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Re: TT Rom access speedup
Posted: Thu Mar 07, 2019 8:11 pm
by Atarian Computing
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 (175.36 KiB) Viewed 6123 times
Re: TT Rom access speedup
Posted: Thu Mar 07, 2019 8:25 pm
by Steve
Once Atarian has an easy to follow guide I will do this in my TT as well
And maybe the FPU overclock too.
TT Rom access speedup
Posted: Fri Mar 08, 2019 8:01 am
by guus.assmann
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
Re: TT Rom access speedup
Posted: Fri Mar 08, 2019 9:17 am
by Atarian Computing
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.
TT Rom access speedup
Posted: Fri Mar 08, 2019 10:12 am
by guus.assmann
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
Re: TT Rom access speedup
Posted: Fri Mar 08, 2019 10:30 am
by Atarian Computing
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.
Re: TT Rom access speedup
Posted: Fri Mar 08, 2019 3:18 pm
by Atarian Computing
TT Rom access speedup
Posted: Fri Mar 08, 2019 5:04 pm
by guus.assmann
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.
Re: TT Rom access speedup
Posted: Fri Mar 08, 2019 6:09 pm
by Atarian Computing
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.
Re: TT Rom access speedup
Posted: Sat Mar 09, 2019 7:48 pm
by Icky
I need to do this on my TT too. Finding time is the problem.
Thanks for sharing guss
