Getting a TF536 working on my Mega ST.

[exxos]

Your scope is on 20MHz limit ? So with the clock being 50MHz...

[PhilC]

My scope will do 200mhz.

With a 1k8 pullip on clk and the 200pf between clk and gnd we nearly get to desktop. Freezes at busy bee

[exxos]

My scope will do 200mhz.

With a 1k8 pullip on clk and the 200pf between clk and gnd we nearly get to desktop. Freezes at busy bee

no cap...

your scope says BW limited to 20mhz.

[PhilC]

My scope will do 200mhz.

With a 1k8 pullip on clk and the 200pf between clk and gnd we nearly get to desktop. Freezes at busy bee

no cap...

your scope says BW limited to 20mhz.

Yeah realised that after, no the limit isn't set as active,.

With no cap it won't boot

[exxos]

Maybe try 50pf then ?

[PhilC]

Maybe try 50pf then ?

Ok, so without the 1k8 pullup I tried 50, 100, 150 and 200pf between clk and gnd. I can try those again with the pull-up in place?

The higher the cap loading, the better it booted but it then gives shifter errors with shifted bitplanes.

[DoG]

Just ran TF536 on my Mega ST.

Fixes/tweaks/upgrades done on my Mega:
I have IMP chip on both DMA and Shifter. Pullup fix on DMA. I have upgraded to 4Mb and they are 60ns. I have changed resistor arrays on databus (4.7k) and adressbus (3.3k). Running with a MeanWell RT-65B PSU. Using my newly made TOS256k decoder board and ROM adapter boards to run EmuTOS 0.9.12. ROMs are AT29C010A 90ns. Blitter is removed and deactivated.

Ran only with MAPROM.PRG in AUTO folder. Also set the flags on GemBench to run in ALT-RAM. Both program found on @agranlund github or site. Ran from floppy/gotek.

TF536 setup.jpg

TF536 gembench 6.8 EmuTOS 0.9.12.jpg

[PhilC]

Different shifter and DMA to what you have @DoG and my ram is pretty slow at 120ns one bank, 100ns the other. May be my 120ns isn't helping.

[PhilC]

Actually, bit of progress. The cpu I've been using is good for tedting but gets too hot for me to be able to sell it. So ive changed it with another I got in the post today and it gets to desktop but then 11 bombs each time.

The screen flickers like crazy as below, so I'll try a little less capacitance on the 8mhz line in a mo.

20200722_173025.jpg

[PaulJ]

Whats looking bad is the presumed 50MHz cycles which look like the scope probe are loading it to much. looks like you are on x10 already though ?

Yes, new probe freshly calibrated too.

Putting 200pf on clk to gnd makes it get to ram check but it crashes after a lot of Xs

@PhilC , did you do the probe compensation or is that what you mean by calibrated?