Subject: Re: what's this machine check mean?
To: None <>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
List: port-alpha
Date: 04/17/2000 21:55:51
> Sadly, should your axppci33 actually work "perfectly", it's lack of
> speed will be so pronounced that the distinction between "perfect"
> and "broken" will be meaningless.

I think you've been spoiled by high-end machines.  My fastest home
machine at present is a 486DLC/33; the fastest of them which I can
count on for a "make build" without falling over is a SPARCstation IPX
(supposedly 40MHz, for what that's worth).

A 166MHz alpha, even without cache, will be a distinct step up for me.

> Those come with and without cache, BTW.

Mine has no cache, but does have sockets I could put cache in.

> Now, having discouraged you from even caring, if you do want to try a
> really deep hack you might be able to make a marginal kernel reliable
> with a custom set of bank timing registers.  The LCA has an
> integrated DRAM controller, see page 5-20 in ec-qc4ga-te,

I'm fetching it now.  I suspect this isn't it, though - see below.

> It's not a true fix, because (1) the SRM settings have to work well
> enough to get the kernel loaded

This has not proved to be a problem.  The only time I saw machine
checks before the kernel booted was when I had some otherwise untried
memory in there (not sure it was even as fast as 80ns).

> and (2) those registers are write-only (!@#!) so you don't get to
> tweak them, you can only just load really conservative values in.

(Eww.)  I'll keep it in mind...and whether I had it or not, I haven't
read ec-qc4ga-te.  I'm flipping through it now.

[re power supplies and grounding]
> 	* Don't worry about your setup too much .. the board is a world
> 	  unto itself, and doesn't really care where ground is until
> 	  you start connecting it to other things, which generally
> 	  supply a good ground or, like serial I/O, are somewhat
> 	  tolerant of bad ones.

That's more or less what I figured.  I've set up the system with
exactly four things connected off-board: (1) the power supply; (2) the
console serial line; (3) the (SCSI) disk, which is powered off the same
power supply as the motherboard; and (4) a twisted-pair Ethernet card
in one of the PCI slots.

As I remarked, there is no case to ground it to, so I haven't worried
too much about it.

[Wilko, on speed]
> NoName boards were sold in the Netherlands last November
> new-in-the-box for US$ 12 each.  At such a price one cannot complain
> about price-performance ratios.

Mine was US$ 12 less than that.  I'm not complaining. :-)

>> Those come with and without cache, BTW.  I'm not sure what the speed
>> contribution of the cache is, although it feels funny to even use
>> the word "speed" when referring to an LCA box. :-)
> Without cache life becomes rather miserable.

If I can make these bloody machine checks go away, I'll probably get
some cache to go in it.

Today I picked up five 4M sticks of 70ns-rated RAM and have tried the
machine with them.

It's no worse, but it's also no better.  I'm seeing exactly two
predictable aspects of these machine checks:

	- They always show a pc in lca_mem_read_1

	- They always occur approximately the same amount of time after
	   power-up, this time delay getting smaller with later

In view of the latter, I suspect thermal problems - especially since
the 3.3V regulator heatsink gets hot enough to concern me.  I'm
pondering ways to cool things more effectively.

					der Mouse

		     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B