TT FPU overclock

[dexterslab]

has anyone else overclocked their FPU on the TT?

as the FPU can have a clock completly separate from the main CPU/Bus clocks it's a pretty easy mod.

I have a 40mhz oscillator here to patch in through the W101 jumper that selects the FPU speed

will post pics & results

if only it was that simple for the CPU

[artik-wroc]

http://www.ataritt030.info/upload/dokum ... rclktt.txt

Never tried

[dexterslab]

aye, cool... that doc says 48mhz. I have 40mhz to start with so we'll see how it goes, oscillators are not expensive so easy to change.

@artik-wroc
can you credit me and link to my website for the megtt.zip file that you copied from my site?

[artik-wroc]

can you credit me and link to my website for the megtt.zip file that you copied from my site?

Sorry, but sometimes someone will send me something. I did not want to do anything against the will of the owner.
I will arrange the necessary changes.

[dexterslab]

can you credit me and link to my website for the megtt.zip file that you copied from my site?

Sorry, but sometimes someone will send me something. I did not want to do anything against the will of the owner.
I will arrange the necessary changes.

thats ok, i dont mind you putting them up... it's nice to have a credit and a link back to my own site!

[wongck]

How about someone putting up your work and commenting that it is something "not" to do .....

[dexterslab]

done... not earth shattering, but not bad for a £2 mod

Before

Code: Select all

Float multiply (64bit) -> 0.541 MegaFlops (~204%)
Float divide (64bit) -> 0.351 MegaFlops (~203%)
Linear (stalled) float -> 1.006 MegaFlops (~188%)
Interleaved (piped) float -> 1.003 MegaFlops (~188%)

After (40Mhz)

Code: Select all

Float multiply (64bit) -> 0.672 MegaFlops (~253%)
Float divide (64bit) -> 0.436 MegaFlops (~252%)
Linear (stalled) float -> 1.148 MegaFlops (~215%)
Interleaved (piped) float -> 1.147 MegaFlops (~215%)

[wongck]

done... not earth shattering, but not bad for a £2 mod

Before

Code: Select all

Float multiply (64bit) -> 0.541 MegaFlops (~204%)
Float divide (64bit) -> 0.351 MegaFlops (~203%)
Linear (stalled) float -> 1.006 MegaFlops (~188%)
Interleaved (piped) float -> 1.003 MegaFlops (~188%)

After (40Mhz)

Code: Select all

Float multiply (64bit) -> 0.672 MegaFlops (~253%)
Float divide (64bit) -> 0.436 MegaFlops (~252%)
Linear (stalled) float -> 1.148 MegaFlops (~215%)
Interleaved (piped) float -> 1.147 MegaFlops (~215%)

32 MHz to 40Mhz is 25% increase.
The float multiply & divide is scaled correctly by 25% so it's expected.
While linear & interleaved float is not so, probably 2 cycles is needed ??
They just increase by ~12% or half the jump.

[dexterslab]

yea, just wish i could do something with the cpu!

there's pics of the mod on my website, just needs connecting to 5v and GND, i made a jumper that attaches to the W101 FPU clock select jumper so i can select 32 or 40mhz using a jumper

[wongck]

Actually not bad for a £2 mod.
Will overclocking the CPU be so simple?

[simbo]

in the falcon 030 the nemesis works in high mode by giving 48mhz clock output
to the dma the dsp the fpu combel and mpu
the videl has its own clock @25mhz that also gets doubled to 50mhz
while the keyboard and midi controller chips need the clock moved from ?500khz to 500 and something else
cant remember
this keeps sync properly accross these periferal controllers

so in theory a similar board to the nemesis is possible even a moded nemesis
or better would be to send email to the maker of the phantom board
see if he can do one for the TT

adding a couple of heatsinks as needed is a good idea

i use 55mhz in the nemesis now and get 32mhz from the dsp older can
for low mode
using the 40mhz alternate clock on the nemesis as the medium range
i find boot in medium seems a balance
i get around 300% or so better fpu

i also think you need to check what fpu chip you have
if its a 68882-fn16 it will run slower that a -fn33 type when run at 40mhz or above
the fn16 is only ment to run at 16mhz
http://www.atari-forum.com/viewtopic.php?f=27&t=10409
i use 55mhz so i get around 200% basic acceloration
the pictures here are a little older
im just building a nicer case for it now...
the only problem i can see would be slow dram memory
i remember its 30pin simms at the ST ram section
so perhaps there would need be a mod to retro fit in a 72pin fastpage 60ns simm
as per the falcon .. etc..
as the nemesis must use fast ram or nothing not even a boot

[dexterslab]

i think it's less complex on the TT simbo, the CaTTermaran seems to just inject new clocks into a few places to overclock CPU/FPU to 48mhz and thats well proven, no extra boards or ram needed. The CPU/FPU is asynchronous to the main bus which does help.

Someone was going to look at reverse engineering the CaTTermaran, but it seems the project fizzled out

[joska]

while the keyboard and midi controller chips need the clock moved from ?500khz to 500 and something else

The keyboard- and MIDI-controllers are simple UARTs, and they need a 500kHz clock to generate the correct baud rate. Some ten years ago I ran my TT at 40Hmz simply by replacing the 32MHz oscillator and feeding the keyboard/MIDI-UARTs with 500kHz. It worked well, except that the video timing was way off so my VGA monitor could not display anything. It worked fine with the graphics card though, as is has it's own dot-clock.

I've also speeded up a Stacy to 12Mhz the same way, the LCD worked but was a bit dim due to the increased refresh-rate. It blew up when I tried to run the ADSpeed16 at 24Mhz though

so in theory a similar board to the nemesis is possible even a moded nemesis
or better would be to send email to the maker of the phantom board
see if he can do one for the TT

It's not so easy. The Videl you can adapt to the new clock, but this is not the case with the TT-shifter. You need to figure out a way to fix the sync-signals, or use a graphics card. There was a 12Mhz-project for the ST in C't many years ago, the sync-problems were fixed by adding a circuit that generated new sync-signals. Of course, a faster bus means that the shifter pumps out pixels faster, so you get more pixels on the screen

[wongck]

The keyboard- and MIDI-controllers are simple UARTs, and they need a 500kHz clock to generate the correct baud rate. Some ten years ago I ran my TT at 40Hmz simply by replacing the 32MHz oscillator and feeding the keyboard/MIDI-UARTs with 500kHz. It worked well, except that the video timing was way off so my VGA monitor could not display anything. It worked fine with the graphics card though, as is has it's own dot-clock.

Wow.... that's something.
A 25% increase in performance with 2 oscillator replacement seems a good bargain.
Why come out with a kit or something like that ?

[joska]

The keyboard- and MIDI-controllers are simple UARTs, and they need a 500kHz clock to generate the correct baud rate. Some ten years ago I ran my TT at 40Hmz simply by replacing the 32MHz oscillator and feeding the keyboard/MIDI-UARTs with 500kHz. It worked well, except that the video timing was way off so my VGA monitor could not display anything. It worked fine with the graphics card though, as is has it's own dot-clock.

Wow.... that's something.
A 25% increase in performance with 2 oscillator replacement seems a good bargain.

Not two oscillators, but one oscillator and a counter to divide the original 32Mhz clock down to 500kHz for the ACIAs.

Why come out with a kit or something like that ?

Because you can't connect a monitor unless you have a graphics card.

[wongck]

Because you can't connect a monitor unless you have a graphics card.

Well, at least it will be great for a good portion of the people with a graphics card.

[dexterslab]

@joska

very interesting you swapped the oscillator for 40mhz, i had looked at the TT schema and found the TTShifter using the 32mhz clock which also outputs it to U210 which generates a load of 16mhz clocks, so you might have found you where overclocking the whole system?

[joska]

very interesting you swapped the oscillator for 40mhz, i had looked at the TT schema and found the TTShifter using the 32mhz clock which also outputs it to U210 which generates a load of 16mhz clocks, so you might have found you where overclocking the whole system?

Yes, that's exactly what happens. The main oscillator is replaced, and the entire system is overclocked. To keep the keyboard and MIDI working I fed the ACIAs directly with a 500kHz clock, that's it. This is how it's done on the Falcon too, except that the Videl is a lot more flexible than the shifter and can generate the correct syncs despite the new system clock.

[wongck]

@joska

very interesting you swapped the oscillator for 40mhz, i had looked at the TT schema and found the TTShifter using the 32mhz clock which also outputs it to U210 which generates a load of 16mhz clocks, so you might have found you where overclocking the whole system?

So Mark, making your own Cattamaran?

[dexterslab]

hmmm

/rubschin

[wongck]

I am looking at your machine #2.... you have a spare TT to experiment on

[atarimusic[dot]net]

I'm just reading through this thread as I continue research for an article I'm writing on the Falcon's basic FPU here:
http://www.atarimusic.net/index.php/fea ... ris-g-spot

I just wanted to let you and anyone else reading this thread know, that although the Atari Music Network is primarily about music, if someone is inspired enough to create and sell a new booster kit for the TT or Falcon or any other hardware kit for that matter, you are always welcome to use my site to promote it on the front page. I will advocate anything related to Atari hardware/software development FREE.

Cheers!

[wongck]

I will advocate anything related to Atari hardware/softwarte development.
Cheers!

Oh really?
But you also redicule about others ppl attempts of hardware jobs on their machines and further comment that it should not be done that way.

[atarimusic[dot]net]

Yes, my site is full of parodies and humour but I'm certainly not out to offend you personally. Having said that, if one of your hardware mod-jobs is in that article anywhere, just PM me and let me know if it offends you and I'll be more than happy to take it out. Not everyone finds the same humour funny - I understand that.

My belief is that since these machines will never be made again, we have a responsibility as an "Atari care-giver", so to speak, to maintain them in their original states as much as possible. For example, last year, I didn't even know what an NVRAM was, let alone how to solder. When I starting researching it, I became discouraged at all these workarounds and taught myself soldering so I could renew all three of my Falcons back to their original working state. It took me 7 hours to solder each one because I was a beginner, but I learnt a new skill in the process! Faced with a the choice to completely replace an original component vs. using a band-aid solution, it's my opinion that we should aim to treat these machines like like a vintage sports car, although not everyone shares this viewpoint.

Anyways, I'm just letting folks know that if they go so far as to produce a professional hardware booster kit, they can have as much support as they want on my site. Right now, my site is receiving upto 300 clicks a day and I'm even paying Google Ads and Facebook ads to jump start activity on the site's forums. I'm very dedicated to keeping Atari alive in any way I can.

[Shredder11]

Yes it is probably just a cultural difference in humour, because I am from the UK (or England to be more accurate!) and I find the new Atari Music website to be very friendly and open.