exxos blog - random goings on

[Icky]

[Icky]

Does make you wonder why nobody at Atari did this back in the day.

I think back in the day the components weren't as stable / fast as we have today. They were probably pushing the limits of things back then and any additional speed would have made the systems unstable.

I am sure Atari were aware of what was possible. As any R&D team would do they would of pushed it to the limit but in the end a production stable system would need to be turned down.

[exxos]

RAM is always expensive as well...

on loop 27 now

[exxos]

I don't think we are even maxing out the MMU...

Its not even slightly warm and its been pushing 32MHz for the past hour or so now...

Wonder if this would clock at 64MHz

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[PhilC]

Wonder if this would clock at 64MHz

Willing to bet we shall be finding out shortly

[exxos]

Wonder if this would clock at 64MHz

Willing to bet we shall be finding out shortly

When I get the proper mod pcbs done, I will try it, but while the MMU may clock that speed, the GLUE is likely going to be the spanner in the works.

Ultimately, It would be good to have a FPGA core which includes MMU,GLUE,BLITTER. Though these cores are not 100% accurate, so even 8MHz modes are going to break stuff.

Probably the way to go is a future board to have the normal ST chipset, with a huge expansion header to replace those with the FPGA cores. Then the user can decide if they want max speed or max compatibility. This is assuming the suska cores. Ijor has another set of cores, but AFAIK they haven't been tested a great deal or are open source.. Similar with the suska cores, in that I don't think they have had much testing by anyone on a original setup. I know the suska core doesn't "support" wake up states, as Troed and I found out, his demos won't run on the suska cores.

Also FPGA cores mean people can add features or updates to them. I talked to Wolfgang last year about a tweak to the MMU core.. to basically allow a "fast block clear" direct to RAM. In that the CPU only sets start,end address, and block fill pattern. The MMU can clear a block of ram without involving the CPU or blitter for the actual data clearing. Tweaks to games or the OS could be done to use such a feature. As games use a lot of clearing , it should increase frame rates even on a stock 8MHz setup... Really just thinking out loud, but I think tweaking the cores to allow new features is a interesting idea...

[exxos]

First mock-up of the Alpha 16MHz mod board...

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[exxos]

Pretty much this really I think...

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[exxos]

2600 RGB kit come

Now to find some time to build it all up.....

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[exxos]

I have transplanted my board into a more secure location..

Oddly it started being unstable again.. But placing a 50pF capacitor on the 32Mhz input to the mod board seems to have solved it.. I think the oscillator I am using is not very good... It seems to have something like a 0.9V DC offset for some reason. So I am going to remove this and use the proper 32MHz oscillators I got and see what the output is like on those.

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EDIT:

Some screw screwups

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Now I had to remove the 50pF cap to get the video to work right. Voltages on the osc are now good, about 0v - 3V.