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From: apratt@atari.UUCP (Allan Pratt)
Newsgroups: comp.sys.atari.st
Subject: Re: TT REVIEW
Message-ID: <2884@atari.UUCP>
Date: 27 Mar 91 01:38:39 GMT
References: <1991Mar20.141344.6808@newcastle.ac.uk> <1565@aupair.cs.athabascau.ca>
Organization: Atari Corp., Sunnyvale CA
Lines: 47

>D.B.Barratt@newcastle.ac.uk (Dave Barratt) writes:
>>The following is more or less the complete  review of the TT by 
>>Richard Monteiro, which appeared in the April edition of Computer 
>>Shopper (UK edition). (Article 359 lines in total)

rwa@cs.athabascau.ca (Ross Alexander) writes:
>I think that's a 256-byte rather than a 256 Kbyte D-cache [...]

Right.

>About the serial ports: how many _uarts_ does this machine have, as
>opposed to how many connectors appear on the back?

Here's the deal.  There is a 68901, just like the ST, and that goes to the
"Modem 1" connector on the back.  It has all the signals that the ST has,
in all the same places.  It's your primary compatibility-mode port.

There's a 8530, which contains two channels.  One of those channels,
Channel A, goes to EITHER the LAN connector on the side OR the port labeled
"Serial 2" on the back.  It's got all of the modem control signals, except
Ring Indicator.  ("All" is TX, RX, CD, DTR, DSR, RTS, CTS, RI, and ground
("earth" to you Brits :-).) You select which connector Channel A actually
goes to in software.  You can't use both the LAN port and "Serial 2" at the
same time.  

Channel B of the 8530 goes to the port on the back called "Modem 2." It has
all the modem control signals, including RI.

Finally, there is a second 68901 MFP, and its serial port appears on the
back of the TT as "Serial 1."  It is a three-wire connection: transmit,
receive, and ground only.

In case you couldn't tell, the two "modem" connections have all the
signals, and the two "serial" connections don't: "Serial 1" has only three
wires, but "Serial 2" only lacks RI.

If you have a VME card, you lose the Serial 1 and Serial 2 connectors,
unless you mess with your case (and probably void your warranty): the
connectors appear in the (otherwise empty) VME slot.

As for "checklist engineering," we did it this way because the serial port
is free if you're not using the LAN connector: if you don't use the LAN
port, would you rather have that serial port, or nothing?

============================================
Opinions expressed above do not necessarily	-- Allan Pratt, Atari Corp.
reflect those of Atari Corp. or anyone else.	  ...ames!atari!apratt