At the most recent VCFMW, I picked up an 800 XL. On startup, I get a very brief red screen flash followed by black when using composite to an old CRT TV. I found Shoestrings ram and basic rom diagnostic ROM and burned it to a 27C128, like he recommends. "This program installs in the OS ROM socket and is used as a means for testing the DRAM and the Atari Basic ROM. If you have some spare 27C128s lying around then this can easily be installed without an adapter in any Atari 8 bit."
When I opened the case, I have only one choice on where to install a 28 pin 27C128. Unfortunately he says to install it in place of the OS ROM. Looking at the board, the two roms that are installed are in U4 and U5. The 27C128 is a 28 pin IC, but according to the following information from the field service manual the 24 pin U4 should be where I plug the diagnostic rom into.
"U4 IC (16K X 8) OS ROM C06159S
U5 IC (8K X 8 ROM) Rev B C060302
O.S. ROM - The 800XL operating system is resident in one 16K X 8 ROM. The ROM address inputs are from CPU address lines AO through A13. The chip selects from the address decoding circuitry and generates data on CPU data lines DO through D7. The ROM requires a power input of +5 volts.
BASIC ROM - The Atari 800XL has built-in Atari BASIC (Rev. B) residing in an 8K X 8 ROM.This is equivalent to having an Atari BASIC cartridge permanently plugged into the console. Any cartridge plugged into the computer, takes precedence over the built-in BASIC."
Has anyone ever successfully used Shoestring's ram tester? Does it go in place of the Basic rom instead of the system rom? Before I spend the time desoldering chips, I need a little help.
I would ask this question on the AtariAge forum, but I'm still waiting for my status to be upgraded from guest.
When I opened the case, I have only one choice on where to install a 28 pin 27C128. Unfortunately he says to install it in place of the OS ROM. Looking at the board, the two roms that are installed are in U4 and U5. The 27C128 is a 28 pin IC, but according to the following information from the field service manual the 24 pin U4 should be where I plug the diagnostic rom into.
"U4 IC (16K X 8) OS ROM C06159S
U5 IC (8K X 8 ROM) Rev B C060302
O.S. ROM - The 800XL operating system is resident in one 16K X 8 ROM. The ROM address inputs are from CPU address lines AO through A13. The chip selects from the address decoding circuitry and generates data on CPU data lines DO through D7. The ROM requires a power input of +5 volts.
BASIC ROM - The Atari 800XL has built-in Atari BASIC (Rev. B) residing in an 8K X 8 ROM.This is equivalent to having an Atari BASIC cartridge permanently plugged into the console. Any cartridge plugged into the computer, takes precedence over the built-in BASIC."
Has anyone ever successfully used Shoestring's ram tester? Does it go in place of the Basic rom instead of the system rom? Before I spend the time desoldering chips, I need a little help.
I would ask this question on the AtariAge forum, but I'm still waiting for my status to be upgraded from guest.