Boosting STFM: 16MHz bus, 64MHz Shifter

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troed
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

Post by troed »

So I'm still working the two different tracks here. The original doubleST with a stock Shifter, and a variant using the FPGA-Shifter.

For the former, I'm close to ordering a few boards. My own testboard is soon falling apart from all the modifications it's gone through.
Screen Shot 2018-10-01 at 00.43.09.png
Screen Shot 2018-10-01 at 00.43.09.png (103.17 KiB) Viewed 5400 times
(no, not final layout)

As you can see the plan is to delay /DTACK for the bus accelerated modes, using a flip-flop. Exxos was right that that was the reason behind why I often had "stuck boots".
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

Post by exxos »

I guess the gal is out of pins to avoid using the 7474 ?
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

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exxos wrote: Mon Oct 01, 2018 12:58 am I guess the gal is out of pins to avoid using the 7474 ?
I don't know at the moment if I can latch incoming DTACK to an 8MHz (GLUE clock) DTACK_OUT with the GAL. It's more about what I don't know about GAL programming yet - but it's indeed on my todo to see if I can :) Basically a GAL is really bad at counting up a delay without using up all I/O pins.

I had to move from 16V8/20V8 to the 22V10 just to get enough outputs. The FPGA version additionally needs one more.
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

Post by exxos »

troed wrote: Mon Oct 01, 2018 10:02 am I don't know at the moment if I can latch incoming DTACK to an 8MHz (GLUE clock) DTACK_OUT with the GAL. It's more about what I don't know about GAL programming yet - but it's indeed on my todo to see if I can :) Basically a GAL is really bad at counting up a delay without using up all I/O pins.

I had to move from 16V8/20V8 to the 22V10 just to get enough outputs. The FPGA version additionally needs one more.
Might be worth moving to a larger Atmel PLD like I have been using ? Then you can run flipflops for the delays, and run 2 outputs to DTACK, one delayed and one not, and just have a select line to select which dtack line to use.. I had to do that with my SEC booster as I needed to delay DTACK on higher speeds, but not delay on 8MHz stuff.

You could use the .OE function on the 22V10.. but likely would run out of IO's setting it all up.. With the larger Atmel stuff, you can use internal pin nodes, so don't need to use actual IO pins for everything...
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

Post by troed »

I've understood that there's been some real progress on the FPGA Shifter reset issues lately, while I've been much too occupied with my day job to spend time on this. I don't really have more time, but I'm really really eager to get back on track with this so I'll try to make some :)

My test machine is in a sorry state at the moment, with the DTACK delay through the 7474 not being "perfect", if I recall. I'll clean that up and possible order those test boards so that I can spend time on the software rather than hardware issues.
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

Post by exxos »

If I ever get chance, I want to do this mod on the Alpha... Also with a future board, there will be a expansion board for the GLUE & MMU where I hope to integrate the GAL onto that board.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

Post by arf »

troed wrote: Sun Mar 24, 2019 3:01 pm I've understood that there's been some real progress on the FPGA Shifter reset issues lately, while I've been much too occupied with my day job to spend time on this. I don't really have more time, but I'm really really eager to get back on track with this so I'll try to make some :)

My test machine is in a sorry state at the moment, with the DTACK delay through the 7474 not being "perfect", if I recall. I'll clean that up and possible order those test boards so that I can spend time on the software rather than hardware issues.
Is this cool project dormant?

I tried to find a “wrap-up” post/blog entry/wiki page somewhere, but weren’t terribly successful, so I guess this lengthy thread is the single source of truth?
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troed
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

Post by troed »

arf wrote: Sun Sep 25, 2022 9:54 pm Is this cool project dormant?

I tried to find a “wrap-up” post/blog entry/wiki page somewhere, but weren’t terribly successful, so I guess this lengthy thread is the single source of truth?
It is, and it is ;) While I had this mod working really well on a 1040 STFM, when I tried moving it to the H4 board I ran into clock issues. I see no reason for why it wouldn't work if I sat down with it, unfortunately, I think the early failure meant that the nicely broken out clock jumpers on the H4 were then removed from the H5.

I also don't think anybody tried replicating it. I have several small boards meant to be placed on the H4 clock pins made if there's serious interest in adding to the effort.

/Troed
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Re: Boosting STFM: 16MHz bus, 64MHz Shifter

Post by exxos »

Just for clarification for this. While I did this mod as well way back in July 19, 2016 And later did it on the alpha motherboard with the intention of doing it "properly" on the H4. The problem is because of the wakeup states of various chips on the motherboard you had a 1 in 4 chance of it basically booting up at all. And a 1 in 2 chance of the video not been screwed up.

If your chips generally favoured starting up in the same state then the problem is not so noticeable. However it could work most of the time, or not work most of the time depending where wakeup states were. The workaround was to delay DTACK so it would always start up correctly but then you would lose a chunk out of the speed because of this. I did start to design workaround boards and various other ways of fixing some problems but ultimately decided it was a dead-end road because even after going through all that trouble, you could not improve things any further anyway.

So the decision was made not to bother with such mods on the H5. The clock jumpers and such were all removed. Instead we are working on the FPGA cores and just fixing problems properly right from the start. With a stable chipset we can easily have a 16Mhz bus. But the thing is things can always be improved with that method. We can add features and even try for 32Mhz bus and higher speeds. IMHO this was a more worthwhile and future proof course of action rather than trying to do the original 16Mhz hack.

For example the MMU core https://exxosforum.co.uk/forum/viewtopi ... 811#p81811 and the HDMI shifter core https://exxosforum.co.uk/forum/viewtopi ... 945#p71945 etc

Unfortunately there is unlikely ever to be any sort of solution which will be reliable across all machines. Even stock machines are just riddled with faults to start with even before looking at acceleration. It is why I abandoned the original machines and the H4 / H5 was developed. Indeed developing "hacks" on the H5 is not really what the project is aimed for. We want do to do things properly and have something which is reliable for a more production environment.

Anyway did not mean to hijack this thread. I am merely stating this project is not so simple as some may think. It is possible and when it works, it works really well. But the implications when clocks shifting phase to each other is not so simple to fix.

Indeed if someone wants to spend enormous amounts of time in getting it all working properly then of course go for it. I have no objections really if people want to try and do this on a H4 / H5. But it will never be any sort of official upgrade for the platform. The FPGA cores are the future. We can build them properly from the ground up to do what we want. There are no "hacks" involved.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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