Subject: Re: what's this machine check mean?
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
From: Wilko Bulte <>
List: port-alpha
Date: 04/16/2000 02:31:45
On Sat, Apr 15, 2000 at 02:54:25PM -0400, der Mouse wrote:

> > These 30->72 pin converters will most likely overload (much more
> > chips!) the memory bus of the machine.
> I actually have four adapters, two each of two sorts.
> One sort is completely passive - pc board and 30-pin sockets, nothing
> more than that.
> The other sort has five small chips surface-mounted on it.  Four of
> them are marked "F04" and "XAE530", with a Motorola logo.  The fifth

Probably a 74F04 hex inverter (F-TTL logic)

> says, on one adapter, "F08" and "XAA512" (also with the Motorola logo);

Probably a 74F08 (and or or gates or something like that).

> on the other, "F08" and "ZAY510" (and the logo).  There are also eleven
> surface-mount two-terminal devices.  Seven of them are marked C1
> through C7 and are presumably power-supply deglitching capacitors (five

Yep, power decoupling sounds logical.

> are solder pads marked R3 and R4 but no resistors on them.)  The
> surface-mount ICs are 14-pin and hence have pin count enough to be
> address buffers (data buffers are, of course, unnecessary).  Using the

Databuffers are not unecessary, RAM chips give substantial capacitive
loading! You have 4x the number of RAM chips compared to typical
72pin SIMMs.

> SIMM socket pinout in the manual whose name I deleted above, I can
> trace many of the etch runs on the adapter, and it certainly looks as
> though the surface-mount chips are address buffers.

Or address decoding.

> The bad news is, it didn't work: even after waiting a full minute, I
> got nothing out the console serial port.  (It normally starts printing
> stuff about 45 seconds after power-up.  I don't have the diagnostic
> LEDs hooked up.)

Hm, I still would check what ordinary 72 pin chips do.

> The good news is, it apparently didn't fry anything; when I switch back
> to the 80ns SIMMs, it works as well as it ever did - that is to say, it
> boots and runs for a little while, then machine-checks reporting a pc
> in lca_mem_read_1.

If worst come to worst I can maybe find you a 21066/166Mc chip. Will have to
do some digging.

Wilko Bulte 		Powered by FreeBSD