Hey, English blokes...what's an Apricot?

From: Hans Franke <franke_at_sbs.de>
Date: Tue Jul 7 13:06:19 1998

> [8089]
>>> (very fancy DMA chip).

>> Thats like naming the Newton a fancy post it thing. The
>> 8089 was a full featured CPU, just with an special
>> command set suited for I/O operations. Anything from

> True. I've got the 8089 data sheet, and a 3rd party '8089 I/O processor
> handbook', and it is indeed a coprocessor. However, it's normally used
> (and it's used in the Apricot) as a DMA controller, so it's best to think
> of it that way, for all it can do a lot more.

> It's a lot nicer than the 8237 used in the IBM PC. For one thing it
> correctly handles the 20 bit address bus, so there's no problem with
> crossing 64K boundaries. For another, it can monitor a Data Ready flag on
> one port, and transfew data when the peripheral is ready. No need to have
> DMA channels in the PC sense.

>> serial I/O via disk I/O up to code translations could
>> done in a very smooth and genuine way.

> Howver the Apricot has a normal serial chip and disk controller, and only
> uses the 8089 for DMA.

Maybe I used the wrong words - poor english language skill -
Of course a regular Serial I/O chip is still needed, the
8089 has no serial (or what ever) I/O of its own. But instead
of the main CPU, the 8089 will respond to all requests
for data transfer - shure, you could use two DMA chanals
for input/output data, but in difference to an ordinary DMA
the 8089 could also handle the status lines and drive a non
hardware protocoll - from xon/xoff up to HDLC. Same for any
other kind of I/O hardware, not only serial, since the logic
is software not hardware.


Ich denke, also bin ich, also gut
Received on Tue Jul 07 1998 - 13:06:19 BST

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