Falcon is freezing in demos

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exxos
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Re: Falcon is freezing in demos

Post by exxos » Thu Sep 06, 2018 7:30 pm

KyleB wrote:
Thu Sep 06, 2018 6:51 pm
I don't think you'll get the full truth until you build one of these two chip phantom ones. I'm doing it in next couple of days but I don't have a scope.

It is unlikely I will ever get time to build that up, ideally I would have to try with the accelerator as well, and it just isn't high up on my to do list I'm afraid.
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derkom
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Re: Falcon is freezing in demos

Post by derkom » Thu Sep 12, 2019 9:35 am

I've come across a Falcon motherboard (actually a C-LAB MKII board) that is exhibiting the same initial symptoms as in the first post in this thread (crashing in demos). I've installed exxos' RTC/NVRAM no problem, but of course this has not affected the crashing.

DMA2DSP.PRG from mikro's f030test.zip seems to produce no output at all, red or green. The Maggie 24 intro recommended by dhedberg earlier in this thread produces only a black screen, as he said it would in the event of DSP problems. The diag cart (thanks exxos!) shows red screen at DSP SRAM failed. And the clincher, in my eyes at least, is DSPTEST, which reports "D15-D8 (U48) : BAD" (the other two chips report OK). This test fails on both a cold board and a warm one.

I pulled up the schematics and I have verified that every trace on U48 is connected where it should be. I tested most of them simply for continuity to the same pins on the other SRAM chips, since most of the pins are connected in parallel. The individual data lines I checked back at the DSP. I also visually inspected the board on both sides, and there is no evidence of any damage. (Some of the C-LAB modifications look a little rough, but they shouldn't be affecting this regardless.)

Is this enough diagnosis to declare the U48 chip bad and replace it? Will this finally be the impetus for me to learn how to do surface mount work? (Don't worry, if I go this route, I'll be doing lots and lots (and lots) of practice on junk boards before considering touching the Falcon.)

I notice at Mouser that the slowest chips offered today are 20 ns, where the Falcon has 25 ns chips. Is it okay to drop a 20 ns chip in there, or will I need to acquire a 25?

Side note: When running the diag cartridge, I'm getting other errors that are obviously related to not having the loopback hardware plugged into the various ports. But one error that worries me a bit is "EXTCLK opens, or VIDEL chip fails / MONO, or PRTACK stucks low" (see attached screenshot). I've never used the Falcon diagnostic before, and I don't have another working Falcon to compare to. Is this an expected error when testing without the loopback hardware, or is something else wrong with this Falcon?
Attachments
DSP-SRAM-test.jpg
DSP-SRAM-test.jpg (46.79 KiB) Viewed 96 times
IMG_20190912_111810.jpg
IMG_20190912_111810.jpg (69.35 KiB) Viewed 96 times

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Re: Falcon is freezing in demos

Post by exxos » Thu Sep 12, 2019 10:09 am

Loopback tests will fail without the proper cables.

I know a few people who had issues with the SRAM and had to change it. 25ns to 20ns shouldn't matter.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

derkom
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Re: Falcon is freezing in demos

Post by derkom » Thu Sep 12, 2019 10:16 am

exxos wrote:
Thu Sep 12, 2019 10:09 am
Loopback tests will fail without the proper cables.
Well I knew that... :lol: Just wasn't sure if that one error was one of the expected ones.

Thanks for the tip on the RAM. I figured faster is safe, but wanted to be sure before I consider putting a lot of effort into it. :)

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