Request for testers for quick but fascinating test case

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BeebMaster
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Re: Request for testers for quick but fascinating test case

Post by BeebMaster » Mon Oct 07, 2019 5:06 pm

Oh yes! Well, fair enough then. I've taken a new picture of Station 129's motherboard today, if anybody needs a more detailed picture I'll upload it to my website when the film is back from the chemist's and link here.
Image

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scarybeasts
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Re: Request for testers for quick but fascinating test case

Post by scarybeasts » Mon Oct 07, 2019 6:47 pm

BeebMaster wrote:
Mon Oct 07, 2019 2:38 pm
It boils down to whether the disc drive ribbon cable is plugged into the disc drive port at power-on or not:
Plugged in: 2/1
Not plugged in: 1/1

Changing this (ie. plugging or unplugging the cable) whilst powered on makes no difference to the result, it is the same from power on until the next power on no matter what.
Thank you.
And, ah, goodness me -- that is quite the crazy result!

This does seem to confirm cycle stretching differences are observable on issue <= 3 machines. The timing of my test case is pretty tenuous it seems.


Cheers
Chris

steve3000
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Re: Request for testers for quick but fascinating test case

Post by steve3000 » Mon Oct 07, 2019 9:17 pm

I've just tried this on my issue 3 beeb, several times and I am occasionally getting different results.

Usually VSIRQTM gives 2/1 but sometimes I get 1/1

Once powered up it always seems to give the same result if I repeat the test even with a reset and try again, but if I switch the computer off/on between tests, then sometimes the result changes.

I don't have a disc interface on this beeb, just the base model B spec with a userport SPI SD card interface.

Coeus
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Re: Request for testers for quick but fascinating test case

Post by Coeus » Mon Oct 07, 2019 9:54 pm

Ok, I don't think you've had this one in the results yet.

BBC B, Issue 7, but with a R65C02 in place of the usual NMOS 6502: 2/2
On my Master with VTI 6845: 255/255

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Re: Request for testers for quick but fascinating test case

Post by marcusjambler » Tue Oct 08, 2019 4:41 pm

BBC B Issue 7 with new Integra B and VNula

2 Cycle Stretch : 255
3 cycle stretch : 255

I cant see the IC idents cos I stuck heatsinks on :D

And...

BBC B Issue 3 HD6845SP SY6502A SY6522

2 cycle stretch : 2
3 cycle stretch : 1

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SpaceFlightOrange
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Re: Request for testers for quick but fascinating test case

Post by SpaceFlightOrange » Fri Oct 11, 2019 6:38 pm

BBC A (upgraded) Issue 3 SYS6502a, HD6845SP, SY6522 (IC3), Rockwell R6522-33 (IC69), SY6502A, IFEL ROMRAM B4, running the ULA from my Master

2 CYCLE STRETCH: 1
3 CYCLE STRETCH: 1

BBC Master (not open) VNULA

2 CYCLE STRETCH: 255
3 CYCLE STRETCH: 255
James

BBC Model A Issue 3 (Upgraded to Model B, had it since I was a kid), Opus Dual 40/80 FDD, Watford Mouse, Voltmace delta 14/B, Gotek, IFEL ROMRAM-B4, Pi-Zero CoPro

Master 128, VideoNuLA, Gotek

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scarybeasts
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Re: Request for testers for quick but fascinating test case

Post by scarybeasts » Wed Oct 30, 2019 11:01 pm

In case anyone was interested in why the same machine would differ in behavior from boot to boot, I think I worked it out.

I was curious enough to buy a simple scope. Turns out there's a very interesting hardware quirk. I've given the details in this new thread in hardware: viewtopic.php?f=3&t=18174


Cheers
Chris

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