Wirin' up blinkenlights

From: allisonp <allisonp_at_world.std.com>
Date: Thu Jun 8 20:51:52 2000

>Interesting idea, a Q-bus front panel.
>The address lines are present, just wire those up to lights. Various

Nope! they are address/data multiplexed... you have to latch the address
and data to display it.

>signals are there as well. A DMA cycle can take forever so you could build

nope, it will bus timout on you.

>the switch register to deposit directly into memory. Decoding an address
>for the switch register in the top 4K would be pretty straightforward as

Yes it would.

>well. Does anyone know if there is a defined location for it? Displaying
>registers would be difficult to do "on the fly" however you could probably
>force the CPU to execute a MOV Rx, #DISPLY fairly easily.

Software loop on an interrupt would write to static latches to do that.

>Circuit Cellar Ink on building your own CPU in an FPGA (see
>www.fpgacpu.org) and it included a VGA interface (which they displayed
>characters on) clearly however if you were using it as God intended you
>would create a virtual front panel :-)

interesting. The reason for frontpannels in the first place was more
diagnostic in nature and to start them up. When ram and rom got cheaper
along with mass storage the whole point of the frontpannel becomes
passe`. My 8f would be hard to use without it as it has no rom and
it's a maintenance tool. From the other side, it would be pointless on the
11/73 as the rom monitor is much more useful than any front pannel.
The ALTAIR was the machine that made having a frontpannel when
rom would do clear for me. It was a lot of hardware to do what a
simple rom card could do better.

Received on Thu Jun 08 2000 - 20:51:52 BST

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