The plan... 2018
Posted: Fri Dec 07, 2018 11:18 am
The mongrel edition board is the planned version 2 of the remake board. Now before anyone gets excited, this is probably going to be more like towards the end of next year before this board sees the light of day.. There's a lot of work to be done yet..
The majority of the current fixes are listed in the revision G thread below..
https://www.exxosforum.co.uk/forum/viewt ... =19&t=1230
Because the GLUE & MMU are basically impossible to find, I have purchased a fairly large stock from Atari freaks of the SMT version. These will have to be soldered directly to the motherboard but as there is a shortage of these chips, is the only real option.
The mongrel edition got its name because we are actually going from a socket to a SMT chip which cannot be updated or changed in the future, at least with the socket it could open the door to the FPGA world. Though as the FPGA stuff is looking like it has a bleak future, the project is basically going on hold while the mongrel board is done. At least it will have all the updates some other things added on as well.
Things to do circuit wise is ...
To fix the reset switch footprint, I still haven't done this!
Add the video DAC circuit and remove the old RGB drivers.
Change the GLUE & MMU to the SMT versions.
1772 & DMA circuit needs a total rebuild to include current modifications.
I plan to make the next board full-sized, but I need to work at all the hole locations etc which will take a great deal of time itself.
I also plan to add internal DMA header to fit the internal ultra Satan.
There will be a DIP 68000 connector somewhere so my SEC BOOSTER can plug into this board eventually.
A lot of the decoupling capacitors will likely be changed to SMT versions.
The reset circuit needs updating to the new chip.
IDE - Assuming the project is up and working at that time.
"Super GLUE" - Possible to add in a PLD for TOS206 decoding. Be the same PLD which does the floppy GAL logic as well. MAybe even the "DoubleST" mods. Needs a lot of thinking about yet though...
LS chips replaced - A lot of the chips will be replaced with single gate "tiny logic". A lot of gates are not used in some of the LS chips. Also there is a lot of "double inversions" in the circuit which can be changed to a single buffer chip. The inverters were most likely used in that way because of the need for a open collector high-output drive current gate.. But with modern parts we can do this with a single noninverting buffer. So a lot of the chips can be removed and compacted into smaller gates. Also possible if we have a PLD on there, a few functions could be rooted through that as well.
Other possible thoughts...
Socket to add my HD V7 floppy GAL mod. This will allow 1.44 floppies, does the media change fix, and hopefully with a little recode in the same chip, drive A/B swap can be added. But that is a subproject needs to be tested out first (lack of time again for that).
Also similar I want to try and add the "Double ST" speed up. Where the MMU & RAM can be double clocked for a across the board 200% speeds. The problem with this project is that the shifter gets double clocked also, and is not very stable in mono mode. I hope the FPGA HDMI board can be adapted to fix that problem in the future.
I was of course looking towards the FPGA blitter. But of course this project is turning into a epic amount of messing about. So that project will just have to wait until I have more time for it all.
RAM..
This of course is a problem.. At the time I created the original schematics Falcon RAM boards were available very cheaply and easily obtainable. Though of course as a year passed before the board was produced, these pretty much vanish totally leaving everyone in a bit of a fix.
I was planning on adding DRAM directly onto the motherboard, but as these chips are hard to solder and hard to diagnose, they would be better being on their own board so they can be tested individually. But this basically means my MMU STFM board, why don't want people to be forced to buy this rather expensive kit. Creating a new board take a great deal of work, but it basically would end up being the Falcon RAM board again. It still is rather expensive.
I see the overall cheapest and easiest solution is to use right angle simm sockets. This way the simm and replaced towards the front of the motherboard, under the keyboard, out of the way, where there is not much height available for much else anyway.
The sockets are fortunately expensive, they seem to be £15 in RS.. But it is still half the price of my Falcon memory board. It rules out some connectors and soldering and another PCB, so likely this will be solution done.
Other thoughts..
It is likely the new motherboard will have to be done on 4 layers. This will double the price of the board unfortunately. Also as the board will be larger, assuming I do the full-size board, that is doubling the price up as well. Though I have been using JLC for some boards lately and they do not seem to bad overall. They are the cheapest for projects like this.. I do not think the price will end up being more than the original board anyway. As always import taxes and charges tend to add a large lump onto all this stuff
If I have forgotten anything, then shout out will update this post..
The majority of the current fixes are listed in the revision G thread below..
https://www.exxosforum.co.uk/forum/viewt ... =19&t=1230
Because the GLUE & MMU are basically impossible to find, I have purchased a fairly large stock from Atari freaks of the SMT version. These will have to be soldered directly to the motherboard but as there is a shortage of these chips, is the only real option.
The mongrel edition got its name because we are actually going from a socket to a SMT chip which cannot be updated or changed in the future, at least with the socket it could open the door to the FPGA world. Though as the FPGA stuff is looking like it has a bleak future, the project is basically going on hold while the mongrel board is done. At least it will have all the updates some other things added on as well.
Things to do circuit wise is ...
To fix the reset switch footprint, I still haven't done this!
Add the video DAC circuit and remove the old RGB drivers.
Change the GLUE & MMU to the SMT versions.
1772 & DMA circuit needs a total rebuild to include current modifications.
I plan to make the next board full-sized, but I need to work at all the hole locations etc which will take a great deal of time itself.
I also plan to add internal DMA header to fit the internal ultra Satan.
There will be a DIP 68000 connector somewhere so my SEC BOOSTER can plug into this board eventually.
A lot of the decoupling capacitors will likely be changed to SMT versions.
The reset circuit needs updating to the new chip.
IDE - Assuming the project is up and working at that time.
"Super GLUE" - Possible to add in a PLD for TOS206 decoding. Be the same PLD which does the floppy GAL logic as well. MAybe even the "DoubleST" mods. Needs a lot of thinking about yet though...
LS chips replaced - A lot of the chips will be replaced with single gate "tiny logic". A lot of gates are not used in some of the LS chips. Also there is a lot of "double inversions" in the circuit which can be changed to a single buffer chip. The inverters were most likely used in that way because of the need for a open collector high-output drive current gate.. But with modern parts we can do this with a single noninverting buffer. So a lot of the chips can be removed and compacted into smaller gates. Also possible if we have a PLD on there, a few functions could be rooted through that as well.
Other possible thoughts...
Socket to add my HD V7 floppy GAL mod. This will allow 1.44 floppies, does the media change fix, and hopefully with a little recode in the same chip, drive A/B swap can be added. But that is a subproject needs to be tested out first (lack of time again for that).
Also similar I want to try and add the "Double ST" speed up. Where the MMU & RAM can be double clocked for a across the board 200% speeds. The problem with this project is that the shifter gets double clocked also, and is not very stable in mono mode. I hope the FPGA HDMI board can be adapted to fix that problem in the future.
I was of course looking towards the FPGA blitter. But of course this project is turning into a epic amount of messing about. So that project will just have to wait until I have more time for it all.
RAM..
This of course is a problem.. At the time I created the original schematics Falcon RAM boards were available very cheaply and easily obtainable. Though of course as a year passed before the board was produced, these pretty much vanish totally leaving everyone in a bit of a fix.
I was planning on adding DRAM directly onto the motherboard, but as these chips are hard to solder and hard to diagnose, they would be better being on their own board so they can be tested individually. But this basically means my MMU STFM board, why don't want people to be forced to buy this rather expensive kit. Creating a new board take a great deal of work, but it basically would end up being the Falcon RAM board again. It still is rather expensive.
I see the overall cheapest and easiest solution is to use right angle simm sockets. This way the simm and replaced towards the front of the motherboard, under the keyboard, out of the way, where there is not much height available for much else anyway.
The sockets are fortunately expensive, they seem to be £15 in RS.. But it is still half the price of my Falcon memory board. It rules out some connectors and soldering and another PCB, so likely this will be solution done.
Other thoughts..
It is likely the new motherboard will have to be done on 4 layers. This will double the price of the board unfortunately. Also as the board will be larger, assuming I do the full-size board, that is doubling the price up as well. Though I have been using JLC for some boards lately and they do not seem to bad overall. They are the cheapest for projects like this.. I do not think the price will end up being more than the original board anyway. As always import taxes and charges tend to add a large lump onto all this stuff
If I have forgotten anything, then shout out will update this post..