Axlon RAMDisk

128K Memory System for Atari

A while ago a group of employees left Atari and formed Axlon Co. to manufacture add-on products for the Atari computer. They produce a 32K RAMCram card, and a 256K RAM system, complete with expansion interface.

So when ads began to appear for their RAMDisk, I was intrigued. I couldn't resist calling them for more details.

They turned out to be most friendly and mailed me a loaner RAMDisk for evaluation. This review is based on my use of the product for a month.

The RAMDisk arrives in a 9" x 11" x 1" blue box which contains a manual, a diskette, and a memory cartridge. The manual is housed in an attractive notebook with the diskette in a side pocket.

The memory board looks like an Atari 16K cartridge except that it has no top or sides. (It does have front and back covers, though.) This is probably to help the RAM Disk get rid of heat.

The manual is well written, and very, very clear. I decided to trust it immediately, and began following the setup directions.

Getting Started

First, one boots up the system with a normal Atari 2.OS DOS disk. The Axlon disk is fast formatted and uses Atari directory formats and such, but does not contain DOS.SYS or DUP.SYS, so you can't boot up with it. Next, I ran a Basic program called CREATE to create a boot disk (a disk used whenever the system is powered up or re-booted). Following the instructions, I put in the Axlon disk, then a blank disk, and created a boot disk. No problem--very easy to do.

Next, I turned the computer off, removed my middle 16K board, and put in the RAMDisk. Two memory boards are required, for some reason, on either side of the RAMDisk. Perhaps they keep it from getting the electrical equivalent of lonely,

Then, I booted up using the new boot disk. A most foreboding message flashed onscreen for about five seconds, just long enough for a speed reader to comprehend it. It pointed out that the Axlon MMS (Memory Management System) was an end-user initiated change to Atari DOS and that Axlon doesn't condone making copies and distributing them.

Here is my first complaint with the MMS, Axlon's DOS 2.OS: you have to sit through this silly legal message every time you boot up with the MMS disk. The first time, it's fun, and even witty. The second time, half witty, and after that, not funny at all. I was ready to disassemble the boot file and "short out" the message after a month of seeing it.

Once you're through the message, you get to Basic or whatever you're running. The RAMDisk hardware operates just like a normal 16K cartridge unless you specifically tell it not to. There's just about the same amount of free memory as before. So I typed DOS.

Next surprise. No click, whirr of the disk. The DOS menu popped up right away, just like the old DOS 1, but apparently without the memory sacrifice, according to FRE(0). And my, how the DOS menu has changed.

The Menu

First, the top line is not Atari 2.OS anymore. It is the Axlon RAMDisk MMS System V1.0. Most of the options look the same, but two are disabled: writing DOS files and creating MEM.SAV.

Second complaint. I don't care about MEM.SAV; I never use it. But I want to be able to write the DOS files after formatting a disk. The DOS and DUP files are on nearly every disk I have, making for few bootup problems. But Axlon doesn't want complaints about folks copying DOS, so they disabled it. Aside from these two changes the menu is a duplicate of the Atari 2.OS menu.

How do you use the RAMDisk? The RAMDisk contains 128K bytes of memory. A diskette contains around 90K. So the Axlon MMS makes "disk #4" the RAMDisk memory area. You literally use the 90K of the memory board as disk number 4.

You can copy to it, open files on it, close them, NOTE/POINT them, and so forth.

You can copy an entire disk to RAM. You can run directories, lock files--everything you can do to a normal disk--to the RAMDisk (disk 4). In short, the RAMDisk replaces disk 4.

Here's an example. Let's say I have one disk drive and I need to duplicate a disk. I load the Axlon MMS, go to DOS, and J (duplicate disk) from 1 to 4. This copies the whole diskette into RAM. Next, I put in my destination disk, and copy from 4 to 1. All done. (No more swapping diskettes back and forth.) This is very nice and very easy. It is also fast. I could load 220-sector binary files in less than a second from the RAMDisk. This compares to more than 30 seconds for a disk drive.

Software houses should take note here. The RAMDisk is a very good thing for you. Let's say you need to make 100 copies of a given diskette. Without the RAMDisk, you can either use two drives--one to read the master and one to write the destination disk (wearing the master and its drive out)--or use one drive and swap disks like mad. With the RAMDisk, you copy the master into RAM, then proceed to make your copies from RAM. This product would well pay for itself in saved time and disk drive wear--heavy use is hard on Atari drives. (By the way, I found that DOS and DUP did copy if I used the DUP DISK option; you just can't create them originally).

From Basic Assembler, and so forth, the RAMDisk is just disk 4. SAVE or LOAD; the operations run very fast. Anyone with a program that is running slowly due to disk I/O should look into the RAMDisk. A speedup factor of 20 would be easily achieved, and that's conservative. In addition, you needn't put up with disk errors and the like.

How It Works

By now you're probably curious how this thing works, so here's what I found (in the manual, all clearly laid out). In the Atari, the address space from 4000 to 7FFF is normally the second 16K board installed in the machine. The RAMDisk allows 4000-7FFF to be any of eight individual 16K boards, one at a time. Due to many arcane hardware considerations you can't access all 128K at once, only a 16K chunk of it. But which 16K is instantly selectable. This is called "bank selection."

For example, Axlon apparently puts their MMS DOS Menu on one of the 16K banks. Then, to switch to DOS, they just select that particular 16K, and run (that's why DOS comes up so fast). But also note that DOS does not take up normal 16K programming space this way; the contents of the 16K you were working in before you typed DOS are on another of the 16K boards, ready for use as soon as it is reselected. (The MMS handles the swapping back and forth to use the 90K disk area).

If you're confused, just imagine you have a pile of eight 16K memory boards and you could plug or unplug them at will into the middle slot. This is how the Axlon board works.

Physically it uses Motorola 64K x 1 chips. The raw cost of the chips on the board I calculated to be around $250, so the price of the board is quite reasonable. The construction of the board is very high quality.


Extremely high speed animation is possible using bank selection. You don't have to use the Axlon board as a RAMDisk. You can select which 16K you want directly. So several images (display lists and memories) can be stored, and switching between them determines which image is being displayed. Some impressive effects could be obtained (only) this way. Alas, I didn't have time to do much of this.

One thing I did use the system for was holding temporary files during developmental work. By having the RAMDisk hold various versions of a Basic program I was developing (with SAVE), I greatly speeded up the development time. However, there is a problem with this: turning the Atari off causes the contents of the board to be lost. And I have locked up the Atari past RESET working many, many times.

The diskette that comes with the RAMDisk also has several options to check the board out and fiddle with MEM.SAV. It even has a complete copy of the manual (over 300 sectors) as files.


And now I come to the parts I don't like about the RAMDisk.

I have already mentioned a few points, but my main problem with this unit is that it is a limited function device. It is like a plotter; some people can use it, others can't. Software houses and people with heavily disk-bound programs could make great use of this product. People who need incredible animation memory also could. But I can't for the life of me think of another use for it. It was a nice convenience when copying disks, but it just wasn't that great a help. It would take a volume operation for it to make a difference. For your average Atari user, another disk unit, which costs the same (or even a bit less) is probably a better buy. You can just do more with it.

Technical Aides

The bank selection is done in the C000 area, currently unused by Atari. My Atari sources tell me this will change in a year or so, as the operating system acquires more capabilities. The Axlon people will have to modify their board at that time.

Sector copying programs do not work with this board.

Microsoft Basic has real problems with this board. I tried the whole month to get them to work together and couldn't. As the new Basic is just plain wonderful and everyone will be buying it, the Axlon people had better get some new software out fast.

The board throws only minimal RF interference, and if you run your Atari without the top cover on for heat dissipation, you will notice minor wavy lines on your TV.

Axlon plans a RAMDisk for Apple II and Apple II Plus computers in the near future.


This is a solidly built, well documented product. It has several very useful applications. People who can use it in those applications will be most pleased with it. But those who want high speed disk I/O or temporary storage will not find it of much use. It certainly expands the capabilities of the Atari, but you may not need your capabilities expanded in that direction. Consider it as you would a piece of other special purpose peripheral equipment, such as a digitizer or modem. Will you use it? If so, it is a good product.

RAMDisk, Axlon Co., 170 N. Wolfe Rd., Sunnyvale, CA 94086. $699.

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