🚀 go-pugleaf

Peter E. Fry wrote:
> 
> Videoman wrote:
> > Like everything else in the PC's "design", it's a bit screwed up.
> > Technically, the PC could support 64 IRQs using the same PIC chip that
> > it does now. The problem is, where do you put the IRQ lines on the bus
> > connectors? That's a lot of pins.
> 
>   64 (or even 63) IRQs with two 8259s?  How?  And with level triggering

Sorry, I should have said "same PIC chip model". Their architecture
allows them to be configured with up to one master and 8 slave PICs.
(Not sure if you can then expand to 64 chips, etc, probably not.)

> available, why?  Edge triggered interrupts was a cost-related decision
> on the original PC, and a mistake, as it turns out.  But as far as I
> know the 8259 has eight channels, period.

Per chip, yes. But you can cascade them. (As a side issue, why the heck
do spurious ints get reported on the highest IRQ line for that PIC? It
really doesn't serve any use that I can see.) You're right about
edge-triggered being a mistake.

> > The future is not hardwired IRQ lines, but a network of connected nodes
> > for each device. USB is like this, and certainly more to follow.
> 
>   I imagine you may be right, there, but I'll bet PCI lasts for a while.
> Seems the only way to get superior throughput over reasonable distances
> with reasonably low RF emissions is fiber optics.  USB, while superior
> to RS232, does not have near the performance to act as a system bus.

You got it. I was actually thinking about a universal all-digital
fiber-optic connection scheme before USB was announced. Think about all
the devices in the PC that simply convert from one interface to another.
Modem? Disk controller? Serial ports? Parallel ports? Ethernet? All of
these, and more, could be connected via a universal fiber-optic link.
Conceivably, the same link would also be used for local-area and
wide-area telecommunications. We could have various storage, CPU, and
I/O nodes attached to this monstrous global network. Need more power for
that new hyper-VR game? Easy, just add a couple more CPU nodes, or
borrow your friends nodes from across the street.

The USB standard seems to leave a lot to be desired. As usual, right
idea/concept, wrong design/implementation. Computer companies really
need more visionary designers (hey, hire me). Imagine if computers were
as well designed as, say, the Amiga, _and_ as well marketed as the PC.
Sigh. I guess we can dream, right?