Ram 256K Memory Problem - 1200XL

[oracle_jedi]

I need some expert help diagnosing a problem with a Rambo XL memory card in a 1200XL.

 

The Atari boots fine and runs most everything without any problem, including the Ramdisk, T34 and most 128K games I have tried.

 

Commando (256K) does not work, the game starts but then the display corrupts with garbage.

 

I ran the XRAM021 program from Satantronic, and it lists 15 banks of memory for a total of 240K - a bank at $87 (10000111) is not listed.

 

Additionally, the bank at $83, when tested, reports an error, and the machine usually locks up at that point.

 

I checked the solder connections and they all look ok, could this be a bad ram chip? Any ideas where to start?

 

The base 64K seems ok, the self-test completes without error.

 

 

A few additional specs: 1200XL with 256K Rambo, 800XL ROM chip and a PAL ANTIC.

 

Any help appreciated, thanks!

 

Graham

[+bob1200xl]

If it is a RAM chip, it will be bit-specific - one bit will fail at all addresses or, since self-test runs, a range of addresses. The fact that $87 is not listed points you at the best place to start. Use a ASM/ED cart and try storing data into $83 and then $87. You should see a picked or dropped data bit. Do you know how XRAM021 tests memory? The failure will probably be limited to a small range of addresses which, hopefully, you can hit. Once you know the bit that's failing, change the IC that stores that bit.

 

What king of error does it report?

 

Bob

 

 

I need some expert help diagnosing a problem with a Rambo XL memory card in a 1200XL.

 

The Atari boots fine and runs most everything without any problem, including the Ramdisk, T34 and most 128K games I have tried.

 

Commando (256K) does not work, the game starts but then the display corrupts with garbage.

 

I ran the XRAM021 program from Satantronic, and it lists 15 banks of memory for a total of 240K - a bank at $87 (10000111) is not listed.

 

Additionally, the bank at $83, when tested, reports an error, and the machine usually locks up at that point.

 

I checked the solder connections and they all look ok, could this be a bad ram chip? Any ideas where to start?

 

The base 64K seems ok, the self-test completes without error.

 

 

A few additional specs: 1200XL with 256K Rambo, 800XL ROM chip and a PAL ANTIC.

 

Any help appreciated, thanks!

 

Graham

[+warerat]

Your machine might be OK. The file version of Commando needs 320K (extended 256K + 64K main). The 256K Rambo is only 192K extended + 64K main.

[_Fandal_]

I need some expert help diagnosing a problem with a Rambo XL memory card in a 1200XL.

 

The Atari boots fine and runs most everything without any problem, including the Ramdisk, T34 and most 128K games I have tried.

 

Commando (256K) does not work, the game starts but then the display corrupts with garbage.

 

I ran the XRAM021 program from Satantronic, and it lists 15 banks of memory for a total of 240K - a bank at $87 (10000111) is not listed.

 

Additionally, the bank at $83, when tested, reports an error, and the machine usually locks up at that point.

 

I checked the solder connections and they all look ok, could this be a bad ram chip? Any ideas where to start?

 

The base 64K seems ok, the self-test completes without error.

 

 

A few additional specs: 1200XL with 256K Rambo, 800XL ROM chip and a PAL ANTIC.

 

Any help appreciated, thanks!

 

Graham

 

Have you read this topic? I would guess you have 192kB of expanded memory...

 

F.

[MEtalGuy66]

Based on everything you said, it sounds like your RAMBO XL is working fine.

 

I think I had problems running that 256k Commando .XEX on my 320K XE as well.. Cant remember what I did to fix it.. I think I had to run it from MyDOS or DOS 2.5, rather than SpartaDOS..

[oracle_jedi]

If it is a RAM chip, it will be bit-specific - one bit will fail at all addresses or, since self-test runs, a range of addresses. The fact that $87 is not listed points you at the best place to start. Use a ASM/ED cart and try storing data into $83 and then $87. You should see a picked or dropped data bit. Do you know how XRAM021 tests memory? The failure will probably be limited to a small range of addresses which, hopefully, you can hit. Once you know the bit that's failing, change the IC that stores that bit.

 

What king of error does it report?

 

Bob

 

 

I need some expert help diagnosing a problem with a Rambo XL memory card in a 1200XL.

 

The Atari boots fine and runs most everything without any problem, including the Ramdisk, T34 and most 128K games I have tried.

 

Commando (256K) does not work, the game starts but then the display corrupts with garbage.

 

I ran the XRAM021 program from Satantronic, and it lists 15 banks of memory for a total of 240K - a bank at $87 (10000111) is not listed.

 

Additionally, the bank at $83, when tested, reports an error, and the machine usually locks up at that point.

 

I checked the solder connections and they all look ok, could this be a bad ram chip? Any ideas where to start?

 

The base 64K seems ok, the self-test completes without error.

 

 

A few additional specs: 1200XL with 256K Rambo, 800XL ROM chip and a PAL ANTIC.

 

Any help appreciated, thanks!

 

Graham

 

 

It just reports "ERROR!" and locks up.

[oracle_jedi]

I need some expert help diagnosing a problem with a Rambo XL memory card in a 1200XL.

 

The Atari boots fine and runs most everything without any problem, including the Ramdisk, T34 and most 128K games I have tried.

 

Commando (256K) does not work, the game starts but then the display corrupts with garbage.

 

I ran the XRAM021 program from Satantronic, and it lists 15 banks of memory for a total of 240K - a bank at $87 (10000111) is not listed.

 

Additionally, the bank at $83, when tested, reports an error, and the machine usually locks up at that point.

 

I checked the solder connections and they all look ok, could this be a bad ram chip? Any ideas where to start?

 

The base 64K seems ok, the self-test completes without error.

 

 

A few additional specs: 1200XL with 256K Rambo, 800XL ROM chip and a PAL ANTIC.

 

Any help appreciated, thanks!

 

Graham

 

Have you read this topic? I would guess you have 192kB of expanded memory...

 

F.

 

 

Thanks Fandal!

 

So it would seem that the XRAM021 tool reporting 15 banks of memory with a Rambo XL is normal, and so it is reporting an error with bank $83 - thank you to remowilliams for that info.

 

I downloaded and have the Commando 192K version running now.

 

Thanks to everyone who responded.

 

Graham

[ClausB]

Here's an explanation of the 256K XL banking method:

 

In 1984 I designed the 256K "Quarter-Meg" XL RAM upgrade published in BYTE for September, 1985. It used 8 banks of 32K each. In 1985, after the 128K XE came out, I redesigned the upgrade for 16 banks of 16K. Later, that design was sold as the "Rambo XL".

 

The XL and XE computers use Port B bits to control memory configuration. Bits 7, 1, and 0 control ROM/RAM switching. In the XE, bit 4 enables extended RAM for the CPU and bit 5 enables it for ANTIC, and bits 3 and 2 select one of four 16K banks.

 

In the upgrade, bit 4 enables banked RAM for the CPU and ANTIC. Banked RAM appears in place of normal RAM at addresses $4000-$7FFF. Bits 6, 5, 3, and 2 select one of sixteen 16K banks. Four of those banks mirror the normal 64K XL RAM, and four others mimic the extended XE RAM, as below.

 

PB  Bank  RAM
--  ----  ---
$FF none  normal
$83   0   mirror of normal $0000-$3FFF (page 0, stack, OS variables, DOS, etc. -- dangerous bank selection)
$87   1   mirror of normal $4000-$7FFF (same address as bank area -- useless bank selection)
$8B   2   mirror of normal $8000-$BFFF (usually screen RAM -- not very useful bank selection)
$8F   3   mirror of normal $C000-$FFFF (RAM under OS ROM -- useful)
$A3   4   extended
$A7   5   extended
$AB   6   extended
$AF   7   extended
$C3   8   extended
$C7   9   extended
$CB  10   extended
$CF  11   extended
$E3  12   XE-compatible extended
$E7  13   XE-compatible extended
$EB  14   XE-compatible extended
$EF  15   XE-compatible extended

Now you can see why the RAM utility program does not recognize $87 because it's the same as normal RAM. You can also see why it crashes with $83 because it probably clobbers the OS, DOS, or even itself when it tries to write into that bank.

[cephallus]

Great explanation, thanks for posting that!