TT Rom access speedup

Various tweaks and fixes from video ghosting to audio fixes etc.
Atarian Computing
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Re: TT Rom access speedup

Post by Atarian Computing » Thu Mar 07, 2019 8:11 pm

guus.assmann wrote:
Thu Mar 07, 2019 5:41 pm
Hello Josh,

The Eproms from ThunderStorm are fast enough, mine are 150nS.
And 1N5819 should work, most important is the voltage drop. ( <0,8V)
However, CS is pin 20 and not pin 22.
Pin 22 is OE and that's permanently connected to GND trough one of the jumpers.
I have not seen any slow Eproms yet. But I've only tested on 3 TT's.
And I've used Germanium diodes. I could test with 1N5819 as well.

BR/
Guus

PS: Attached are the GB files with the speed data.
Ok, I'm confused. 27c010 pin 24 is OE and 27c1000 pin 2 is OE. Both have pin 22 as CS. Now 27c512 has pin 20 as CS and 22 as OE. 28pin 1mbit Mask rom has pin 20 as CS. How are your W601,W602,W603 jumpers set? Maybe you're using different eprom chips?
tt-roms.jpg
tt-roms.jpg (175.36 KiB) Viewed 346 times

Steve
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Re: TT Rom access speedup

Post by Steve » Thu Mar 07, 2019 8:25 pm

Once Atarian has an easy to follow guide I will do this in my TT as well :) And maybe the FPU overclock too.
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

tuxie
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Re: TT Rom access speedup

Post by tuxie » Thu Mar 07, 2019 10:05 pm

@guus could you please take a newer gem bench ? maybe that one from Exxos ? And without NVDI then you can see the huge differences

tuxie
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Re: TT Rom access speedup

Post by tuxie » Thu Mar 07, 2019 10:06 pm

AtarianComputing you have great schematics where did you got it ? Did someone a redraw :shock:

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exxos
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Re: TT Rom access speedup

Post by exxos » Thu Mar 07, 2019 10:29 pm

tuxie wrote:
Thu Mar 07, 2019 10:05 pm
@guus could you please take a newer gem bench ? maybe that one from Exxos ? And without NVDI then you can see the huge differences
The file says GB6...

But good point about NVDI... Routines are not using ROM access, but RAM & NVDI, so that will explain why he is getting "unexpected" results, as speeding up ROM with NVDI installed is a bit pointless..
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tuxie
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Re: TT Rom access speedup

Post by tuxie » Thu Mar 07, 2019 10:48 pm

Oh yes I see, but better to load the TT reference file!

Atarian Computing
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Re: TT Rom access speedup

Post by Atarian Computing » Fri Mar 08, 2019 4:03 am

tuxie wrote:
Thu Mar 07, 2019 10:06 pm
AtarianComputing you have great schematics where did you got it ? Did someone a redraw :shock:
Thanks :) I did. With KiCad. Bit of a wip still.

guus.assmann
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Location: Ede Netherlands

TT Rom access speedup

Post by guus.assmann » Fri Mar 08, 2019 8:01 am

Hello,

I am very sorry for the mixup I caused.
I confused 28 pin and 32 pin devices.
So it is indeed pin 24 that's the CE for the Eprom that I used.
I'll try with 1N5819 diodes, hopefully today.

As for the Gembench, I took the most recent version I could find.
And next I'll try without any extra programs loaded. (Rename the Auto-folder should do the trick)

BR/
Guus

Atarian Computing
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Re: TT Rom access speedup

Post by Atarian Computing » Fri Mar 08, 2019 9:17 am

guus.assmann wrote:
Fri Mar 08, 2019 8:01 am
Hello,

I am very sorry for the mixup I caused.
I confused 28 pin and 32 pin devices.
So it is indeed pin 24 that's the CE for the Eprom that I used.
I'll try with 1N5819 diodes, hopefully today.

As for the Gembench, I took the most recent version I could find.
And next I'll try without any extra programs loaded. (Rename the Auto-folder should do the trick)

BR/
Guus
No worries. Thanks for clearing it up. Although a slight confusion remains after your correction. Have you meant OE (Output Enable) all this time rather than CS/CE (Chip Select/Enable)? Because pin 24 is OE.

Josh.

guus.assmann
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TT Rom access speedup

Post by guus.assmann » 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

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