DEC KA650 VAX memory troubleshooting (video)

[Rob Jarratt]

Thanks, I am aware of BitSavers of course, so I am not sure why I didn’t think to look there!

 

Regards

 

Rob

 

From: Joe Zatarski <joezatarski at gmail.com> 
Sent: 16 June 2019 15:39
To: rob at jarratt.me.uk
Cc: General Discussion: On-Topic Posts <cctech at classiccmp.org>
Subject: Re: DEC KA650 VAX memory troubleshooting (video)

 

sorry, the technical manual actually, which has an architecture *chapter* http://www.bitsavers.org/pdf/dec/vax/650/

 

The idea, eventually, is that I will publish my notes so that you wouldn't need the logic analyzer, at least for the 8MB board. I just had it hooked up, so I demoed it. The notes will include a mapping of bits and adresses to ICs so that you can narrow down which chip from just the ROM monitor. I don't have a 16MB board, but somebody could honestly probably figure out the mapping with a logic probe if they had to, just probe /cas while writing various test addresses, then check the data line while writing various test patterns. I also came up with some data that produces useful ECC bits, like all 1s, all 0s, one bit set only, and one bit clear only. That will also be in the notes when I write it up.

 

On Sun, Jun 16, 2019, 3:25 AM Rob Jarratt <robert.jarratt at ntlworld.com <mailto:robert.jarratt at ntlworld.com> > wrote:

That is really interesting, sadly I don't have quite as much gear as you, I only have a basic logic analyser, but I am not currently trying to fix a MS650 memory board. You mentioned a KA650 architecture manual and you had a PDF of it in the video. I couldn't find it on Manx? Where can I find it?

Thanks

Rob

> -----Original Message-----
> From: cctech <cctech-bounces at classiccmp.org <mailto:cctech-bounces at classiccmp.org> > On Behalf Of Joe Zatarski via
> cctech
> Sent: 16 June 2019 02:33
> To: cctech at classiccmp.org <mailto:cctech at classiccmp.org> 
> Subject: DEC KA650 VAX memory troubleshooting (video)
> 
> Hey Everyone,
> 
> I just thought I'd share a video of how I'm going about troubleshooting the
> bad DRAMs on my MS650 memory board.
> 
> https://youtu.be/eDMhdAEFEgc
> 
> I apologize for the shaky-cam, I don't have a tripod, and I needed to do a lot
> of panning anyway.
> 
> I will be sharing my notes on the MS650 once I have a chance to write them
> up properly as well. I wasn't able to find a printset for the RAM card itself, so I
> assume one doesn't exist in digital form yet. I have documented what bit and
> memory range each DRAM on the card corresponds to, which may help
> someone troubleshooting in the future
> 
> Regards,
> Joe Zatarski