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Author Topic: What is the System Bus Bridge (Read 5354 times)

Offline OA128

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What is the System Bus Bridge
« on: 2007.March.05. 14:22:40 »
again me ;)

I found a "System Bus Bridge" for EP128. What is its use ?

Bye !

Offline gafz

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Re: What is the System Bus Bridge
« Reply #1 on: 2007.March.05. 14:33:21 »
again me ;)

I found a "System Bus Bridge" for EP128. What is its use ?

Bye !

It's a connecting module between the machine and extensions (EXDOS floppy disc controller, hardware Spectrum Emulator).
« Last Edit: 2007.March.05. 14:35:43 by gafz »
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Offline Zozosoft

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Re: What is the System Bus Bridge
« Reply #2 on: 2007.March.05. 14:51:51 »
Schametic of the Bridge.
This generate +5V power suply for the extension card, can work from the 9V output from the machine, or other external power supply.
And added 3 address select pins. This is for "plug and play" :-) The connected card can decode standalone I/O port and memory addresses by these pins. But we never see officialy released multi sockets bus extender unit. And only one official card released, the EXDOS. Only this card use this address decoding method.

In Hungary is exist a unofficial Bus Extender unit, but this and other unofficial cards not use the original address decoding idea :-(

Offline OA128

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Re: What is the System Bus Bridge
« Reply #3 on: 2007.March.05. 15:06:53 »
Thanks for your answers !

"It's a connecting module between the machine and extensions (EXDOS floppy disc controller, hardware Spectrum Emulator)."

If this module is always necessary, why didn't they include it into the computer ?

Offline gafz

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Re: What is the System Bus Bridge
« Reply #4 on: 2007.March.05. 15:31:20 »
If this module is always necessary, why didn't they include it into the computer ?

Price of the machine was lower... :) (Sorry, i don't speak english. :oops: )
« Last Edit: 2007.March.05. 15:32:55 by gafz »
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Offline Zozosoft

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Re: What is the System Bus Bridge
« Reply #5 on: 2007.March.05. 15:49:38 »
If this module is always necessary, why didn't they include it into the computer ?
Good question :-)
But all unofficial EXDOS cards in Hungary come with direct connector to machine.

I think the original developers thinked about the following things:
-not overload the machine power supply and the internal power circuits
-the address decoding mechanism (this is very good idea, but unfortunately not released more official cards, and multi slots bus extender)