DEC 3000 (alpha) faultfinding

[Douglas Taylor]

I have a functioning Alpha 3000 300, perhaps it can help with some of 
the questions you have.
Doug

On 3/28/2018 4:17 PM, Peter Coghlan via cctalk wrote:
> I've got a DEC 3000 model 300 and a couple of DEC 3000 model 600 alphas which
> failed some time ago and the recent Alphaservers thread has rekindled my
> interest in getting them working again.
>
> A couple of years ago, there was another thread "AlphaStation 200 NVRAM Problem"
> where the Alpha SROM mini console and various items of useful documentation
> were mentioned.  I have now made up an adapter (cable and MAX232 line driver /
> receiver) as described in that thread to allow me to to talk to the the SROM
> mini console in my alphas and I am please to find they are all responsive at
> this level.  I also found: "DEC 3000 300/400/500/600/700/800/900 AXP Models
> System Programmer's Manual Order Number: EK-D3SYS-PM. B01" (d3syspmb.pdf)
> which describes some of the internals of the machines in question.
>
> The mini console commands available on the model 300 are very limited compared
> to those in the documentation which targets a much later machine.  However, it
> does have mt (memory test) which is not present on the model 600 for some
> reason.  Results from this suggests that all 6 SIMMs present are bad in pretty
> much all locations. This seems a bit unlikely to me.  Perhaps there is a
> failure in logic which causes the memory not to be accessed at all?
> Unfortunately, the manual does not seem to give any leads on how to diagnose
> this further.
>
> The em (examine memory) and dm (deposit memory) commands only accept 32 bit
> addresses meaning they cannot to be used to access input/output areas which
> require at least 33 bit addresses.  However, a little experimentation led me
> to the existance of ei and di commands which can do this on the DEC 3000
> machines and I found I can use di to update the diagnostic LEDs on the machines.
>
> The DEC 3000 600 machines both (usually) count down to F0 on their diagnostic
> LEDs and hang without producting any output on the main console.  They do
> however produce output on the mini console - for example:
>
> DEC 3000 - M600 SROM 6.1
> Powerup Sequence
> ff.fd.fb.fa.f9.f8.f7.f6.f5.f4.f3.f2.f1.f0.
> sysROM  00000033.000006f1
> ioROM   00000033.00000162
> MCRstat 11111111.808011c0
> bnkSize 00000300.00000c01
> memSize 000000c0.000000c0
>
> However, they do not provide the SROM> prompt or accept mini console commands
> unless a I engineer another fault condition such as by pulling out one of the
> memory risers.  I wonder if there is a jumper to enable mini console commands
> to be accepted without doing this? Looking around the system board, I see a
> pair of jumper pins labelled J9 hidden under the I/O board which looks like it
> could do this.  Unfortunately, while there is legend on the PCB indicating the
> function of all other jumpers, there is none for J9 and it is not mentioned in
> the manual either.
>
> On the I/O board, there is one three pin jumper labelled simply "Off" and "On"
> and it is jumpered to the "On" side.  It is close to the SCSI connector so I
> suspect it is more likely to be something to do with termination or termpwr
> than the mini console.
>
> One of the model 600s sometimes generates a machine check, like this:
>
> DEC 3000 - M600 SROM 6.1
> Powerup Sequence
> ff.fd.fb.fa.f9.20.
> MCHK
> exc_addr        00000000.00001484
> biu_stat        00000000.000022d8
> dc_stat         00000000.00000007
> fill_adr        00000001.f0080050
> fill_syn        00000000.00000000
> DataExp aaaaaaaa.aaaaaaaa
> DataRec aaaaaaaa.aaaaaaaa
> MCRstat 11111111.808011c0
> bnkSize 00000300.00000c01
> memSize 000000c0.000000c0
>
>
> SROM>
>
> While this can be useful because it gets me to the SROM> prompt, I can't
> find anything in the manual which helps me diagnose what might be causing
> this.  The meaning of the contents of biu_stat might be a useful start.
>
> The 600 machines have a socketed 27C512 EPROM.  I assume this must be the SROM
> (although I can't see what is serial about it) as the machines fail to update
> the diagnostic LEDs or write to the mini console if it is removed.  I dumped
> the two EPROMs and compared them and they are identical.  However, I can't see
> any ASCII strings in them.  Perhaps the bits are not used in the standard
> order?  The manual suggests that there are 8 different 8KB SROM images present
> and those other than the "standard" one may be used for testing and diagnostics
> by setting jumpers. Unfortunatly, there is no further information about these
> images.
>
> The manual hints that the System ROM (SYSROM) (actually an FEPROM) is located
> at 1 E000 0000 to 1 E003 FFFF, however, looking at the beginning of this area
> with ei suggests it is in fact the IOROM (also an FEPROM).  Hunting around
> some more, it seems that setting bit 9 of the System Support Register at
> 1 E004 0100 brings in the SYSROM instead (although the manual suggests bit 7
> is also involved which seems unlikely as this bit is one of the diagnostic
> LEDs).
>
> The format of the headers in the SYSROM and IOROM do not exactly match the
> format given in the manual but they are "close".  I wonder if this might
> be my problem or if the manual is incorrect.  If anyone else has a 3000 600,
> could they take a peek at their SYSROM and maybe we could compare notes?
> It may be possible to map the SYSROM from a running operating system but as
> none of my 3000 machines run right now, I am not in a position to try this
> myself.
>
> Regards,
> Peter Coghlan.