TT Rom access speedup

Various tweaks and fixes from video ghosting to audio fixes etc.
Atarian Computing
Posts: 329
Joined: Tue Aug 22, 2017 4:27 am

Re: TT Rom access speedup

Post by Atarian Computing » Fri Mar 08, 2019 10:30 am

guus.assmann wrote:
Fri Mar 08, 2019 10:12 am
In a TT with Eproms, the OE line will be jumpered to GND, so OE is not used in the selection of the Eprom.
And it does need CS to work.
I have been looking at the data sheet of the 1N58189 but cannot find a recovery time.
That may be an important factor.
I have already had the TT not booting when I had one Germanium diode and a BAT48 (Si).
Unfortunatelly, the Germanium diodes I used had no partnumber.

I will do some more tests this weekend.

BR/
Guus
Ok, thanks again. I measured the voltage drop on both 1N5819s to be 0.22v. So should be fine if germaniums work. So yeah, it must be something other than switching speed.

Josh.

Atarian Computing
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Joined: Tue Aug 22, 2017 4:27 am

Re: TT Rom access speedup

Post by Atarian Computing » Fri Mar 08, 2019 3:18 pm

Ok guys. It was the ROM speed. I created a new set of ThunderStorm roms on 100ns chips. Took awhile because I changed the keyboard table.

Happy to announce that the speedup mod works great now! Here are some shots.

This is before the mod on new chips:
Before.gif
Before.gif (12.76 KiB) Viewed 748 times

This is after the mod on new chips:
After.gif
After.gif (12.45 KiB) Viewed 748 times

This is "after vs before":
After vs Before.gif
After vs Before.gif (12.19 KiB) Viewed 748 times

And this is "after vs before (old chips) with NVDI":
After vs Before NVDI.gif
After vs Before NVDI.gif (12.73 KiB) Viewed 748 times

Quite surprising results and gains it seems. Nice and simple mod. Thanks guus!! :dualthumbup:

guus.assmann
Posts: 73
Joined: Sat Sep 23, 2017 8:52 pm
Location: Ede Netherlands

TT Rom access speedup

Post by guus.assmann » Fri Mar 08, 2019 5:04 pm

Just now I've also tested with the 1N5819 diodes. And that also works just fine.
Then I removed the CF-cards so the TT would boot from floppy.
Attached are the result files.
Quite similar to the pictures in previous post.
I've only looked at the Rom speed while I compared the before and after.

The access to the Rom has influence on many results.
It's some measure of how often the Roms are accessed for the various functions.

U116 has an influence on the final speed as it's clocked with 16Mhz to pass on the DTACK signals.
My Epoms are all 120nS (2 TT's) and I've also got 90nS Flash Roms in a 3rd one.

P.S: How did you make the nice Gif's?

P.P.S: Do I see correctly that the results with NVDI are a little slower?
This would mean that the TT-Ram in the system is slower than the Rom.
Attachments
SLOW.TXT
(1.29 KiB) Downloaded 19 times
FAST.TXT
(1.29 KiB) Downloaded 19 times

Atarian Computing
Posts: 329
Joined: Tue Aug 22, 2017 4:27 am

Re: TT Rom access speedup

Post by Atarian Computing » Fri Mar 08, 2019 6:09 pm

guus.assmann wrote:
Fri Mar 08, 2019 5:04 pm
Just now I've also tested with the 1N5819 diodes. And that also works just fine.
Then I removed the CF-cards so the TT would boot from floppy.
Attached are the result files.
Quite similar to the pictures in previous post.
I've only looked at the Rom speed while I compared the before and after.

The access to the Rom has influence on many results.
It's some measure of how often the Roms are accessed for the various functions.

U116 has an influence on the final speed as it's clocked with 16Mhz to pass on the DTACK signals.
My Epoms are all 120nS (2 TT's) and I've also got 90nS Flash Roms in a 3rd one.

P.S: How did you make the nice Gif's?

P.P.S: Do I see correctly that the results with NVDI are a little slower?
This would mean that the TT-Ram in the system is slower than the Rom.
JML-Snap is what I use. Released as freeware by the author. See attached.

It's an NVDI result compared to an NVDI result. What you're seeing (I assume) is a smaller gain than without NVDI.
Attachments
snap_522.rar
(46.21 KiB) Downloaded 16 times

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Icky
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Re: TT Rom access speedup

Post by Icky » Sat Mar 09, 2019 7:48 pm

I need to do this on my TT too. Finding time is the problem.

Thanks for sharing guss :thumbup:

tuxie
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Joined: Thu Aug 24, 2017 11:51 am

Re: TT Rom access speedup

Post by tuxie » Sun Mar 10, 2019 11:20 am

Guus, when you load the TT default values, then you can compare to a stock TT with all Stock!

tuxie
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Re: TT Rom access speedup

Post by tuxie » Sun Mar 10, 2019 11:27 am

With a new TOS decoder you will get more then 30% more Speed on the Rom access. I have measured on my TT 197% Rom Access with 16Mhz Bus. With the 48Mhz CPU its almost 230%. But yes with that little trick you can archive already a lot . Own address decoder means own CS and xds0 / XDS1 Signal.

Steve
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Re: TT Rom access speedup

Post by Steve » Sun Mar 10, 2019 11:47 pm

Hey Atarian would it be possible for you to post a simplified guide with some mobo photos to help? Thx

Also is it possible for me to find out what speed my thunderstorm roms are? I can't program roms so it might be problematic for me.
Falcon ct60e 060 - 256mb ram - phantom bus and dsp accel // Atari TT - Thunder and Storm IDE 64mb ram - Lightning VME - USB LAN - Ati Mach64 2mb // Atari STM 4160 - 4MB ram - 16Mhz exxos 1.5 booster - Ultrasatan

Atarian Computing
Posts: 329
Joined: Tue Aug 22, 2017 4:27 am

Re: TT Rom access speedup

Post by Atarian Computing » Mon Mar 11, 2019 9:50 am

Steve wrote:
Sun Mar 10, 2019 11:47 pm
Hey Atarian would it be possible for you to post a simplified guide with some mobo photos to help? Thx

Also is it possible for me to find out what speed my thunderstorm roms are? I can't program roms so it might be problematic for me.
Sure, I can make a guide. I just need to finalize my custom ROMs and install them before I can do that.

You'd have to scrape away the sticker to reveal the chip details from one of the chips. No other way around it I'm afraid. But there are many variables involved so I wouldn't discount 150ns ROMs even though they didn't work for me.

guus.assmann
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Joined: Sat Sep 23, 2017 8:52 pm
Location: Ede Netherlands

TT Rom access speedup

Post by guus.assmann » Mon Mar 11, 2019 6:26 pm

Hello,

Here's a picture of the 2 diodes on pin 15 and 16.
The grey wire goes to the Eprom-CS at pin 22.
That's all there is to it.

BR/
Guus
Attachments
TT_Rompatch.jpg
TT_Rompatch.jpg (223.06 KiB) Viewed 628 times

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