TF534 with 50Mhz 030... doesn't like 50Mhz

[FluffyRedLobster]

Hi all,

After a bit of advice... I realise things have moved on from the 534 but I'm still messing with mine and it's mostly working great

So my 534 lives on a Rev6a A500 board and has a 50Mhz 030 sat atop it. No FPU. I believe the 030 is a genuine 50Mhz - although I'm only basing that on the fact that the part number is etched on the ceramic and I figure that must be more difficult to fake than models with the model number printed on the copper bit...

Workbench is stable at all speeds, but if I run it with a 50Mhz or 48Mhz oscillator, I get a lot of grief with whdload - mostly fairly random "Access Fault" or "Illegal Instruction" errors across the majority of games. All is good with a 40Mhz oscillator. So obviously the board isn't happy at 48 or 50Mhz. I've stuck a small heatsink on the top of the 030 but it didn't make any appreciable difference. Is there anything else I can try? Heatsinks on any of the other chips worth a go? Anything else I could tweak or experiment with? If not I'll just leave it at 40 as it seems solid as a rock there. Be nice to get that extra 10Mhz though

Oh, running the most recent firmware (18/02/2019) with all components as per the bom. Also have a boobip 2mb expansion in the trapdoor with the 0.5mb chip mem mod.

Any suggestions appreciated!

Cheers,
Chris

[terriblefire]

The later boards give the CPU a break by throttling down to 14/7Mhz when talking to slow buses.

Dont really know how to get the best out of your particular CPU.. Might even be your RAM is marginal at 50Mhz.

[FluffyRedLobster]

Cheers Stephen... In that case I think I'll leave it at 40Mhz and enjoy using it for a while

While I wait for the next big thing to build

[alenppc]

Yes, my experiences were similar. It really gets unstable past 40 Mhz but this is such a fast card that I really don't think you need to go past.

[EzdineG]

Yes, my experiences were similar. It really gets unstable past 40 Mhz but this is such a fast card that I really don't think you need to go past.

I built 2 of these and they behave the same way. 40mhz is the sweet spot in my anecdotal testing.

[edit] I’d like to point out that I really only saw instability with WHDLoad; general system usage never produced any issues.

[FluffyRedLobster]

Thanks guys, that settles it then - good to know it's probably nothing to do with my assembly techniques

Agreed alenppc, it's plenty fast enough at 40, especially with the MMU on.

EzdineG - same experience for me over 40, whdload is the only thing that gave me grief over that speed, everything else was spot on.

Thanks again for all the replies - you saved me several hours (days) of trying to coax a few more MHz out of the beastie!

Cheers,
Chris

[FluffyRedLobster]

So I couldn't leave it alone...

I found after extended WHDLoad play a little instability still creeping in at 40Mhz - apparently some kind of heat build up issue as a game like Speedball 2 would be solid as a rock for a couple of hours, then it (and everything else) would suddenly start crashing until the 500 was left powered down for a while.

So I've come up with a cooling solution. Since fitting this I've been able to run using a 48MHz oscillator without a single crash, even leaving it running various WHDLoad things almost an entire day

IMG_0281.jpg (81.83 KiB) Viewed 5858 times

Active cooling in 500, sacrilege. The fan is a Noctua NF-A4x10 FLX, comes with a bunch of adapters (the FLX bit) so it can be soldered straight to a 5v line without hacking off the header. It also has a low noise adapter which makes it - to my ears at least - pretty much silent. This was important to me as the 500 should be silent except for the dud-dud-dud of the floppy drive. It does feel a bit wrong to have a fan in there at all, but I'll take the stability... It's even been pre-yellowed so it will match the colour of the case in a few years time.

The placement of the fan means that the cpu gets the bulk of the airflow but the ram gets some too - scientifically proven by wafting a piece of tissue over them. It was also the only place it would fit and still allow the case to close.

With the fan running the CPU heatsink never gets more than mildly warm. Without it, after an hour or so it would get hot enough that you wouldn't want to touch it for more than a few seconds (and don't even think about touching the CPU without the sink)

That's it. Complete. For now.

[PaulJ_2.0]

This may well solve why I dont have problems at 50mhz.
I have a 5v raspberry pi cooler/heatsink on my card (powered from PWR1).
It's nice and low profile too, so it clears the case nicely.

https://www.ebay.co.uk/itm/153570075446

It doesn't look much but the cpu never even gets a little bit warm.

[FluffyRedLobster]

Oh, nice! That would work out considerably cheaper How’s the noise level?

[PaulJ_2.0]

Oh, nice! That would work out considerably cheaper How’s the noise level?

I cant hear it unless I put my ear down to it, but its got a little whoosh to it.