The LaST Upgrade Part 21 - STFM BLiTER

Last updated April 14, 2016



Later ST's had a socket space for a BLiTER (BLock Image Transfer, or BLIT) chip but was never fitted. There are a few theories as to why this was. Ranging from, the Blitter wasn't ready when the STFM went to market, or Atari were going to offer it as a upgrade later on, but never did. It was probably it wasn't ready, or Atari intentionally held back the Blitter until the STE was released. While the STE had stereo sound and a better sound system overall, it also offered a larger colour palette and the next TOS version 1.62, There wasn't any real "power" increase in the hardware. IMHO Atari held back the blitter for the STE to make it a better machine overall than the ST series. The Blitter of course giving some useful features to speed up some graphic related operations. The STE without the Blitter would seem a bit of a let down upgrade wise for those who had brought a ST, at least it would in my opinion :) If anyone knows the "real" story about the blitter in the STFM then please let me know.

What actually is the Blitter for ? The BLiTTER is just the Bit-Blt (BLiT) algorithm as specified by Newman and Sproul ("Principles of Interactive Computer Graphics", McGraw-Hill, 1979, Chapter 18). It is meant to copy graphical data, organized in bit maps, and manipulate those by applying masks, halftones and logically combine source and destination. The Atari STE BLiTTER is a slightly more advanced version of this set of algorithms since it has direct memory access and does not rely on an external bus master to feed it data. (ref.


There are still ( of sorts ) a ongoing debate on if the blitter is worth it or not. There was of course some STE games which used the blitter, but not as many as people would hope for. There are patches being done to games to make use of the blitter, which improves scrolling and other cool things. So games are slowly being adapted to make use of the blitter more.

While it appears not to have been used in a vast amount of games ( from what I have read around the Internet) people tend to forget the Blitter wasn't just for making games faster, it is also heavily used in GEM & The Desktop. Anything from windows / dialog boxes to text rendering and graphics all get a really nice speed boost! Blitting graphics almost 600% and text over 200%. Even GEM Windows reaching near 200% speeds. Defiantly a nice speed boost!



The main problem with upgrading the STFM is the lack of the Blitter chip itself and the PLCC socket. Generally new blitters can be obtained buy often at a high price along with the sockets often around $50. Secondhand/used ones are about much cheaper, but the sockets are generally old now and I wouldn't class them as reliable anymore. Generally the only source for the PLCC sockets is old motherboards. This is due to the fact Atari (also some other manufactures at the time) used a odd "offset pin" aligned PLCC socket. These offset pin sockets are next to impossible to find and if found, tend to be a high price compared to modern PLCC sockets.

As you can see on the above images, original socket (left) the pins are not aligned like they are on newer sockets (right). So Atari users (among other retro hardware) you cannot simply buy a new PLCC 68 socket and expect it to fit. This has been catching people out for many years :)



So what is the solution in 2015 ? Well I spent a little time and developed the "Funky PLCC 68 adapter".

This converts what I call the "funky PLCC 68" with is funky offset pins, to a generic (modern) PLCC 68 socket.

As can be seen the adapter is very small and fits neatly under the modern PLCC socket and solders into the motherboard. The overall height increase is typically about 2-5mm depending on how it is assembled.

These PCB adapters and new blitters are available in my STORE





To start with you need to identify the top and bottom of the PCB!

Simply check with a meter to see if you have a connection where the red line is shown on the PCB.

If you have a connection, that is the TOP of the PCB (which is where the socket will sit on top of). If you do not have a connection then your PCB is upside down. So flip it over and re-test with meter.




First of all the Funky PCB slots into the normal PLCC socket pins as shown above. What must be done next is to trim the pins so they are level with the PCB. Yes I really did just say that. Some people may break into a cold sweat at the thought of not having pins pushing beyond the PCB by a few millimeter's. Though these holes are PCB VIA's and are tin plated "though" the hole. So what we do is solder as normal, but use the solder sparingly and with a good flux content. What will happen is the solder will be sucked into the VIA's (Capillary action in fancy talk)


Above (left) the pins are expertly cut to the level of the PCB and then soldered on the above right image.

So why are we cutting these pins I hear you cry ? Well firstly, the pins will get in the way of soldering the header pins, secondly, if the pins are not cut then they may short out on the motherboard itself as often there are multiple vias under the socket. Also on the Atari STFM, there is a height limit, which unless the whole adapter is kept as short as possible, it is unlikely to fit under the metal shielding, Thirdly, I can sit laughing at you as the pins go flying across the room as you are cutting them off, watch'ya eyes! Not sure if I mentioned actually soldering the pins yet, but you should probably go do that next :) Also watch that you do not block up any of the other holes on the PCB. If you managed to block some holes up (you did didn't you ?) Then I would suggest fluxed de-soldering braid to suck up the solder, Otherwise the header pins won't fit in the holes in the next step , and we wouldn't want that would we.


I recommend using long header pins. While shorter pins can be used, it can be a bit more tricky to cut them as explained later.. The pins strips (at least the ones I have) come in strips of 16, so they are broken into 4x8 and 4x9pin strips. The 8 pin ones are placed first as shown in the image on the right. BUT, I do recommend using a second Funky adapter PCB to hold the pins while they are being soldered. Otherwise if the pins are not perfectly straight you may well have insertion problems.


No real project is without PVC bodge tape, so here is its use in the assembly. Firstly just stops the "top" PCB from dropping down while the pins are being soldered into place. Secondly, squishing the tape roll makes a useful holder to solder the pins. Dual use PVC bodge tape- awesome :o) I could have gone one better and used 2 different colours of bodge tape, but that would have involved getting up off my chair, and the floor looks a long way down from where I am sat :o)


In goes the 9 pin header pins. Simply pushed in though the top PCB and then soldered in at the bottom. I STRONGLY recommend (notice the caps and the bold text there! I could have underlined it, but I didn't want to over do it!) you double check there are no shorts on any of the pins at this point.


The spare Funky Adapter PCB is just pushed down out of the way as shown on the left most image. At some point ( I think it was yesterday) I mentioned using smaller header pins. If you use the smaller height pins, then you will have to cut the pins as close to the black plastic part as possible. Otherwise, the pins will not be long enough to solder into the motherboard. So they have to be done neat and accurately. I use the longer pins as you can pretty much hack them at any length since they will have to be cut again once soldered into the motherboard anyway.


At this point remove the "spare PCB" and you are ready to solder the socket into the motherboard. It is important to keep the socket as low as possible otherwise the metal shielding will not fit above it.

What I suggest is cut a small piece of card (cereal box is ideal as its thin) and place it under the socket PCB so it does not short out on the motherboard via's. This way the socket can be pushed down as far as possible without risking shorting on the motherboard.

Then simply solder in all the pins and trim the lengths. Then thats it all done :)

Also note on the STFM you need to unsolder the jumper links W3 & W4. Jumper links on the MEGA ST are unfortunately not labeled but there are 2 near the blitter IC.

For testing I recommend Francis Bullen's BLITTER demo which can be downloaded HERE.

This page was brougth to you by apple byte vokda and variuous varyious wariaous , lots of pro-trackery tunes (: and yes I spelt funky wrong on the PCB, but nobody noticed did they ;o)