27256 EPROM? That would mean you can put in any ROM instead of BASIC into the Atari memory $8000...$BFFF area and use OPTION to disable it.

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If you want, you can remove both old BASIC ROMs from your cartridge and put the XL BASIC ROM into either one of the sockets. Then you'll have the newer BASIC in your cart.

So either ROM socket of the XL series takes a 27256 EPROM? That would mean you can put in any ROM instead of BASIC into the Atari memory $8000...$BFFF area and use OPTION to disable it.

NO! The BASIC ROM has 24 pins - not 27256 compatible.

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If you want, you can remove both old BASIC ROMs from your cartridge and put the XL BASIC ROM into either one of the sockets. Then you'll have the newer BASIC in your cart.

So either ROM socket of the XL series takes a 27256 EPROM? That would mean you can put in any ROM instead of BASIC into the Atari memory $8000...$BFFF area and use OPTION to disable it.

NO! The BASIC ROM has 24 pins - not 27256 compatible.

 

I guess you were talking about ROM sockets within the cartridge not the ROM sockets on the motherboard. The ROM socket (at least one of them) on the XL motherboard is 28 pins. I thought you were stating you could take both ROMs out of the XL motherboard and replace them with one ROM containing BASIC+OS ROM which would imply that it takes up to 32KByte (256kbit) ROM.

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... if I remove the BASIC chip altogether (U4) and then lift pin 18 of the MMU (U3) the 800XL boots up to self-test and I no longer need to hold down OPTION to load software.

That works because pin 18 has a weak internal pull-up that keeps the -BE (BASIC Enable) signal high, or inactive. But it could pick up electrical noise and cause mysterious crashes.

 

A better solution is to reconnect pin 18 and disconnect the signal at the other end, pin 11 of U23, the PIA. That way, R85 can pull the signal up strongly.

 

You don't need to remove the BASIC ROM - it should never get selected. If you want, you can remove both old BASIC ROMs from your cartridge and put the XL BASIC ROM into either one of the sockets. Then you'll have the newer BASIC in your cart.

 

 

Claus,

 

Thanks for the insights. I am planning to install a Wizztronics 256K upgrade this weekend, so I'll switch to your recommendation with the PIA instead of the MMU.

 

And I think I will take your suggestion of installing the Rev C BASIC in one of my Atari BASIC cartridges, since I think they are both Rev A.

 

I'm just happy to be able to boot game disks on the 800XL without having to hold down OPTION every time!

 

Cheers.

 

 

Graham

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Will this line of thought work on the 130XE?

 

A better solution is to reconnect pin 18 and disconnect the signal at the other end, pin 11 of U23, the PIA. That way, R85 can pull the signal up strongly.

ACK, this is a better solution. If you like you can also extend this a little bit:

 

I added a switch to my Ataris so that I could select between Basic permanently off, permanently on (this is handy if you use an "oldrunner OS" and still want Basic to be present) and normal mode (selectable by PIA).

 

All you need is a simple single pole dual throw switch with neutral (off) position in the center. Lift up PIA pin 11, connect this pin to one pole of the switch, connect the middle pin of the switch to the socket of the PIA, pin 11, and the other pole to ground.

 

So, in one position the basic enable signal to the MMU is connected to the PIA output and software controllable, just like the in the stock Atari. In the other position it is tied to ground and is permanently enabled. If you set the switch to the center "off" position, no connection is made and the pullup resistor R85 (in the 800XL) pulls the signal up to +5V and disables Basic.

 

so long,

 

Hias

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I'm just happy to be able to boot game disks on the 800XL without having to hold down OPTION every time!

You probably know this but MyPicoDOS lets you boot a menu without holding Option and runs most programs, Basic or not... I guess like me you have shed-loads of old disks using other menus etc :ponder:

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Will this line of thought work on the 130XE?

Yes, this should also work on the 130XE. I haven't tried it myself (I prefer XLs), but this part of the schematic is the same for 600/800XL and 65/130/800XE.

 

so long,

 

Hias

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