This section by Andreas Koch -- Version 3.6 from June 2008
 
A) Atari 400/800 RAMdisks:  
  
- Size:  64k XRAM (+ 32k RAM)  
  Banks: 0 thru 3  (total memory = 96k RAM)  
  Types: Axlon (=Atari) and compatibles;  
  
- Size:  128k XRAM (+ 32k RAM)  
  Banks: 0 thru 7  (total memory = 160k RAM)  
  Types: Axlon (= Atari) and compatibles;  
  
- Size:  256k XRAM (+ 32k RAM)  
  Banks: 0 thru 15  (total memory = 288k RAM)  
  Types: D. Byrd and other self-made / Axlon-compatible RDs;  
  
- Size:  512k XRAM (+ 32k RAM)  
  Banks: 0 thru 31  (total memory = 544k RAM)  
  Types: self-made / Axlon-compatible RAMdisks;  
  
- Size:  1024k XRAM (+ 32k RAM)  
  Banks: 0 thru 63  (total memory = 1056k RAM)  
  Types: self-made / Axlon-compatible RAMdisks;  
  
- Size:  2048k XRAM (+ 32k RAM)  
  Banks: 0 thru 127  (total memory = 2080k RAM)  
  Types: self-made / Axlon-compatible RAMdisks;  
  
- Size:  4096k XRAM (+32k RAM)  
  Banks: 0 thru 255  (total memory = 4128k RAM)  
  Types: self-made / Axlon-compatible RAMdisks;  
  
=> Note that all so-called Axlon "compatible" (256k-4096k) RAMdisks  
   normally do not homebank when RESET is pressed (a fix should be  
   available somewhere), whereas original Axlon RAMdisks do homebank  
   properly !!  (Special thanks to Lee Barnes for this note !!)  

Axlon supporting software includes: MyDOS, TopDOS, Synfile +,
Syncalc +, and more (I cannot test it, alas)

- Size:  64k for 48k RAM and 4 banks of 4k XRAM
  Banks: 4x 4k banks (bankswitching via $C000-CFFF)
  Types: one Mosaic 64k "RAM-Select" board

- Size:  128k for 48k RAM and 20 banks of 4k XRAM
  Banks: 20x 4k banks (bankswitching via $C000-CFFF)
  Types: two Mosaic 64k "RAM-Select" boards

- Size:  192k for 48k RAM and 36 banks of 4k XRAM
  Banks: 36x 4k banks (bankswitching via $C000-CFFF)
  Types: three Mosaic 64k "RAM-Select" boards

Mosaic supporting software includes: Mosaic`s Super Drive (a kind of
virtual DOS), Visicalc, TopDOS, and more (again, I cannot test this!)
For the XL/XE Ataris there are some translator disks, that enable this
mode (e.g. the Ultra-Translator) with 48k + 4k RAM...

B) XL/XE - 64k base RAM plus XRAM:  
  
- Size:   64k (total = 128k RAM, 4 banks)  
- Banks:  3, 7, B, F  
- Blocks: E, = 1 block * 4 banks 
- Types:  130XE RAMdisk, Turbo-Freezer-XL + 64k, self-made RAMdisks...  
  
- Size:   128k (total = 192k RAM, 8 banks)  
- Banks:  3, 7, B, F   
- Blocks: AE, = 2 blocks * 4 banks  
- Types:  Compy-Shop 600XL with 192k, Turbo-Freezer-XL + 128k,   
          self-made RAMdisks...  
  
- Size:   256k / 26AE (total = 320k RAM, 16 banks)  
- Banks:  3, 7, B, F  
- Blocks: 26AE, = 4 blocks * 4 banks  
- Types:  Compy-Shop 800XL RD., Compy-Shop 130XE RD.,   
          Peters/David Megaram 1, Peters/David Megaram 2,   
          Peters/David Megaram 3 with 256k, self-made RDs...  
  
- Size:   256k / 8ACE (total = 320k RAM, 16 banks)  
- Banks:  3, 7, B, F  
- Blocks: 8ACE, = 4 blocks * 4 banks  
- Types:  Newell, Rambo-XL, Scott Peterson, Atari Magazin,   
          TOMS, self-made RDs...  
  
- Size:   512k / 26AE (total = 576k RAM, 32 banks)  
- Banks:  1, 3, 5, 7, 9, B, D, F  
- Blocks: 26AE, = 4 blocks * 8 banks  
- Types:  none (that I know of) at the moment - but possible!  
  
- Size:   512k / 8ACE (total = 576k RAM, 32 banks)  
- Banks:  1, 3, 5, 7, 9, B, D, F  
- Blocks: 8ACE, = 4 blocks * 8 banks  
- Types:  Scott Peterson, TOMS, self-made RDs...  
  
- Size:   512k / 02468ACE (total = 576k RAM, 32 banks)  
- Banks:  3, 7, B, F
- Blocks: 02468ACE = 8 blocks * 4 banks  
- Types:  1) upgrade / combination of 26AE and 8ACE RAMdisk   
          types to 512k RAM or into *one* 02468ACE RAMdisk;   
          idea by me, built by Bernhard Pahl
          2) Upgrade of the Rambo XL to 512k by Dan Schmid   
          (see Pooldisk Too, Subdir ACE/ Acec202a.ATR and   
          Acec202b.ATR) and of course 3) self-made RAMdisks...  
          3) 512k SRAM upgrade by Bernd Herale, available  
          from mega-hz, Wolfram Fischer: www.

- Size:   1024k / 02468ACE (total = 1088k RAM, 64 banks)  
- Banks:  1, 3, 5, 7, 9, B, D, F
- Blocks: 02468ACE, = 8 blocks * 8 banks  
- Types:  Newell, Scott Peterson, TOMS, Satantronic`s 1MB-  
          PC-SIMM-RD, self-made RDs...  
  
- Size:   1024k / 26AE (total = 1088k RAM, 64 banks)  
- Banks:  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
- Blocks: 26AE, = 4 blocks * 16 banks  
- Types:  Mathy van Nisselroy`s 1024k XEGS-PC-SIMM-Upgrade!  
          (with some changes probably also usable for XL and XE,  
          see also: http://www.mathyvannisselroy.nl/) 
  
- Size:   1024k / 8ACE (total = 1088k RAM, 64 banks)  
- Banks:  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
- Blocks: 8ACE, = 4 blocks * 16 banks  
- Types:  none (that I know of) at the moment - but possible!  
  
- Size:   1024k / 0123456789ABCDEF (total = 1088k RAM, 64 banks)  
- Banks:  3, 7, B, F
- Blocks: 0123456789ABCDEF, = 16 blocks * 4 banks  
- Types:  luckily, none at the moment...  
  
- Size:   1024k / ??? (max. memory = 1088k, 64 banks)  
- Port-Bits / Control-Bits: $D301 = 2,3,6,7   
                            $D600 = 0,1 (or switches);  
- Banks:  $D301: 3, 7, B, F, $D600: ???
- Blocks: $D301: 26AE, $D600: ???
- Types:  David/Peters Megaram 3 with 1024k RAM (and the switches   
          positioned to 1 x 1024k)  
  
- Size:   2048k / 02468ACE (total = 2112k, 128 banks)  
- Banks:  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
- Blocks: 02468ACE, = 8 blocks * 16 banks  
- Types:  self-made RAMdisks...  
  
- Size:   2048k / 0123456789ABCDEF (total = 2112k, 128 banks)  
- Banks:  1, 3, 5, 7, 9, B, D, F
- Blocks: 0123456789ABCDEF, = 16 blocks * 8 banks  
- Types:  self-made RAMdisks...  
  
- Size:   4096k / 0123456789ABCDEF (total = 4160k, 256 banks)  
- Banks:  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
- Blocks: 0123456789ABCDEF, = 16 blocks * 16 banks  
- Types:  Newell, FTE, self-made RAMdisks...  
  
Well, I will not go into details with the disadvantages and possible   
software-problems with RAMdisks beyond 512k RAM (possible problems
might be the unavailability of the Self Test, XL/XE Basic, RAM under the 
OS, separate Antic access, etc. depending on the type of RD/XRAM)...
  
C) XL/XE - XRAM minus 64k Base-RAM:  
  
- Size:   192k / 8AE (total = 256k RAM, usable = 12 banks)  
- Banks:  3, 7, B, F   
- Blocks: 8AE, = 3 blocks * 4 banks  
- Types:  older Newell RAMdisks (replace 64k by 256k);  
  
- Size:   192k / ACE (total = 256k RAM, usable = 12 banks)  
- Banks:  3, 7, B, F   
- Blocks: ACE, = 3 blocks * 4 banks  
- Types:  newer Newell RDs, newer Buchholz-RDs, Rambo-XL,   
          self-made RAMdisks (replace 64k by 256k)...  
  
- Size:   448k / 2468ACE (total = 512k, usable = 28 banks)  
- Banks:  3, 7, B, F
- Blocks: 2468ACE, = 7 blocks * 4 banks  
- Types:  self-made RDs (replace 64k by 512k)...  
  
- Size:   896k? / 0248ACE (total = 1024k, usable = 56 banks)  
- Banks:  1, 3, 5, 7, 9, B, D, F
- Blocks: 0248ACE = 7 blocks * 8 banks  
- Types:  Bob Woolley`s 1200XL 1MB Upgrade, self-made RDs   
          (replace 64k by 1024k)...  
  
Although these RAM upgrades are relatively easy to build  
(and to install into the computer), they make problems with  
quite some software. Some programs tend to use the base RAM  
as extra RAM / RAMdisk with these upgrades, which will most  
often result in a crash of the computer. Next, most extra RAM   
testers will show more extra RAM (or a bigger RAMdisk) than   
there is really available (e.g. with a 256k upgrade you will  
see 240k extra RAM, but there is only 64k base RAM + 192k  
extra RAM). Alas, this is a typical hardware problem for these  
upgrades and it cannot be solved or avoided with software...  
  
D) XL/XE: Parallel-Bus-Devices:  
(600XL/800XL = Parallel Bus, XE = Cart.-Port + ECI)  
  
- Size:   64k / E (total = 128k RAM, 4 banks)  
- Banks:  3, 7, B, F  
- Blocks: E, = 1 block * 4 banks
- Types: Turbo-Freezer-XL by Bernhard Engl with 64k XRAM 
 
- Size:   128k / AE (total = 192k RAM, 8 banks)  
- Banks:  3, 7, B, F  
- Blocks: AE, = 2 blocks * 4 banks
- Types:  Turbo-Freezer-XL by Bernhard Engl with 128k XRAM  
  
- Size:   256k / 9ABE (total = 320k RAM, 16 banks)  
- Banks:  3, 7, B, F  
- Blocks: 9ABE, = 4 blocks * 4 banks  
- Types:  Turbo-Freezer-XL by Bernhard Engl with 256k XRAM  
  
- Size:   256k / ??? (total = 320k RAM, 16 banks)  
- Banks:  unknown !!  
- Blocks: unknown !!
- Types:  Yorky-XL by Richard Gore / Derek Fern (from   
          GB/UK) with 256k XRAM  
  
- Size:   256k / ??? (total = 320k RAM, 16 banks)  
- Banks:  unknown !!  
- Blocks: unknown !!
- Types:  Multi-Input-Output-Hard disk-Interface (MIO) with 256k   
          XRAM by ICD and its re-release by MetalGuy  
  
- Size:   1024k / ??? (total = 1088k RAM, 64 banks)  
- Banks:  unknown !!  
- Blocks: unknown !!
- Types:  Multi-Input-Output-Hard disk-Interface (MIO) with 1024k   
          XRAM by ICD and its re-release by MetalGuy  
  
E) XL/XE: RAM/Flash-ROM/... Cartridges:  
  
- Rambox II with 256k RAM by JRC (Czech Republic; with special   
  RAMdisk drivers for TT-DOS and Bewe-DOS!)  
- Ramcart 64k by LK Avalon (Poland) 
- Ramcart 128k by LK Avalon (Poland; binaries of the EPROM and GAL 
  chips of this cart can be found on ABBUC magazine 64) 
- Ramcart 256k by Zenon/Dial (Poland) 
- Ramcart 512k by Zenon/Dial (Poland) 
- Ramcart 1024k by Zenon/Dial (Poland) 
  (for some hints and pics see: www2.asw.cz/~kubecj/acarts.htm)  
- Flash-ROM cart 128k / 1Mbit "Atarimax" by Stephen Tucker  
  (although they are not usable as extra RAM / RAMdisk at the moment,  
  I am quite sure that it is possible to write some drivers and thus  
  use the Atarimax Flash-ROM carts as extremely fast floppy drives!)  
- Flash-ROM cart 1024k / 8Mbit "Atarimax" by Stephen Tucker  
  (for information and complete documentation plus software see:  
  www.atarimax.com/flashcart/documentation/index.html )  
- and many others I do not know and I do not have any info about;  
  
Even cartridges can be used as RAMdisks (= fast floppy drives),  
especially RAM-carts or Flash-RAM carts. But they function like  
most other Super- or Mega-Carts, meaning the bank-switching  
techniques are also used there. Since the subject carts and  
bank-switching carts is quite enormous, I will not discuss it or  
present any information here. Just try to find a large description  
by John K. Picken ("RAM/ROM Control on an XL/XE") if interested in that  
subject (e.g. at Jindrich Kubec`s homepage: www2.asw.cz/kubecj/... ).  
  
Finally thanks and credits for this subject and lots of (used /   
borrowed) information therefore go to: Lee Barnes, Russ Gilbert,   
Mathy van Nisselroy, Erhard Puetz, Mathias Reichl, Ron Hamilton,   
Wes Newell, Guy Ferrante, XI of Satantronic, Bernhard Pahl, Walter  
Lojek and Voy/Dial. Also thanks to John K. Picken who wrote an  
excellent article about A8 extra RAM / RAMdisks and A8 cartridges and  
their technique of bank-switching. I know this list has still some
errors and is missing some information, alas, without your help I am 
unable to correct the errors or to fill in the missing information... 
Andreas Koch