CT60(e) + bus acceleration

[mikro]

Is there anyone who is actually using the "native" bus acceleration provided by the CT6[03e] ? So far I've seen / used only 'external' solutions like the Nemesis/Phantom, i.e. both clock patch and bus acceleration are bundled together and the CT basically doesn't know about it.

However since the first CT60 you could install a "Czuba patch" (totally different clock patch, leaving the R2xx resistors intact and patching only one SDMA clock trace) and optionally accelerate bus from CT60 signals.

CT60e seems to only imply that possibility is still here plus people report success with exxos' clock patch so I've been wondering whether there are still people who would favour 25 MHz data bus? From what I remember, the difference was amazing, esp. without the SuperVidel, because the bus is choked with data from the CT60, plus the faster DSP of course.

[stormy]

I would 100% want a faster bus. If someone posts a tutorial it would be great!

[jvas]

I have the DSP with its own crystal, accelerated all the time (was not stable if it got the clock from the CT60, but that's my motherboard, not the CT60).
And yes, the speed boost is very good without SV. Since SV, I don't use the speed boost. Watch your SCSI reliability if you want experimenting with the boost! (mine had problems at some 060 clock speed)

[stormy]

I have the DSP with its own crystal, accelerated all the time (was not stable if it got the clock from the CT60, but that's my motherboard, not the CT60).
And yes, the speed boost is very good without SV. Since SV, I don't use the speed boost. Watch your SCSI reliability if you want experimenting with the boost! (mine had problems at some 060 clock speed)

I would like to do this mod: http://joska.duckdns.org/dsp/ as well but I find the instructions to unclear. Is there any chance you could clarify this in more detail since you have performed the mod? Thx

Specifically I find the 'piggybacking' part unclear, I can understand the soldering to the capacitor though.

[paul92706]

I have the DSP with its own crystal, accelerated all the time (was not stable if it got the clock from the CT60, but that's my motherboard, not the CT60).
And yes, the speed boost is very good without SV. Since SV, I don't use the speed boost. Watch your SCSI reliability if you want experimenting with the boost! (mine had problems at some 060 clock speed)

I would like to do this mod: http://joska.duckdns.org/dsp/ as well but I find the instructions to unclear. Is there any chance you could clarify this in more detail since you have performed the mod? Thx

Specifically I find the 'piggybacking' part unclear, I can understand the soldering to the capacitor though.

I have done this mod, and didn't see much difference in speed, so i reverted back to 32Mhz.

[wongck]

I have done this mod, and didn't see much difference in speed, so i reverted back to 32Mhz.

Unless you have an application that is choking the DSP, speeding it up will not see noticeable improvement.
The DSP can probably handle all current application available now, without any speed increase.

[paul92706]

I have done this mod, and didn't see much difference in speed, so i reverted back to 32Mhz.

Unless you have an application that is choking the DSP, speeding it up will not see noticeable improvement.
The DSP can probably handle all current application available now, without any speed increase.

I agree wongck!, so an't much use to boosting it up to 50Mhz.

[mikro]

The biggest gain is of course from the bus acceleration, it's one hell of a difference if your data travel to/from ST-RAM 25% faster. The DSP is usually just a bonus (and makes sense mainly because the CPU is also 25% faster) but I could really notice it when programming the DSP.

[stormy]

The biggest gain is of course from the bus acceleration, it's one hell of a difference if your data travel to/from ST-RAM 25% faster. The DSP is usually just a bonus (and makes sense mainly because the CPU is also 25% faster) but I could really notice it when programming the DSP.

Ah okay. Well if you find a way to boost the bus please let us know.

[joska]

I have done this mod, and didn't see much difference in speed, so i reverted back to 32Mhz.

Unless you have an application that is choking the DSP, speeding it up will not see noticeable improvement.
The DSP can probably handle all current application available now, without any speed increase.

That mod was *very* noticable back in the day when using the DSP to depack jpegs. Depacking jpegs was 50% faster at 50MHz compared to 32MHz. Of course, that's irrelevant when using a CT60 which is faster than the DSP anyway.

Another application that benefited from this was Apex Media.

[mikro]

I've just dug up some ancient numbers and benchmarks. So just FYI, having CT60@72 MHz with 25 MHz data bus is equivalent to have CT60@100 MHz with 16 MHz databus in real use cases (like rendering 3D scene).

[wongck]

Yes, it would be noticeable if there are a stream of data being push to the DSP and not starving it.
Nevertheless, it would great to have an additional processing unit in the system that one can use.\

I did not use the DSP JPEG processing much, IIRC, it can only decompress certain size JPG.

[joska]

I did not use the DSP JPEG processing much, IIRC, it can only decompress certain size JPG.

The Brainstorm/Atari jpeg decoder can decode any jpeg. It also decodes them straight to Atari 16 bit format, which is very handy on the Falcon IIRC even with the Afterburner the DSP+CPU decoding was faster than just CPU.

[wongck]

Thanks for correcting me.

I remembered reading a doc on a DSP JPEG decoder and it mentioned something like 24bits 320 x200 JPEG.
Not sure where or which document was that, may be the one from Atari.

[joska]

I remembered reading a doc on a DSP JPEG decoder and it mentioned something like 24bits 320 x200 JPEG.
Not sure where or which document was that, may be the one from Atari.

Correct, but that was just given as an example of depacking speed.

[stormy]

Mikro are you saying that the bus speed mod could be possible? Is this pie in the sky?

[mikro]

Well, there's no reason why it shouldn't -- you can install Nemesis or Phantom in your Falcon anytime. :)

The main reasons why I'm a bit hesitant with the CT60e:

1. I'm not sure whether it ever been tested by Willy
2. Whether it's the best route to take -- Ctirad (he has the same nick here on AF) has been thinking for a 'next gen' Phantom for years and if he ever gets to do it, this would be *the* thing to do, regardless of anything the CT60e can offer (i.e. it would be a rock solid clock patch for accelerated bus -- totally not guaranteed with Exxos' clock patch -- and accelerated motherboard to 25/50 MHz)

[DarkLord]

Isn't that what the motherboard mods "back in the day", did for the Falcon
anyway? Acting like a Nemesis or Phantom?

I'm pretty sure my Falcon's MB has the bus accelerated as well as the DSP
, etc,....

Never had a problem with it that I can tell.

PS This is with the original CT60 series though, and a CTCM.