4 Meg Static ram issues

[Jay Cotton]

I have 3 of these 4Meg Static ram boards.  They all work with my PDP11 card as well as

the Z80 card.  All s100computers.com stuff.

One of these ram boards used to work with my xxu.  I used to run UNIX and Cromix.

At this time none of these boards works with the xxu.  

The xxu seems to be working with a 1meg Cromemco board.

As stated else where I have been trying to figure out why I can't boot UNIX or Cromix from

the hard disk image with (pdp8online) mfm emulator.  I can boot Cromix from a floppy

image and then mount the partitions from the hard disk.

Back to the ram.  The boot rom monitor memory test reports all of the ram as bad.

First, has anyone else seen this before, and should I be debugging the xxu card ?

Next,  I have not been able to find a schematic for the xxu/xmu cards.  Any ideas ?

tnx

jc

[Jay Cotton]

I did find the xxu schematic's  

jc

[Richard Muse]

I have seen this. I had a 4 meg board in my XXU system for quite a while. No issues. I let is sit for almost a year then when I tried to boot it, I got many ram errors. I swapped in a 2048KZ, which is faster anyway, and had no issues.

I have a 4meg board in another system with a DPU in it and it has been working fine for years. Even with some extended off time in between. I have not done anything to troubleshoot the 4Meg board I was using in the XXU system. Since you've mentioned this though, I'll try it in one of the other systems and see if it works as is.

I can't image what changed. The XXU is running 172 Cromix and V2.2 Unix. Both are fine with the 2048KZ.

I can boot both cromix and unix from the emulator. I have XDOS defaulting to STDC 32 to boot Cromix. My XDOS version is 02.04.

Unix boot is to STD31

After escape type bst1f at the semi-colon for Unix.

I have noticed that I have to let the XXU system sit turned on for a minute or so before letting it boot or the emulator sometimes fails with errors. I have a web based system I use to control all the machines and the 'On' for the XXU has a 45 second delay before releasing the reset. This often is not long enough though. Especially if it has been off long enough for the Capacitors to discharge on the Emulator. Which is most of the time. Interestingly, some times it boot just fine, even after a week or so.

Are you getting an error trying to boot directly to the emulator?

Richard

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[Jay Cotton]

refer to your screen shots.

After bst1f,  I get to the Size: message and a bit after the boot process stops.

Booting Cromix I get to the "System initialization complete" message and then

the boot process stops.  

I don't get any error messages at all.  My assumption has been  that there is a DMA completion

sequence that is not completing.

I have all the same h/w and software as you do.

The above is seen with a 1meg cromemco memory.

With 4meg static ram,  I get no where.  

Been looking at the s100 bus with a logic analyzer, nothing is jumping out as an obvious error or missing

signal.  

jc

[Richard Muse]

Hmm, so in Cromix boot no 

XXU Cromix-Plus release 172 

Welcome to XXU Cromix  

Login:

But you can boot to XXU Cromix from a floppy. Hmm again. Since you can mount the Cromix hard drive, I would say to check the /dev/console device and /etc/ttys on it to be sure /dev/console is 1:0 and console is enabled in /etc/ttys. Though you probably have done this already.

I assume you are using Marcus' Unix V2 image for the emulator. If so, that is how it is set up.

Does Cromix on the floppy let you specify the device you want to boot to or does it just default to the floppy?

Richard

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[Mike Stein]

Yeah, I'm thinking that there might be an issue with the device names/binary values but Jay checked and apparently not.

I can't check right now but ISTR that XDOS 1.xx (which is what Jay has) had some discrepancy between FDC drive letters, the XDOS values, and the table in the manual; seems to me I had trouble finding the right binary value for my STDC configuration. Version 2.xx makes it a lot clearer; I wonder whether it would be compatible with the different PALs etc. on the later board.

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[Jay Cotton]

Hi Mike:

Booting from STDC you need to use the hex value for the drive partition.  As far as I know, this is the only restriction.

The floppy boot code seems to be fine (for me).

So booting partition 31 from the hard disk image I am using bst1f .  And to be clear, it does boot unix, it just never finishes.

As I pointed out above, the static ram not working seems to be a smoking gun.  I did have a thought, I have not seen any discussion

about TMA0 or PHANTOM with regard to 4 meg jumpers etc.  Best as I can recall the failure to work with the static ram, came at a point

where I was moving boards around from one machine to another.  I have checked to jumper settings as shown on this group.  Again no

mention of TMA0 or PHANTOM.   I bring this up because the static ram has those inputs connected to the address decode circuit.  I 

may not have pullups on those lines.    I can look into this tomorrow.

JC

[Jay Cotton]

In a fit of desperation I shut out the Phantom * signal and put in a ton of wait states.

And....  Booted UNIX on my XMU/MMU.  Very relieved to have this working again. 

I am seeing some memory faults that are causing core dumps, so I guess that

I have to much wait state set up.

Thanks to everyone for your help

JC

[Mike Stein]

Glad to hear you're making progress!

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