Dr. Brilliant's INCREDIBLE ATARI BRAIN TRANSPLANTS
All about 8-bit memory upgrades.
Why not an Atari 800 with 256K to 1Mb of useful internal memory? Why not a 512K XL? Or why not put your XE into six-figure RAM with a full megabyte of add-on memory?
Many experienced Atari users seem endlessly fascinated with the potential of beefing up the memory capacity of their trusty 8-bit computers - especially if they are like me and have invested hundreds (if not thousands) of dollars and hours into Atari 8-bit equipment and software.
When Antic asked me to try writing the definitive article about 8-bit Atari memory upgrades, I evaluated commercial packages and public domain schematics for every Atari model made. I covered every upgrade product I could find. As a key part of my research, I personally made hardware upgrades on two Atari XLs and three 800 models.
Upgrades are now available for every Atari computer ever made. But if you own a 400 or a 600XL you should unload it on your kids or your mother-in-law. The 400 and 600XL are harder to upgrade and less flexible because of their small size and lack of a video monitor port.
If you own an Atari 800, there are at least eight public domain upgrades and the commercial Magna Systems RAMcharger you can install. For the 800XL and 1200XL there are three professional upgrades-from Magna Systems, ICD's RAMbo XL and the Newell 256KXL.
For XEs, the only commercial upgrades I know of come from Magna Systems, but there are several in the public domain. New from Innovative Concepts is the RAMdrive + XE-GM1 (reviewed in Antic, August 1988), which converts the XE Game System into a 128K computer that is 100% compatible with the 130XE.
Sources for commercial upgrades and a tested public domain upgrade are provided at the end of this article. Prices for the commercial products are often subject to some changes because of continuous fluctuations in the prices of memory chips.
The author and Antic Magazine are not responsibile for any damages which might result when readers carry out electronic construction projects described in this article. Any original factory warranty remaining on your Atari is voided when you open the computer case.
Before starting to discuss the specific memory upgrades available, we need to introduce some information about the way that the 8-bit Atari handles memory chips.
The most commonly used type of memory chip is Dynamic Random Access Memory (DRAM). DRAM stores information as single bits in micro-miniature capacitors. Think of these chips as paper cups with holes in them-over time, the chip will lose its memory unless you keep refilling the capacitors. This process is called refreshing and is an important factor in upgrade design and implementation.
Your computer arranges memory bits in a grid of rows and columns which are "decoded" and brought out to address pins on the chips. Each standard RAM is arranged as a single row of bits like 64K X 1-or 256K X I in the quarter-megabyte RAM chips. Eight RAM chips together give a one-byte-wide line of memory-64K (or 256K) long. With a little manipulation of address decoding, you can rearrange the memory into any shape you want.
The original Atari arrangement is 64K of memory space in one block, with RAM in the first 48K and the operating system and hardware addresses in the top 16K. Newer Atari computers like the 800XL and 65XE start with a 64K block of RAM having the upper 16K available as RAM or the OS. When two banks of memory share the same address space, you can only select one at a time in a process called bank selecting. Any number of banks can occupy the same address space in RAM, but only one at a time. In the 130XE and all upgraded computers, the additional RAM is banked into the second 16K of the address space. (See Figure 1.)
Power does not come without a price, however The Atari's 6502 CPU chip has only 16 address bits to control 64K of address space. To control the additional RAM banks, more address bits are needed. When only the 800 was available, Axlon came Out with a 128K upgrade that used $CFFF (decimal 53247) as a hardware address to control the banks. Current 800 upgrades still continue this tradition.
In the older 8-bit models, the space $C000 to $CFFF was unused. But when the newer XLs put RAM there, the Axlon standard had to be dropped. It's a real shame, too, be cause with the Axlon standard you could access 16 megabytes of banked RAM!
When the 1200XL was released, Atari stole joystick ports 3 and 4 (also
called PORTB of PIA, the Peripheral Interface Adapter) and connected them
internally to control the extra memory that was banked along with BASIC,
the operating system, ROMS, hardware and various LEDs.
Atari removed these LEDs from their plans for the 800XL. This left five of the PORTB pins unused. So when the 130XE was released, Atari assigned four PORTB pins to control the additional memory Bit 4 of PORTB selects the CPU to work in the extended RAM banks, while bit 5 does the same for the ANTIC chip.
When these bits equal 1, the respective integrated circuit is restricted to the main bank. Bits 2 and 3 select one of the four 16K banks, all of which have the same address of $4000 to $7FFF (decimal 16384 to 32767). A 256K computer needs two more bits to select all the banks, but we have only one free in PORTB. All XL upgrades take bit 5 of PORTB from ANTIC to use in bank selecting, so ANTIC can't use extended RAM independently of the CPU.
The Magna Systems one-megabyte RAMcharger received an excellent review in the July 1987 Antic. The Magna Systems Axlon-compatible upgrades range from 256K to 1Mb and are super-easy to install on an Atari 800. The Magna RAMcharger is actually a self-contained plug-inboard. All you do is take out the two screws holding the top lid covering the factory RAM cards (right behind the cartridge slots). Pull out the middle RAM card and pop in the RAMcharger, making sure it doesn't touch the neighboring cards. Now screw the lid back on and the installation is finished.
I found a few quirks in the RAM-charger's address decoding. The board not only responds to the addresses in Axlon range but also to some zero-page addresses, which might make some programs incompatible. Magna can compensate for this by either defeating the bank selecting with a switch or by installing a jumper wire to the ROM board in slot 1.
If you're an Atari 800 do-it-yourselfer, you can make your own 256K
quarter-megabyte upgrade from public domain instructions. I personally
did two of these and had no problems with the David Byrd upgrade listed
with this article.
two XLs and
Some users who have built public domain upgrade projects report memory losses because of poor design in the refresh circuits. With the first upgrade I performed, I didn't notice any problems, but I was able to produce memory dropout under certain circumstances. The Byrd upgrade I list did not exhibit any dropout, but it could be that the RAM chips I used have long retention times. In any case, if you build a do-it-yourself upgrade, use the best chips you can find.
MYDOS will configure the 256K upgrades as a 2,000-sector RAMdisk and can recognize a full megabyte on the 800. These upgrades are fully Axlon-compatible and will give you an edge on any program that recognizes Axlon RAM. The problem is that few software products are doing so. For example, Springboard's Newsroom and BASIC XE from ICD/OSS only work on an XL/XE.
Nevertheless, adding Axlon RAM makes your 800 compatible with Print Shop Companion, and SynFile + will boot with 288K of free RAM. By contrast, you only get 128K on XE and XL upgrades. For this reason alone, I doubt that I'll ever get rid of my upgraded 800.
The three commercial upgrades- from Magna Systems, ICD's RAMbo XL (reviewed in the July 1986 Antic) and the Newell 256KXL-deliver high quality at a low price. I also know of one 256K public domain XL upgrade project that was being sold direct by the author. (At this writing Antic could not verify a current address for the PD author If the information later becomes available, we will print it in I/O.-ANTIC ED)
Installing an upgrade for the Atari XL requires dismantling the computer, removing the RAM chips and one decoder chip, and making attachments to several other points on the circuit board. All the XL upgrades set up the RAM as a 64K main bank with 12 16K banks in the $4000 to $7FFF window.
It is harder to upgrade a computer in which the chips are not socketed-and many 800XLs have their chips soldered in. But while desoldering the original RAM chips makes installation more time-consuming, it's still not too difficult for a person who is reasonably dextrous and has a fair amount of experience in constructing electronics projects.
You can either do it yourself or get manufacturer installation of the ICD RAMbo XL or the Newell 256KXL. But Magna Systems insists on installing all the XL/XE upgrades it sells. The price includes installation and you must send your computer to them.
Magna Systems and the public domain both offer 320K, 576K and 1088K upgrades for the Atari 130XE. So far there are no commercial programs designed to utilize this extra RAM for anything except a RAMdisk. Unless you really need a RAMdisk larger than 1,600 sectors, I see little use for this much RAM.
The 130XE's additional RAM banks need more control bits than are free in PORTB. So you lose the self-test routine (no big deal) with 576K. You lose built-in BASIC with 1088K, but you can get around this by using a cartridge-based BASIC.
With so many different types of upgrades available, there are some concerns about compatibility. I tested David Byrd's public domain 800 upgrade, RAMbo XL and the Newell 256KXL for compatibility with PaperClip, SynFile +, Print Shop and Print Shop Companion, Typesetter, Newsroom, DOS 2.5 and MyDOS 3.2B.
No matter how much memory is crammed into an Atari 800, it could still not be expected to handle the 130XE-only versions of PaperClip or Typesetter-although it could run the older versions. (There is no 800-compatible version of Newsroom.) On the plus side, an 800 has 160K more RAM with SynFile + than an XE compatible.
The XL upgrades will run all XE software, and both the RAMbo XL and the 256KXL ran every program I tested. However, RAMbo XL gives you 700 more text lines in PaperClip than Newell. While MyDOS works for all of the upgrades, it must be reconfigured for each one. MyDOS came configured for the Newell, but to reconfigure it for the other upgrades isn't easy because of the unclear manual.
There is one subtle difference between Newell and RAMbo involving the ANTIC chip. All upgrades use pin 5 of PORTB, so you cannot independently set ANTIC to the extended RAM or the main bank. This leaves only three options- place ANTIC permanently in extended bank (undesirable), place it permanently in main bank (like Newell and Magna), or tie it to the CPU so that the CPU and ANTIC are always in the same bank (like ICD's RAMbo).
With the Newell/Magna method, if you try to page-flip the screen through RAM banks, you'll be disappointed. However, you can use the entire main bank RAM space for graphics and the extended banks without fear of "seeing" data on the screen.
RAMbo lets you place multiple screens in banked RAM and flip to them. While there are theoretical advantages to both systems, it actually makes little difference because you rarely place ANTIC into the bank access window. Usually the screen RAM is in the 16K bank above the access window.
I accidentally discovered that with RAMbo you can switch all banks into the window, including the 64K of main RAM. The first bank includes DOS and your programming, the third bank contains BASIC and the last 16K is under the operating system. This can be a real boon to a BASIC programmer. You get 24K of extra RAM space for graphics or data, besides the 12 banks used by the RAMdisk.
Installation of the 800 public domain upgrade requires you to build a circuit board or "dead bug" installation of four ICs on one of the 16K memory boards, plus some modification to the ROM board. Magna Systems RAMcharger boards are simple to pop into the Atari 800, but you may need to add one extra jumper wire to the ROM board.
All of the 800's chips are plugged into sockets. So are most l200XL chips and some of the 800XL chips- but not XE chips. Do-it-yourself upgrades usually aren't recommended if the factory chips are soldered to the board, but there are solutions. RAMbo XL is comparatively the easiest to in-stall, requiring only one or two jumpers, one cable to the PIA chip, and removal of the RAM chips and one other IC.
The Newell upgrade calls for five wires to go to PIA and three jumpers elsewhere. Newell should have installed a ribbon cable like the RAMbo to make the five connections to the PIA. To make connections to the PIA, you can pry it out of the socket and bend up the pins. I attached a 5-pin piece of a 14-pin IC socket to the end of the ribbon cable to press onto the PIA instead of soldering. If it's soldered in place, you can simply solder right to the side of the pins without removing the IC. The older ANTIC can't refresh the 256K chips, so Newell requires you to replace it if it has an older part number (CO12296 instead of C021697). The Magna and lCD products don't require this.
If you use a small wattage iron (about 25 watts) and keep soldering times below five seconds, you will not damage anything. If your chips are soldered, you can either desolder them all at once-or use my secret shortcuts!
The only chips you really must remove are eight RAMs and one 16-pin IC. The rest of the connections can be "tack-soldered" to the pins on ANTIC, to the circuit board, or to wherever else is necessary.
After chips are removed, they're useless, so you can just cut them out and toss them. Cut the pins close to the plastic body with a pair of fine cutters. Now you can remove each pin individually, which is easier than 16 pins at once.
Afterward, open the circuit board holes by heating the solder pads until the solder melts. Poke the hole open with a round toothpick or embroidery needle, remove the heat, then remove your probe. When all the holes are open, insert sockets and solder from the bottom with fresh solder. When all necessary chips are removed and sockets installed, installation can proceed normally.
New chips retain their memory longer, so when you turn off the computer you must wait as long as 20 seconds to reboot, or you may get strange results. If you are in BASIC, you can POKE 580,1 then press [RESET], or type BYE and press [RESET].
The 800XL upgrades offer the widest software compatibility. If you need a large database, it might be better to upgrade an older 800 for use with SynFile +. One main reason for upgrading an Atari is so it can emulate the 130XE with software that uses the extra RAM. All upgrades mentioned here do that job, but the ICD gives you PaperClip files with 700 more lines. Expanding a 130XE gains you nothing with commercial software, but if you need a huge RAMdisk for a BBS, contact Magna Systems.
Don't try do-it-yourself memory installation if you have electrophobia. You might be able to get a member of your local users group or school electronics shop to do it for you, if you don't want to pay shipping and installation charges to have your upgrade manufacturer do the work.
The bottom line is this-bare upgrade boards cost about $40 and right
now your cost for 256K worth of chips will be around $100. Add these prices
and you come very close to the cost of a new Atari 130XE. Chip prices are
widely expected to fall within a few months, but until then a memory upgrade
only delivers a slight cost advantage over getting a new XE. But if you
want a larger RAMdisk or larger database files than a standard 130XE supports,
then an upgrade may be worth the extra time and money.
Dr. Lee Brilliant is a physician in the San Fernando Valley area of Los Angeles and a well-known Atari 8-bit programmer/author
1220 Rock Street
Rockford, IL 61101
$39.95 without RAM chips
602 East Highway 78
Wylie. TX 75098
$39.95 without RAM chips
147-05 Sanford Avenue,
Suite 4E, Flushing, NY 11355
$225 approx.-256K for 800, plug-in board includes chips $195 approx.-256K for XL, including chips and installation(Phone for other RAM prices)
PUBLIC DOMAIN 800 UPGRADE
800 Plus 256K (Rev: D, Ver. 1.6)
Ad Astra, January/February 1987 (For version with corrected PC board layout, send stamped self-addressed return envelope to: Lee Brilliant, C/O Antic Editor, 544 Second Street, San Francisco, CA 94107)