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TMS9900 CPU core creation attempt


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#76 TheMole OFFLINE  

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Posted Wed Sep 6, 2017 2:05 PM

Great to see you're still at it, would love to see this come to fruition! :)



#77 speccery OFFLINE  

speccery

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Posted Wed Sep 13, 2017 2:30 PM

https://hackaday.io/...75-almost-there

 

The above link takes you to the current update - I finally had some time to really debug this thing and made good progress! We're getting really close to having the TI-99/4A completely implemented on the FPGA!



#78 speccery OFFLINE  

speccery

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Posted Wed Sep 13, 2017 2:34 PM

And here is the spoiler: video output of the TI ROMs running on the FPGA TI-99/4A implementation!

My TMS9900 CPU on the FPGA for the first time renders the boot picture properly!


#79 speccery OFFLINE  

speccery

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Posted Sun Sep 17, 2017 12:31 PM

Like many of you probably have seen in the Facebook updates, I did get the TMS9900 core working and I've been able to run a bunch of games on it.  

I need to fix the keyboard repeat rate issue before testing it much more, since typing at the moment is nearly impossible - with the CPU running 15x the speed of the normal TI, the repeat triggers way too fast.

I also want to add a register which would show me how many cycles the instructions take, as I want to optimise the CPU core further - need to go faster :)

 

Update at hack-a-day: https://hackaday.io/...ti-994a-working



#80 speccery OFFLINE  

speccery

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Posted Sun Sep 17, 2017 1:46 PM

Keyboard repeat problem fixed, at least partially. 

https://hackaday.io/...problem-and-fix



#81 speccery OFFLINE  

speccery

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Posted Sun Sep 17, 2017 2:47 PM

And next I tweaked memory timing, increasing the performance to 23x faster than the original TI:

https://hackaday.io/...riginal-ti-994a



#82 speccery OFFLINE  

speccery

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Posted Wed Sep 20, 2017 3:34 PM

The adventure continues, with adjustable CPU speed. The range just ain't enough yet...

 

https://hackaday.io/...eeded-and-added



#83 Sinphaltimus OFFLINE  

Sinphaltimus

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Posted Wed Sep 20, 2017 5:22 PM

The adventure continues, with adjustable CPU speed. The range just ain't enough yet...

 

https://hackaday.io/...eeded-and-added

 

 

Oh wow, my Zombi game might actually be playable with this board! Just gotta flip a switch when there's 4 or more zombies on the screen... LOL

Seriously, this is awesome. If you could get one dip switch to bring it down to real ti speed when needed... *THUD*

A true wizard!



#84 speccery OFFLINE  

speccery

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Posted Fri Sep 22, 2017 5:35 AM

 

 

Oh wow, my Zombi game might actually be playable with this board! Just gotta flip a switch when there's 4 or more zombies on the screen... LOL

Seriously, this is awesome. If you could get one dip switch to bring it down to real ti speed when needed... *THUD*

A true wizard!

 

 

I can't remember if your Zombi game was already downloadable from somewhere, that actually would be a really cool test.

Although I have tested extended basic and it works, I have not tested memory expansion (i.e. access to 32K of RAM) yet. I assume it works and that my Basic test program already used it, but haven't tested that yet. I also haven't tested loading of programs either - it will be interesting to see if my disk support built for the TMS99105 version directly works.

 

I need to expand my wait state counter further so that it can slow the processor down to real TI speeds, probably about 150 wait states per memory access would bring it close. Actually it is relatively straightforward to model the behaviour of real TI when it comes to memory access speed. It is an entirely different exercise to build a cycle exact CPU - that was never my goal, actually my goal was to build a very fast TMS9900 clone. To that end I have a few very simple ideas I want to try out, to increase speed from the measly 23x speed to something faster  :-D


Edited by speccery, Fri Sep 22, 2017 5:36 AM.


#85 Sinphaltimus OFFLINE  

Sinphaltimus

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Posted Fri Sep 22, 2017 11:25 AM

It's unfinished until I get work my way back to it but level 10 I think is a good test as the entire screen is filled with Zombies. Slows the game to being unplayable which is whee my reworking comes into play.

http://atariage.com/...bi#entry3693193



#86 Tornadoboy OFFLINE  

Tornadoboy

    Star Raider

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Posted Fri Sep 22, 2017 3:53 PM

This is sooooo awesome and so badly needed! 






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