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 » Sun Sep 30, 2018 11:52 pm

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 175 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 » Mon Oct 01, 2018 12:58 am

I guess the gal is out of pins to avoid using the 7474 ?
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

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

Post by troed » Mon Oct 01, 2018 10:02 am

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 » Mon Oct 01, 2018 11:32 am

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...
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

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