1. Not old. Vintage. :)

Antonia 4MB Upgrade

Quick quide for the Antonia 4MB upgrade for the Atari 8-bit home computer

{Recovered Atari Sector...}
________ ________

Just acquired my 3rd 4mb board (secondhand this time) in a bid to upgrade my "project - everything socketed 800xl"

here's some background of my understanding of how you can access 4mb of ram on an 8-bit atari:

Ram exceeding 48 KB on 8-bit Ataris is based around bank-switching.
A 6502 has 16 address lines. The CPU can address 64 KB total, including ram ringfenced for OS+BASIC

■ bit 0 enables or disables the OS freeing up 14 KB of RAM
■ bit 1 enables or disables the BASIC ROM freeing up 8 KB of RAM
■ bits 2 and 3 provide bank selection on 130XEs
■ bits 4 and 5 control CPU/ANTIC access (the CPU and ANTIC can bank-switch independently, which makes sense since ANTIC has its own RAM ports)allowing independent bank switching of both and allowing access to ANTIC Ram ports
■ bit 6 enables or disables XES Missile Command ROM
■ bit 7 enables or disables self-test ROM, from 0x5000 to 0x57FF; freeing up 2 KB of RAM

Most Ram expansions utilize bank-switching chips and additional memory chips, accessing more bits for bank selection.
Using 256x 16k banks (8 selection bits) - 4 MB is the maximum possible.
One or two recent expansions have a 65816 16-bit CPU, which will function in 6502 compatibility, but accesses 24 lines of address and a whopping 16mb of ram.

The main use for most ram expansions is as a ram disk, as the vast majority of software - with 130xe-specific software and demos being the main beneficiaries.

■ W65C816 CPU (standard 1.77/1.79 MHz clock)
■ 4MB configurable RAM
■ 512kB Flash ROM - 8 slots for paired OS+BASIC
■ 7-bit non-volatile configuration register
■ socketed MB means a solder-free installation

■ 600XL - 800XL - 1200XL
■ 800XE - 130XE
■ 65XE (need to ensure clearance by raising PCB with extra socket(s)
■ 65XE - 65XEN (if 130XE board)

far too simple really,
■ remove CPU
■ remove U18 [600xl only]
■ remove MMU
■ insert Antonio board
■ connect Antonio ribbon cable to MMU socket

Memory Configurations
■ 64k RAM: zero banked, enabled 4 MB of linear memory
■ 128k RAM (130XE) 64k banked, option to enable 3 MB linear memory
■ 192k RAM (192XT) 128k banked, option to enable 3 MB linear memory
■ 256k RAM (TOMS 260XE) 192k banked, option to enable 3 MB linear memory
■ 320k RAM (Rambo XL) 256k banked, option to enable 3 MB linear memory
■ 576k RAM (Compy Shop) 512k banked, option to enable 3 MB linear memory
■ 1088k RAM (Rambo XL) 1024k banked, option to enable 3 MB linear memory
■ Axlon 2 MB: 2032k - 127x16k banked, 2 MB linear memory
■ Axlon 4 MB: 4016k - 251x16k banked, zero linear memory.

Flashing the Board - this is for adding your own OS/Basic Combinations
■ Create an ATR with SDX or MyDos to contain ANT.EXE
■ add to ATR OS BASIC rom files as required.
■ ANT will display current settings (dashes indicate indicate active pairs( You MUST always use pairs) expanded memory config is displayed inverse). (
■ Board is shipped with same default XL/XE OS/Rev C Basic - in ALL slots
■ to assign a new OS/BASIC pair to a slot press "F"
■ all slot-pairs will be displayed as #0 - #7 (active slot will display # as inverse video)
■ Use cursor arrow keys to highlight slot to amend.
■ Press "L" program now confirms that you wish to Load an "O" (OS) or "B" (BASIC).
■ after making your selection program will display files on D1:
■ move cursos keys to highlight chosen file and hit RETURN. - at this stage is has NOT yet been flashed
■ Press RETURN to return to previous screen - this allows you to make other selections/changes.
■ once you have everything you want pre-loaded press "F" to flash
■ you can abort at any time (except during flashing) by pressing ESC
■ once done, press ESC - computer will reboot

Important Note:
Image below from 800XL - showing 3x ICs that are removed from 600XL only.
U18 SHOULD NOT be removed for 800xl, 1200XL or XE range


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