- The LaST Upgrade -


exxos 2008 - last updated March 6, 2023


The latest batch of ROM adapter PCB's see the move from DIP ROM's to a single PLCC ROM 55ns. If you have purchased the kit which needs assembly then read the suggested install / build steps below.

Keen eyes will spot a "damaged" hole under the PLCC socket. This is done deliberately to remove a manufacturing defect which appeared on some boards. Nonetheless, it is normal and nothing to worry about :) Some assembled boards may have a wirelink to also correct a PCB defect.

Firstly I would suggest soldering on the SMT capacitor. Soldering it later can be tricky if the PLCC socket is in place first.

Next solder in the PLCC socket and the 3 header pins. Make sure you use the square header pins, not the round header pins otherwise the jumper link will not make good contact.

Note the socket has a small arrow which should be pointing towards the SMT capacitor. Make 100% sure you get the socket in the right way!

The round header pins as shown above have to be soldered the right way around. The bottom pins are thinner and longer and those insert motherboard end. The larger shorter pins solder into the ROM PCB.

There are normally 2 strips of pins supplied, you will need to cut them down to size. I would suggest not breaking them by hand or with pliers. I would suggest using a sharp knife to cut the strips to size.

At this point, assuming your old ROM's are in sockets, I would suggest using those sockets as a template to aligning the pins up correctly on the PCB. If you try and solder the pins by hand with nothing to hold them in place, you can assume to have fitting problems later on. If your motherboard does not have sockets, then use the motherboard PCB to align the pins for you.

Try and push down a little on the PCB while soldering to make sure the pins are flat against the PCB.


Next carefully push in the ROM. The "dot" on the edge of the ROM is pin 1 and should be pointing towards the SMT capacitor.


At this point I would suggest testing the board out. Place on the blue jumper link. This is the TOS select jumper. You can place a toggle switch there is you so desire.

While the board can be left plugged into the motherboard sockets, it will probably not fit under the metal shielding. I would suggest soldering the ROM PCB directly into the ST motherboard once verified working.


Jumper link to the left sets TOS104. Jumper link to the right sets TOS102. Job done :)



Assembly is similar to the STFM board above only this MEGA adapter is a different shape. Please take not as to the direction of the ROM socket, Where pin 1 is pointing towards the small SMT capacitor.


STE TOS 1.06/1.62 to TOS 2.06 UPGRADE

One of the easier and semi-popular STE upgrades is upgrading the TOS to 2.06. TOS2.06 is the last TOS version for ST/STE computers which include various bug fixes, 1.44 MB disk support (you still need a floppy upgrade kit to use 1.44 floppy's) , memory test. Adds GTP program support (GEM-Takes-Parameters). Greatly enhanced GEM GUI. IDE hard disk booting. Atari logo display at boot-up. Automatic cold boot memory test. Supports higher resolutions.

(Note you cannot upgrade STFM TOS this way, it requires a lot of hacks to get TOS206 working on the STFM)

So far I have seen 2 types of jumper links. First one is where there are 3 resistor looking links, and another type where there are 2 resistor looking links. These are printed as W102, W103, W104, where W103 may be a resistor looking like, or linked on the PCB itself as shown on the image on the right. Depending what TOS you have installed, the links may also be in different combinations or different sized ROM IC.


To fit TOS206 you simply remove the old ROM's IC's then change the jumper links as shown below. Note that these ROM's I sell in my STORE and this guide may not work with other ROM's sold around the Internet.

Note that W103 is wired on the PCB itself on my motherboard, so there is no need for a wire link for me. If your PCB is not linked, then you need to link them, a small link of wire is perfectly acceptable, you do not have to use the resistor looking links.


That's it done! Now if all goes well , you should see the Atari logo come up :) TOS2.06 is a lot "nicer" to use on the STE. Though please note upgrading TOS can break some software, but fixes are being done for popular games to be compatible.


STE TOS 1.62 / 2.06 SWITCHER

The PCB above is the new STE DUAL FAST TOS switcher board. This can be used by itself to give TOS1.62 & TOS2.06 TOS versions which are selectable by a simple jumper link or toggle switch.

The boards is "FAST TOS" capable of running at 32mhz with the addition of a 32mhz STE booster board.

Assembling is very easy and straight forward. Solder in the header strips, PLCC socket, capacitor, jumper SEL connector and you are pretty much ready to go. Pay attention to the direction of the IC and socket by the "Dot" on the IC should be near the SMT capacitor. The socket generally has a "dot" or arrow also.

The board is designed with the original OTP ROMs (smaller) than the EPROMS which are sometimes fitted later. Eitherway, if you modified the 'W' jumpers then you may need to swap them back. On my board W103 is linked on the PCB (middle and right pads). W104 & W102 are also linked middle and right pads.

Once all soldered in, you can place the board in the STE ROM sockets, though it needs pushing down as far as it will go. There is practically zero clearance between the bottom of the floppy drive and the metal shielding. I would recommend removing the STE ROM sockets and soldering the PCB in directly into the motherboard.

NOTE - While I "soldered bobbled" them over I found it wasn't connecting very well. So always use a actual wire link to save possible headaches later.

NOTE - If use use a jumper link to select TOS versions, you will need to solder the 3 header pins in, then pull off the plastic spacer to reduce the overall height of the pins. Then place in the jumper link and trim the tops off the pins If you do not do that then the pins will likely short out on the bottom of the floppy drive.

NOTE - The black wire shown is not a part of general fitting, it is part of the CPU booster and will be documented on the booster pages. So at this point you can ignore the black wire.





These black DualTOS boards will start to appear this year. These are slightly smaller than the previous blue board.

The only real change is the TOS select jumpers have gone from 3 pins to 2 pins. Also now there is a pull up resistor. So when the jumper is "missing" it will default to the upper TOS bank in the ROM. Connecting the 2 pads will select the lower bank of the ROM.

Not that SEL doesn't have to connect to the PCB, it can connect anywhere to GND on the motherboard. This way only 1 wire to the TOS board has to be routed to a switch. Of course a second wire to the switch needs to be connected to GND, but it can be soldered anywhere on the GND track on the motherboard, so this wire can be kept short and saves having a second wire going across the motherboard. Overall instead of routing 3 wires to a switch from the TOS board, only SEL is now needed.

CE is marked properly on this board. This is the pin which connects to the STE booster (if fitted). Be warned, a slight f*ck up on layers, the CE pin is marked in tin plating (should have been top silk screen sorry!) So only solder to the CE pin NOT shorting on the tin plating areas around it as this is actually wires to GND. So check with a meter after soldering a wire to the pin, that it is not shorting to the tin plated areas around the pin.




Some older machines have 6 chip TOS installed. Generally I would recommend using one of my TOS adapters and upgrading to TOS104. However on some machines it is not always possible.

As there are 2 basic versions of TOS location , here is a conversion. The left numbers are taken with TOS under the PSU. The last numbers are TOS located on the left of the motherboard. Also see images below.

U4 = HI 0 - U63
U7 = LO 0- U67
U3 = HI 1- U59
U6 = LO 1- U62
U2 = HI 2- U48
U5 = LO 2- U53



On later motherboards where the TOS ROM's are in a row as shown on the image above on the left, these motherboards can be converted to 2 chip TOS. Generally 6 chip was was V1.00 and later versions of TOS were generally 2 chip with TOS1.04. There are many combinations of TOS and 2 or 6 chip, but that is a general rule to keep things simple at this point.

I would recommend TOS1.04 be installed in all STFM machines. While other TOS versions can be made to work, it is not a simple ROM chip change as for example, TOS2.06 needs some address decoding as its ROM address is different than TOS1.04. Also generally I would advise against upgrading TOS higher than TOS1.04 if you want to keep compatibility with games and older software in general.

In anycase, here is how to convert 6 chip to 2 chip.. (note I took images of 2 differnet motherboards to show what needs to be done to save time on myself actually doing the mod)

On 6 chip motherboards there are 3 solder jumper pads to change as highlighted. 6 chip has 256K jumpers linked. Also U68 may or may not be missing. If U68 is missing, then you will need to obtain a 74LS11 IC and fit it. Do not use any other variation of this chip other than the LS version as I have found stability issues on other types such as "F" or "HCT" etc.


Notice the location of where the 2 chip ROM's are installed. Also notice the HI and LO printed on the motherboard. The jumper pads are changed to 1M. That is basically it!

I would recommend if you upgrade to TOS1.04, that you install one of my Fast-Rom adapters as shown elsewhere on this page. As if you decide to do a CPU upgrade, fast-roms will be needed. I also sell original slow ROM's in my store HERE.



Thanks to kohli79 for the image!



With 6 chip TOS impossible to find in recent years, more so TOS1.04, A new solution was needed. The new TOS kits are likely compatible with all ST/F/M machines and as a added bonus they can be used in conjunction with the V1.5 booster for faster ROM access speeds.

The problem with early ST's such as the STM and some STF & even STFM machines, is they have no option to upgrade to 2 chip TOS. Some later STFM's for example, had a additional LS IC which allowed the conversion from 6 chip to 2 chip by changing the solder pads from 256K to 1MB. Such a method is mentioned else on this page. However, some STFM machine have the LS chip missing, where it can be fitted to allow 2 chip conversion. However, earlier machines simply were never intended to be upgraded to 2 chip TOS and thus unless you can find TOS1.04 in 6 chip format you are basically out of luck. Generally 6 chip TOS is either TOS1.00 or TOS1.02. There are 6 chip TOS1.04 sets, but I have rarely seen them. So now enters my new TOS adapter kit.


Above is a example ROM layout in a STF machine. Here 6 chip ROMs are in place. I have numbered them as shown in the image and below..

HI2 - HI1 - HI0
LO2 - LO1 - LO0

The ROM kit can be inserted in any LO & HI socket. There are some wires which also need fitting. These are the GLUE's ROM select lines. These have to have to be decoded much the same way as the STFM does with 2 chip TOS. But more on that in a moment..


Some example layouts are below..


The HI board can be placed in any HI socket. The LO board can be placed in any socket. The only other change is the location of the 2 orange wires. These go in pin 20 in the ROM sockets.


One thing which may confuse, is the HI and LO ROM select lines are actually wired together. So U5 pin 20 is the same signal as U2 pin 22 etc.

Probably the easiest way is to treat the ROM board with the small IC as the master board. Place that in a HI slot. Then which ever 2 slots are left, the orange wires connect to pin 20 of the 2 remaining sockets.

There are 2 more wires to connect, these have to connect to the CPU as there are 2 missing address lines on 6 chip TOS sockets. In the above images there are a yellow and blue wire going off the bottom of the image, these 2 wires connect to the CPU as shown below..


Yellow wire is on pin 44, and blue wire is on pin 45. These feed the missing address lines to the new ROM boards.

That is all there is to it!

One thing to note , is because the new ROM boards are higher than the original roms, the PSU will likely not sit down fully. So once the new ROM boards are tested and working, you must solder them directly into the motherboard.



Version 3 of the 6 chip to 2 chip TOS104 conversation kit.

These boards have a better layout for install and testing than previous designs above, though basically the same kit. I supply the boards built and tested with exception to the bottom board which will not have the 4 wires soldered to it. The reason for this is that with so many motherboard layouts, the length of the wires needed simply varies to much, so there cannot be a "one size fits all" type of thing. So the user will need to determine the best length of wire to fit their motherboard.

These boards are intended to replace 6 chip TOS to 2 CHIP TOS where ordinarily 2 CHIP TOS would be impossible to fit (mostly STM machines). Early STF machines also had 6 chip TOS but could also be updated with a little work. Later STF boards was a little easier. Much later STFM boards I sell another kit like THIS ONE which would be better suited for revisions which have the layout for that particular design as there are no wires to solder.

Please note this kit does not fit under the PSU , so while you can follow these install steps for initial testing, you will have to unsolder 2 sockets from the motherboard and solder the ROM PCB's direct to the motherboard.

You can if you wish solder all the wires to the PCB direct without using the connectors which may save some bad connection type headaches in the future.

Install steps below...


Work out where you are going to place the 2 ROM boards. The "master" board is the one marked "HI" and also has the tiny SMT soldered on the PCB (the LO version does not have this IC).

You can actually use any of the sockets as long as the HI board is in one of the TOP sockets, and the LO board is in one of the BOTTOM sockets. Though for this guide I use the sockets on the right as shown.


First push the 2 pin connector into the top header pins as shown above. Work out a short route from the top to bottom ROM board and cut and solder the red and black wire as shown above.


On the long header on top of the HI board solder the red and green wires to the CPU as shown above.

Orange wire goes to CPU pin 45, Green wire to CPU pin 44.

NOTE: The wires may not be long enough to reach so may need extending. I may supply a small length of wire loose in the kit but the colour will be random.


Next solder the yellow and black wire has shown above. Yellow wire is 3rd hole from the left, and the black wire is on the far right hole (The colour layout is actually the same as the connector, but you only solder yellow and black)


Lastly I soldered the red and white wire from the long top connector to the U5 and U6 sockets as shown above. Ideally the sockets should be removed and wires soldered direct to the motherboard.

Place something like a piece of card over the ROM boards and connect back up the PSU and you should get this in the desktop info menu... (assuming you not ballsed up something :)

Once you are up and running. You will need to remove the 2 ROM sockets you have plugged the boards into and solder the ROM boards direct into the motherboard. Then the PSU will fit in place as normal.






Fits CO70789 style boards. TOS102 & TOS104 with 2 chip installed.. NOTE not all versions of this board have the UBE chip installed (depends on what version is purchased from my store)

This UBE version Allows changing of TOS version by holding down the reset button (for 5 seconds) while turning on the machine.

CE SELECT jumper pads select GLUE or BOOSTER decoding. By default GLUE should be selected.

BK1 & BK2 Is "bank select" to manually select TOS102 or TOS104.

RESET Pad goes to pin 18 of the CPU when the UBE switch is to be used

TS Pad is to be linked when UBE switch is used and the BK1 / BK2 jumper MUST be removed otherwise you will blow the UBE chip up!

NOTE: The image above shows MANUAL configuration for when UBE is not used, or not fitted.



NOTE: Jumper placed on the top of the GLUE chip is optional :)



Fits CO70789 style boards with 2 chip TOS installed.

CE SELECT jumper pads select GLUE or BOOSTER decoding. By default GLUE should be selected.

BK1 & BK2 Is "bank select" to manually select TOS version.

NOTE TOS206 requires a suitable decoder board such as THIS ONE.

If you have previously installed six chip TOS then you need to do the STF/M 6 CHIP TO 2 CHIP CONVERSION



A small resistor of generally 1/8watt of a typical value of 1K,2.2K,4.7k,10K etc to be placed as shown above. This resolves a problem when using the external/AUX CE pad.



One of the most annoying things about fitting the DUALTOS board is it is very close or even touching the metal shielding.generally the socket should be removed but even so there still may be not enough clearance. It would be better if the dual tos board could be moved upwards. So let's do just that!


De-solder the left and middle pad and solder the middle and right pad as highlighted within the yellow circle.

Next solder a small wire between the two points as highlighted within the red circles. Pin 8 is on the 74LS11 IC.

NOTE - Not all motherboards will have the LS11 fitted. In particular if you have had previously 6chip tos installed. Some boards may not even have a space to solder one in. Indeed the location of this chip greatly varies depending on your motherboard revision. The chip is available HERE if needed.



STE DUALTOS 1.62 & 206 WITH UBE SWITCH - NOTE not all versions of this board have the UBE chip installed (depends on what version is purchased from my store)

This UBE version Allows changing of TOS version by holding down the reset button (for 5 seconds) while turning on the machine.

RESET (blue circle) Connects the RESET line to UBE.

TS Linked to enable UBE (the jumper link on the rop right is to be disconnecte when TS is soldered)

JUMPER LINK (top right orange circle) TOS select. Open is one TOS version, linked is another TOS version.

CE only used for with STE booster.



(This board has been superceeded by the PLCC design)

If you have purchased a TOS set and a STFM TOS PCB then follow these instructions for fitting.

Below you will need these types of round header pins.

It is useful to have a old IC socket to had to hold the pins straight and in place while you solder them. If you do not do this then you will probably have fitting problems later on.

The shorter larger side of pins solder into the PCB. If you get this backwards then you may have to trim the tops off the pins in order to seat the TOS ROMs.

Make sure you get the header pins in the right places! When 100% then solder them in as show above.

Then solder the SMT capacitors as shown below.

WARNING - Now pay attention that I soldered some sockets in here as I plan to use this as a test board for testing TOS ROMS. In your case, you will solder the TOS ROM directly into the PCB (without sockets) Otherwise the metal shielding will probably not fit over the board due to height restrictions.

The ROMs may not fit perfectly level due to the some soldered pins being under the ROM chips. You could file down the pins a tiny bit if you really really really REALLY wanted too... but in general its not needed.

You next need to remove the 2 IC sockets U67 and U63. If you do not remove these then you will have height problems when fitting the metal shielding.

NOTE - If you had the 6 chip TOS fitted before then you will need to solder in a 74LS11 IC (U68) As this IC may be missing from your motherboard. You will also need to change the 3 solder blobs from 256K to the 1M location as shown in the image below.

If you need a HI-RES image then click HERE or click the image below.

Next just solder in the ROM PCB into the motherboard, make 100% sure your soldering is clean and nothing shorting out before you power up!


That is pretty much it! You should be able to verify you have Rainbow TOS by booting to GEM and clicking in the DESK menu.

TOS ROM's and adapter PCBs are available in my STORE.

ROM HACKING UPGRADES - Obsolete in 2015 - see my STORE for better upgrades

Above is a Regular STFM. TOS 1.02, 512K MB, 720K floppy.

First I am going to upgrade the TOS to RAINBOW TOS 104. I upgrade the TOS using regular EPROM which have been programmed with the TOS 104 images already.

It is noted that the EPROM's are 1MBit and are slightly longer than the TOS ROMS's. The original TOS ROM's were OTP (one time programmable) and have less pins than EPROM's. Some wiring is needed to adapt them for ST use.

I use regular turn pin sockets for this upgrade. I find it makes things nice and neat. However, if you decide to use the sockets rather than doing all the wiring directly to the EPROM, then the ST metal shield will not seat correctly as the addition of the socket makes them too high to fit. So a small hole would have to be cut in the metal shield. There are many options though this socket example is the one which I shall go with in this series.


First we must bend up and outwards the pin on the left of the IC. looking from the bottom, we count 8 pins up from the bottom left upwards. Notice the "tab" of both the socket and the IC are at the top of the image. If you get this part wrong you will wire your EPROM upside down!

Trim the bend lag back if needed. Also when you solder the bottom right pin try to only solder to the upper part of the pin and not allow the solder to run down the leg else it will not fit into the socket!


Above we now have a top view of the finished wire.


And the side view of the bent pin


and the side view of the other connection. Notice the solder is only at the top of the leg as mentioned earlier!


Now to start on the socket!


Notice the IC tab is to the left of the image. We need to cut off level the 2 end pins. Do not cut them off totally as we need to solder some wires to them. This overhang the sockets on the motherboard and if not cut , could short out onto the PCB.


Top 3 pins on the left are soldered together and linked to the top right pin only.

Then counting 8 pins up from the bottom left we link to the second pin down from the top right.


Done! Slot the EPROM's into the sockets and that's it!

The EPROM on the left I took the wire directly over the EPROM as the black wire on the right is a little harder to see.


Side view of the 2 finished EPROM's


Now they are slotted into the motherboard. Notice the overhang the IC sockets by 2 pins!

As mentioned before, the EPROM on the bottom of the picture is physically higher than the ST's metal shield so some slight metal editing is needed, or you could always removed the socket on the motherboard and solder out new sockets in place. Or just do all the wiring directly to the EPROM though I find overall the outlined method to be the neatest way, other than some small metal editing!


For those who want to solder the EPROM directly it follows much the same as the socket method. however where the plane bare wire and black wire meet, they much not touch, this can be tricky in pushing the wire into the IC socket on the motherboard.

top 3 pins get soldered as before to the top right pin. Then the second pin down from the top on the right has a loose connection th eother end where the EPROM pin was bent up.


Notice the black wire (EPROM BENT PIN UP) is not touching the bare wire.


We now have a nice RAINBOW TOS 104 installed and working :-)

I like rainbow tos as the FUJI is all different colours like a rainbow! and its even animated too!



All TOS ROM's and adapter kits are available though my webstore.