phantom bus accelerator & clock patch

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exxos
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Re: phantom bus accelerator & clock patch

Post by exxos » Mon Feb 25, 2019 11:38 am

tuxie wrote:
Mon Feb 25, 2019 11:35 am
Just some thoughts, i think you give the SDMA more time to take over the Data. I tested it alot and also instable falcons are working better with this patch. Feel free to try it out! Its just how i do it, you can do what you want ;)
I do not have any bus accelerators so I cannot try it, hence why I started this thread.
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Re: phantom bus accelerator & clock patch

Post by tuxie » Mon Feb 25, 2019 11:39 am

Did also repaired non accelerated falcon with this patch... somaybe give it a try :)

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Re: phantom bus accelerator & clock patch

Post by ctirad » Mon Feb 25, 2019 12:00 pm

exxos wrote:
Sun Feb 24, 2019 9:35 pm
Cool! Maybe you can clear up the slow buffer used for the sdma clock ?
The original clock patch design (a single "slow" SN7404N with separated SDMA feed, terminated by 150pF capacitor) was not invented by me, actually. It was a 1:1 copy of the clockpatch of BSS Nemesis accelerator. I decided to use this circuit because it was the only one proven to solve all SDMA issues at any BUS speed. And it still is.

However, with later batches of the SN7404N i bought for the further production, some people reported a stability issues, especially in Cubase audio. In short, the new clockpatch chips (same type, same manufacturer) was the cause. I confirmed it by retrofitting one of the chips into my old Nemesised Falcon, that started to have the same stability issues immediately.

So i decided to design a new version of the clock patch, where the good old SN7404N (or equivalent) is used for the SDMA buffer only and the CPU/FPU/Expansion buffering is done by additional 74F04. This clock patch is recomended for any Falcon, CT6x(e) or even unaccelerated as the ultimate solution.

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Re: phantom bus accelerator & clock patch

Post by exxos » Mon Feb 25, 2019 12:05 pm

ctirad wrote:
Mon Feb 25, 2019 12:00 pm
So i decided to design a new version of the clock patch, where the good old SN7404N (or equivalent) is used for the SDMA buffer only and the CPU/FPU/Expansion buffering is done by additional 74F04. This clock patch is recomended for any Falcon, CT6x(e) or even unaccelerated as the ultimate solution.
That is something I don't understand either, the 74XX series maxes out around 12MHz I think. So overclocking that chip to 25MHz would basically mean huge voltage drop in its output.. Which also seems to fit with why some clock patches use a voltage divider to drop the voltage..

Maybe you could try my idea as it is simple on your machine ?
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Re: phantom bus accelerator & clock patch

Post by tuxie » Mon Feb 25, 2019 12:40 pm

The Volage isnt the problem, the Problem is the Timing , a F type 74F04 has 4ns per gate. Instead 20ns or so with LS or 7404. And when you put it through 2 gates then you have 20ns.

Its more an timing issue instead of Voltage!!

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Re: phantom bus accelerator & clock patch

Post by exxos » Mon Feb 25, 2019 12:56 pm

tuxie wrote:
Mon Feb 25, 2019 12:40 pm
The Volage isnt the problem, the Problem is the Timing , a F type 74F04 has 4ns per gate. Instead 20ns or so with LS or 7404. And when you put it through 2 gates then you have 20ns.

Its more an timing issue instead of Voltage!!
Well, I want to see proof of this. Fact is, some patches use voltage dividers to reduce the voltage, which reduces ringing. Adding huge delay can also have same effect. Slow gates have slow rise and falls times higher the frequency. which again, reduces the voltage. Slower gates also cannot react to ringing so it solves it that that. So you cannot simply make the assumption that the delay is the cure.
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Re: phantom bus accelerator & clock patch

Post by tuxie » Mon Feb 25, 2019 1:07 pm

I Say it from my experience site, did repair and boosted a lot of falcons. !!! So what should i say ?

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Re: phantom bus accelerator & clock patch

Post by ctirad » Mon Feb 25, 2019 2:50 pm

exxos wrote:
Mon Feb 25, 2019 12:05 pm
That is something I don't understand either, the 74XX series maxes out around 12MHz I think.
The SN7404N is rated up to 35MHz. The "F" is good maybe up to couple of hundreds of MHz.
Maybe you could try my idea as it is simple on your machine ?
I cannot. Mainly because I no more own a Falcon :(
Anyway, about 20 years ago I did a lot of tests that involved various 74xx types (LS/HC/HCT/F, even the socialistic "Tesla" MHB ones) and circuits including different kinds of termination. I didn't found anything, that would work at least the same as the discussed one.

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Re: phantom bus accelerator & clock patch

Post by Steve » Mon Feb 25, 2019 7:56 pm

Just some photos of the clock patch I made myself from the Phantom schematic, I *know* it isn't the prettiest but I was proud of myself :)

Schematic:
phan.png
phan.png (51.45 KiB) Viewed 324 times
Backside of my pcb:
IMG_20180510_182317.jpg
IMG_20180510_182317.jpg (380.45 KiB) Viewed 324 times
Front side of pcb:
IMG_20180511_134149.jpg
IMG_20180511_134149.jpg (405.82 KiB) Viewed 324 times
Connection to DSP line:
IMG_20180511_134410.jpg
IMG_20180511_134410.jpg (370.94 KiB) Viewed 324 times
Connection to SDMA line with capacitor to ground:
IMG_20180511_134446.jpg
IMG_20180511_134446.jpg (318.1 KiB) Viewed 324 times
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Re: phantom bus accelerator & clock patch

Post by exxos » Mon Feb 25, 2019 7:58 pm

Cool.

I actually found the capacitor made things worse.

Looks like the second chip does a inversion.. 40ns delay at 25mhz.. but with the delays of the chip, its probably more like a buffer..
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

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