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SIMM Boards & Memory

Atari Notes By Vic Lennard
Published April 1995

Need to upgrade your ST's memory? Vic Lennard looks to RAM the point home...

Why has the ST sold something like a million units in the UK? Why, some 10 years after its appearance, is the ST still one of the best value‑for‑money home computers? Apart from its innovative design (for a computer of 1985 origin, anyway), the ST is robust and generally cheap to repair and upgrade. For instance, a replacement internal floppy drive costs less than £40; one of the powered versions for a Mac will set you back almost four times this figure.

Back in 1985, it was inconceivable that any computer program would require more than 1Mb of RAM, but this has changed. Most of the major sequencing packages need 2Mb if you intend to access all of the features, and software that incorporates sample playback, such as Software Technology's Breakthru, will happily use a full 4Mb, if available.

Last month, I looked at the various options you have if you're looking to replace your Atari with a completely new ST, MegaSTe or Falcon.However, there's every chance that there's nothing wrong with any current machine you have that a memory upgrade wouldn't sort out. So, let's look at the available upgrade options...

Older And Bolder

If you own an old STF or STFM, you may well only have 0.5Mb of memory. After all, this is fine for running a sequencer such as Concerto. There are two ways to upgrade: easy or hard! Yes, you could strip your machine down and solder 16 RAM chips and 16 capacitors into the blank part of the memory board to bring your machine up to 1Mb, but this has two drawbacks. Firstly, there is no way to further upgrade without adding another circuit board. Secondly, do you really want the hassle of soldering that little lot and finding that your work of art is pretty to look at, but little else (ie. it doesn't work...)?

The best option is to fit a SIMM board. SIMMs (Single In‑line Memory Modules) are the industry‑standard memory boards used in most computers, and they simply clip into a slot — no soldering required.

The only problem with fitting a SIMM board in an ST is lack of space. Ever since I fitted a 2Mb upgrade to my STF some years ago (a large, chip‑based board that was supposed to sit behind the keyboard), the front of the casing has continued to bow. This is partly due to the size of the board, and partly due to the extra heat generated with the upgrade fitted.

Nevertheless, there is a space between the power supply and the floppy disk drive, and most upgrades utilise this.

DIY Time...

Could you carry out the upgrade yourself? If you have a fear of anything technical, then possibly not. Otherwise, the job is generally quite straightforward. Flip your ST over and you'll see seven screws in square holes. Once these are removed, the top plastic cover can be taken off by lifting from the left, and manoeuvring the case around the floppy drive button. To the left is the power supply, covered with a metal shield, while the floppy drive is to the right, probably covered with a smaller metal shield. Both shields have to be removed, followed by the floppy drive (another three screws on the rear) and the power supply (two screws on the top). Finally, the all‑in‑one metal shield for the ST has to be removed by releasing the numerous metal twists and removing various screws. Result: a naked ST (ooh‑er...).

Most upgrades have two small boards — one which has to be plugged on top of the Memory Management Unit (MMU) chip, and another which goes into the Video Shifter socket, normally hidden away in a silver box at the centre of the main board. Both of these can cause problems. Sometimes, the socket in which the MMU sits is such that a great deal of force has to be exerted on the square 'plug‑over' board — far more than you probably feel happy with! Additionally, the MMU or Video Shifter chips may be surface‑mounted — in other words, soldered. In the case of the MMU, a clip‑on socket can be provided for a square chip, but a rectangular chip will need expert attention, as will a soldered‑in Video Shifter.

The STE‑Asy Option...

Once the SIMM board has been installed in an STF or STFM, you're in the same position as an STe owner. A SIMM board has four slots, each of which can accept a single SIMM of 0.25Mb or 1Mb capacity.

A little understanding of the ST's memory configuration is needed at this point. Essentially, an ST has two banks of RAM; a 1Mb machine has half a meg of memory allocated to each bank, for example. Of the four SIMM slots, two are assigned to the 'top' bank and two to the 'lower' bank. Both banks must have the same amount of RAM — you can't use a single 1Mb SIMM to get 1Mb of memory. For this, you would have to use four 0.25Mb SIMMs (for further possible memory configurations, see the box elsewhere on this page).

So how does an STe owner upgrade from 1Mb? To get to the SIMM slots, you only need to remove the seven screws as detailed above, remove the top cover and the shield over the power supply . With 1Mb of total RAM, you'll find that all four slots are inhabited by 0.25Mb SIMMs. An upgrade to 2Mb requires two 1Mb SIMMs. However, your existing four 0.25Mb SIMMs needn't be thrown away — you can use two of these along with the two 1Mb SIMMs to get a 2.5Mb configuration, but you will need a 'patch' — a small AUTO folder program that accesses the extra 0.5Mb.

Does the extra half meg make much difference? It certainly can if you're running something like Cubase Score v.2.0 with all of the modules and a detailed score. That half meg can be the difference between finishing your work and getting an 'out of memory' message. And it's effectively free; most ST upgrade suppliers will provide you with the 2.5Mb patch free of charge, as the program itself is either PD or shareware.

Mega Time

The Mega ST is identical to a standard STFM, except that it has the distinct advantage of space. Fitting a SIMM board is very easy, especially as the Video Shifter chip is always in a socket. Upgrading a MegaSTe is even easier. Like the STe, it already takes standard SIMMs, so a memory upgrade is simply a matter of plugging in SIMMs of the necessary value.


Some Atari computers do not lend themselves easily to upgrades. Falcons, for instance, use a memory module of 1, 4 or 14Mb. An 'upgrade' is a matter of purchasing a higher‑value module and plugging it in — and while you may be happy for a couple of 0.25Mb SIMMs to hit the bottom of the bin, you'll certainly feel the pinch with a 4Mb Falcon module! As I said last month, the trick is to buy a Falcon with a memory configuration appropriate for your needs to start with. If you intend to work with Cubase Audio or Logic Audio, save yourself a great deal of headache by investing in a 14Mb machine.

As for TTs and STaceys, these are best left to the experts. The TT is quite different from the rest of the range in the way it accesses memory, while the STacey is a pig to take apart.

In recent years, it has never ceased to amaze me how many people praise their 'new' ST after a memory upgrade. You can take almost any ST up to 4Mb for less than £100 — and use some of that extra memory to install a RAM disk, so that file saves are instantaneous...

Thanks For The Memory: ST Memory Configurations

0.52 x 0.25Mb
14 x 0.25Mb
22 x 1Mb
2.52 x 1Mb + 2 x 0.25Mb*
44 x 1Mb

* requires a small AUTO folder program.

About The Author

Vic Lennard has been an Atari enthusiast since 1987. He runs Club Cubase UK along with Ofir Gal, and is author of the MIDI Survival Guide, available from the SOS Bookshop. Rumour has it that he's about to launch a new Atari mag...