AEH60 RISC PC Econet card hardware bugfix?

At the risk of eliciting a “why the bloomin’ ’eck are you trying to do that?!”

I’ve picked up an AEH60 Econet card for my RISC PC. I’ve found that it works okay (most of the time) when used as a client, but not so well as a server (using Level 4 or Advanced Level 4)

I can *Cat directories and write files from any other machine on the Econet to the RISC PC, but trying to read files from the RISC PC Fileserver results in a “Station 123 is not responding” or “No reply” error.

I’ve read that there was a hardware bug on the card which was later resolved by Acorn accepting them back for modification. Does anyone know the details of this fix?

Or if someone has one which was used in a working server — could you possibly take it out of your Risc PC and take some photos? :D
*RomModules output would help too, though I expect this is a hardware patch and not a ROM fix.

I understand Carl Elkins at Acorn was involved in getting cards sorted “back in the day”, though I’ve not been able to find an email address to ask if he still remembers the details. If anyone does, please feel free to link him to this post!

Cheers
Phil.

I’ve read that there was a hardware bug on the card which was later resolved by Acorn accepting them back for modification. Does anyone know the details of this fix?

I’ve looked at my AEH60 and can’t see any evidence of a modification (eg. wire mods, flux near solder joints) and the PAL/EPROM look original too (circa 1994). I’ve not seen any ‘No reply’ type errors, though the Risc PC was the client of an A5000 server so wasn’t going at particularly high speed. What happens if you slow the clock down?

I understand Carl Elkins at Acorn was involved in getting cards sorted “back in the day”, though I’ve not been able to find an email address to ask if he still remembers the details.

I don’t think Carl lives around Cambridge any more, last time I tried to get in touch he was oop north somewhere.

> What happens if you slow the clock down?

Same problem. I took it right down to a 12us period, though I kept the mark time at 1us. It was slow as molasses but still had problems.

There’s never a problem in client mode, only when running Level 4 or awServer.

If I play with the delays in the Advanced Level 4 demo, I can make it kinda-sorta work, but the RISC PC crashes after a few files are transferred.

I was hoping to use the RISC PC as a bridge between Econet and Ethernet, though if I can get my hands on an Ethernet mini-Podule I can probably use the A4000 for that.

Not aware of any hardware fixes but there was a software fix in the 3.7 ROM to allow it to run on a StrongARM. I don’t think it was in the 4.02 ROM so I had to softload it.

If I can find the card I will have a look at it though.

We’ve figured this one out over on Stardot — turns out Acorn made a mistake on the RISC PC Econet card (all three we located have the bug).

There’s a 74HCT123 timer on the board which is used to implement the transmit timer (aka “babble timer”). The goal is to stop a station from staying in transmit for more than a couple of seconds.

In every other Econet card this chip is a 74LS123 — which has significant differences in behaviour. For one, it only needs a brief reset pulse to reset the timer. The other is the delay on the LS123 is much shorter with the same components. There’s a root-cause analysis on Stardot if you’re interested: https://stardot.org.uk/forums/viewtopic.php?f=7&t=19428&p=276812#p276674

Long story short, swapping the 74HCT123 for a 74LS123 fixes the card. :)