New Twist on a Very Good 1200XL Upgrade

[+Guitarman]

Anyone who has a 1200XL has probably seen, or installed, at least part of the Bob Woolley PBI upgrade, mainly the XL OS and built in BASIC. Here is a tweak to the old instructions that will allow you to use a 2764 eprom with BASIC C written to it instead of the Atari BASIC Rom. This tweak is kind of a marriage of Bob Woolley's PBI instructions and Atarimax's 32in1 OS 1200XL installation instructions. The main difference is the Atari rom is 24pin and a 2764 is 28. No problem as the 1200XL mainboard has room for 28pin sockets in the OS locations.

 

Follow the PBI upgrade instructions for the OS chip install with the exception of replacing BOTH 24pin sockets with 28pin. When you get to the jumper settings, instead of keeping jumpers W11, W12 and W9, keep W11, W12 and W13. Jumper W6 still gets removed.

 

To add BASIC, program a 2764 eprom with BASIC RevC code, lift or cut off pin 26 and insert the programmed 2764 into the 28pin socket above the OS chip. Unlike the PBI upgrade, there are no other wires coming off the BASIC chip. Connect the last wire from pin 18 of U14 (MMU) to pin 11 of U23 (PIA). Upgrade complete!!

 

Here are the modified instructions. I am only including the OS/BASIC part of the upgrade. If you choose to do the remainder of the PBI mod, follow the remainder of the instructions located here.

 

Condensed OS/BASIC upgrade instructions for 1200XL (originally posted by Bob Woolley)

Modified by Adam Brannon using procedures used in AtariMax’s 32in1 OS Upgrade

 

Parts needed

1-XL/XE OS (CO61598B)

1-XL/XE MMU (CO61618)

1-2764 EPROM (Programmed with BASIC RevC)

2-28 pin sockets

2- 5” length wire (wire wrap type)

 

1. Remove the current 1200XL OS roms at U12 & U13

2. Desolder and remove 24 pin sockets at U12 & U13

3. Make sure all 28 pin sites at U12 & U13 are cleared of solder. Install and solder 28 pin sockets at U12 & U13

4. Remove the jumper at W6. Set aside for later.

5. Remove current MMU at U14 (CO60609). Replace with XL/XE MMU (CO61618)

6. Remove all jumpers except W11, W12 and W13

7. Solder wire from pin 18 of U14 (MMU) to pin 11 of U23 (PIA)

8. Solder wire from pin 23 of U21 (CPU) to the top pad of W6

9. Install XL/XE OS at U13

10. Install programmed 2764 at U12. Make sure pin 26 is lifted or removed.

11. Bonus Mod!! Locate R63 near SIO connector. Remove R63 and replace with jumper removed from W6. You now have +5 to the SIO for using SIO powered hardware not normally compatible with the 1200XL.

 

Put everything back together and test by booting without a drive attached. If the upgrade went right, you should see the READY prompt. Type PRINT PEEK(43234) and press return. A value of ‘234’ should be returned. This tells you that the revision of BASIC is C.

 

You now have a fully 600XL/800XL compatible 1200XL with built in BASIC. Enjoy!!

[Gunstar]

I presume that one could also have something else OTHER than Basic on those eproms too, right? Like another language or game/program that would automatically boot up like BASIC and be disabled with the OPTION key? Sort of how the XEGS has Missle Command on internal rom.

[+Guitarman]

I would assume so, as long as it is only a 8k rom size, unless a bigger eprom can go there without more modification.

[Rybags]

"Diagnostic mode" ROMs such as Star Raiders might have a problem.

 

Normally the OS immediately checks for and runs a diag type cart, but will do a JSR through the $BFFA with the "E:" device opened for a game which replaces the BASIC ROM.

 

The OS won't run a resident ROM immediately because it checks the TRIG line which signals that a cartridge is present.

 

Best way to check a game would be to just run a test in the emulator first (just point BASIC to the ROM).

Edited April 10, 2007 by Rybags

[Beetle]

I have Basic, Galaxian and two extended RAM test tools in a 27C128 EPROM. It works good so far, but the computer will only boot with BASIC or Galaxian selected. I don't know why the others don't get disabled when booting with option pressed.

[Rybags]

Which OS is it running though?

 

Any chance you can upload the other ROMs?

 

As I said earlier, you don't get quite the same behaviour if the onboard ROM is a diag type ROM as compared to having it on cartridge - some might not be happy that the system is already mostly initialized once they gain control.

 

Unsure what the 1200XL OS does, as by default it doesn't have inbuilt ROM other than the OS.

 

Ed: Looks like the 1200XL has the same logic to check for a cartridge (TRIG2).

Edited April 10, 2007 by Rybags

[re-atari]

I have Basic, Galaxian and two extended RAM test tools in a 27C128 EPROM. It works good so far, but the computer will only boot with BASIC or Galaxian selected. I don't know why the others don't get disabled when booting with option pressed.

Are you sure about the type of eprom? A 27128 is 16K, which would only give room to store Basic and Galaxian (AFAIK both are 8K), there's no space for anything else. I presume you use a switch and pull-up resistor on A13 to select between them?

Not really an answer to your question, I have to admit...

 

re-atari

[Beetle]

I pulled the Label and you are right, its a 27C256

If you like too, i can read out the Eprom.

Edited April 10, 2007 by Beetle

[Gunstar]

I was thinking it might be cool to have an assembly language or Turbo Basic on ROM OS instead of Atari Basic. Could this be possible? I don't know what languages take how much rom space (e.g. 8-16K) or if it would be possible at all for something like Turbo Basic to be put on rom, but what about MAC/65 or something? Does it HAVE to be limited to 8k or 16k if you have a larger capacity eprom that would work there? Is it possible, for example, that maybe a 32K or 64K 28-pin eprom exists that could be used there? I mean, I know anything is really possible, especially with a menu system like APE Warp+ 32-in-1, obviously with 32 OS's there definately more that 8-16k there, but it's swapped in/out I guess (not a programmer so I'm not real familiar with how this stuff works). But everybocy is always talking about getting Bsic REV. C or something in there and I'm not sure why it's a top priority when very few of us normal (non-programming) users actually use Basic. And I'd think a programmer would rather have a built-in Assembly rather than the old Atari Basic. Personally, if I was an avid programmer, I'd rather have something other than Atari Basic built-in and would be satisfied with using a Basic cartridge if Basic is needed.

[Beetle]

I found a TurboDOS modified for 8k cart. Its a nice command line DOS, DOS2.x compatible, 90k to 180k (special 360k version available) I think of replacing one RAM test with that. Turbo Basic is not possible as Basic replacent, since it is bigger than 8k (and it uses RAM under OS as well).

Edited April 10, 2007 by Beetle

[Beetle]

Well, i found out you can actually have TurboBasic internally. But its a bit more of a job than replacing a Rom with an Eprom.

 

 

Have fun,

Beetle

[re-atari]

Well, i found out you can actually have TurboBasic internally. But its a bit more of a job than replacing a Rom with an Eprom.

By the look of it, this is a bankswitching cartridge, although it differs from the OSS carts. The makers must have had access to Frank Ostrowski's source code in order to incorporate a bankswitching format.

Good job, if it works. Do you have the contents of the rom as well?

 

re-atari

Edited April 10, 2007 by re-atari

[Beetle]

Do you have the contents of the rom as well?

 

re-atari

 

i think its in here...

[Gunstar]

It would be cool if someone like AtariMax made and upgrade to go with the 32-in-1 OS, like the 32-in-1, but having all the major Atari languages on it at a touch of a button.

[Shawn Jefferson]

Ideally, I'd like to have the upgrade Gunstar talks about above, but with all versions of Atari Basic (A, B & C), and a built-in DOS (like those insta-dos carts). Most of the time I'd probably have the DOS selected, but you'd still want to have Basic available for the odd program that requries it.

 

Actually, come to think of it, I'd really like to have my MyIDE Image Manager in a basic rom instead. Unfortunately, it's currently too big.

 

I wish I knew more about electronics, I'd try to build it. Is possible to bank switch the basic rom, without interfering with normal cartridge bank switching. I assume (with little knowledge) that you'd want to AND the bit from $D301 that signifies if basic is enabled, and then bank in the next bit of your "basic rom" into cartridge space.

 

Hmm....

[Rybags]

I feel that having all revs of BASIC would be pointless. Rev C is the supposed bug-free one, and they are all functionally the same anyway. I don't know of any software that attempts to utilize the bugs in A/B.

 

Since a switchable ROM for the language would have to be a mod, the best method would probably be to just tap into the cart control ($D5xx) line and use it for bank-selection.

[Shawn Jefferson]

I feel that having all revs of BASIC would be pointless. Rev C is the supposed bug-free one, and they are all functionally the same anyway. I don't know of any software that attempts to utilize the bugs in A/B.

 

Yes, you're probably right, and that's most likely the reason this mod hasn't been done already.

[tjlazer]

I feel that having all revs of BASIC would be pointless. Rev C is the supposed bug-free one, and they are all functionally the same anyway. I don't know of any software that attempts to utilize the bugs in A/B.

 

Yes, you're probably right, and that's most likely the reason this mod hasn't been done already.

 

So basically the 1200XL OS is split into two chips, and with this upgrade you are putting in one Chip as OS and the other chip as Basic, correct? So the MMU chip is absolutely needed for this right? How much are they?

[+Guitarman]

I feel that having all revs of BASIC would be pointless. Rev C is the supposed bug-free one, and they are all functionally the same anyway. I don't know of any software that attempts to utilize the bugs in A/B.

 

Yes, you're probably right, and that's most likely the reason this mod hasn't been done already.

 

So basically the 1200XL OS is split into two chips, and with this upgrade you are putting in one Chip as OS and the other chip as Basic, correct? So the MMU chip is absolutely needed for this right? How much are they?

 

 

Yes, you will need the MMU from a XL/XE system. You can get them from Best.

 

CO61618 (XL / XE Memory Management.) $14.00

[hueyjones70]

Since I don't have EPROM burner, where could I get a 14 pin EPROM with Basic C ?

[ACML]

When you put in the 800XL MMU does the 1200XL L1 and L2 LEDs and F1-F4 keys still function as normal?

[+Nezgar]

Since I don't have EPROM burner, where could I get a 14 pin EPROM with Basic C ?

14 pins eh? That would be pretty small (I presume just a typo for 24 pin)

 

I have a solution I posted recently here: http://atariage.com/forums/topic/98341-whats-the-latest-atari-related-things-youve-bought-on-ebay/?p=4226774

 

Happy to program and send you a chip if you go the adapter route.

[Rybags]

When you put in the 800XL MMU does the 1200XL L1 and L2 LEDs and F1-F4 keys still function as normal?

 

Fairly sure the LEDs tap the PORTB outputs directly (the schematics from Jerzy Sobola have no reference to them on the PIA page) so the MMU in use should be irrelevant.

But... the OS code for the later XLs and the XEs retains the F-key code which should mean in theory that a 1200XL configured as a 130XE would allow the user to inadvertantly alter the extended banking which would be a bad thing.

Edited March 6, 2019 by Rybags

[+Nezgar]

14 pins eh? That would be pretty small (I presume just a typo for 24 pin)

 

I have a solution I posted recently here: http://atariage.com/forums/topic/98341-whats-the-latest-atari-related-things-youve-bought-on-ebay/?p=4226774

 

Happy to program and send you a chip if you go the adapter route.

 

Actually, looking at the original post of this thread, the mod described allows you to use a 2764 EPROM for BASIC directly without an adapter in a 1200XL. The adapter I referenced would be otherwise useful for any other XL or XE BASIC socket in a stock configuration. Also, the U1MB upgrade also provides BASIC, so you wouldn't need a separate BASIC ROM either, maybe someone else can clarify since I don't have a U1MB.

[Gunstar]

Since I don't have EPROM burner, where could I get a 14 pin EPROM with Basic C ?

Since Steve at Atarimax sells a 1200XL kit (for 32-in-1 OS) which includes a new MMU and an EPROM of BASIC C, I suspect he would have them. Email him, he may be willing to sell you just BASIC C eprom separately.

 

EDIT: I am assuming you meant a 28-pin eprom, which is 14-pins per side. The original socket on the 1200XL is a 24-pin socket, but the board has room for 28-pin, but some jumpers have to be moved and the MMU swapped out too. I'm not sure if you are planning on using the BASIC eprom on a 1200XL or not, just pointing this stuff out considering the thread title.

Edited March 6, 2019 by Gunstar