Jump to content

Photo

Atari 800xl Missing Last 8 Bytes of RAM?


5 replies to this topic

#1 xucaen OFFLINE  

xucaen

    Stargunner

  • 1,304 posts
  • Back from the flood, looking to buy more games!
  • Location:Massachusetts

Posted Sat Aug 11, 2018 2:29 PM

I just replaced these 4 chips:
 
 
U2 IC Decoder C061428
U3 IC Mem Mngt Unit (MMul B) C061618
U4 IC (8kx8) Basic ROM RevB C060302
U5 IC (16kx8) OS ROM C061598
 
 
I had been getting red ROM bars in the memory test. Now ROM is green, RAM is green - everything looks good except the last 8 bytes of RAM are missing. Is this normal? I thought the 800xl had 48 bytes of RAM.
 
 
800xl_missing_8_bytes.jpg
 
 
If you are interested in the back story, see this thread: http://atariage.com/...t-shows-errors/


#2 flashjazzcat ONLINE  

flashjazzcat

    Quadrunner

  • 14,043 posts
  • Location:United Kingdom

Posted Sat Aug 11, 2018 2:43 PM

The BASIC ROM accounts for 8KB (kilobytes, not bytes) and the operating system is 16KB long, which added together make 24KB. 64 - 24 = 40, which is the number of RAM blocks you're seeing there.

 

Everything looks good. ;)



#3 SoundGammon OFFLINE  

SoundGammon

    Stargunner

  • 1,354 posts

Posted Sat Aug 11, 2018 4:09 PM

Turn off the power, hold down Option button, power on.

 

The screen for testing should come up, not basic. 

 

Start memory test and the last 8 blocks should show up!



#4 xucaen OFFLINE  

xucaen

    Stargunner

  • Topic Starter
  • 1,304 posts
  • Back from the flood, looking to buy more games!
  • Location:Massachusetts

Posted Mon Aug 13, 2018 7:44 PM

Turn off the power, hold down Option button, power on.

 

The screen for testing should come up, not basic. 

 

Start memory test and the last 8 blocks should show up!

 

Indeed, you are correct. I was able to see those last 8 bytes. Thanks!

Everyday I learn something new about my 800xl. :)



#5 Nezgar OFFLINE  

Nezgar

    Stargunner

  • 1,340 posts
  • Location:Regina SK Canada

Posted Mon Aug 13, 2018 9:12 PM

1 block = 1 Kilobyte (1024 bytes)

#6 xucaen OFFLINE  

xucaen

    Stargunner

  • Topic Starter
  • 1,304 posts
  • Back from the flood, looking to buy more games!
  • Location:Massachusetts

Posted Tue Aug 14, 2018 4:07 AM

1 block = 1 Kilobyte (1024 bytes)

 

Yup, I got confused. ;-)






0 user(s) are browsing this forum

0 members, 0 guests, 0 anonymous users