Modern external storage emulating RX02 (was Re: Most used toys, was Re: The late, great TRS-80)

[Allison]

>
>Subject: Modern external storage emulating RX02 (was Re: Most used toys,was Re: The late, great TRS-80)
>   From: "Ethan Dicks" <ethan.dicks at gmail.com>
>   Date: Wed, 27 Jun 2007 11:14:19 -0400
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On 6/26/07, Dave McGuire <mcguire at neurotica.com> wrote:
>> > Serially connecting would rot though...
>>
>>    Yeah, kinda.
>
>I was just reading some old list threads about PDP-8s and TU58s and
>emulators - transfer speed aside, the real problem was that most
>pre-OMNIBUS PDP-8s didn't have a spare serial port (just the console
>TTY), and that the serial hardware needs to be able to send a Break to
>the TU-58 to properly initialize and reset the controller in the
>TU-58, and unmodified PDP-8 hardware can't do that.  I did run across
>a bunch of old 12-bit SIG newsletters from when the TU-58 was new, and
>all the gyrations folks went through to be able to use them, since at
>the time, they were about the cheapest mass storage you could get from
>DEC.  One entire aspect of the project was how to mod M706/M707 or
>KL8E serial interfaces to generate a break.  Another aspect was trying
>to wedge a driver into a couple of pages of code.

Using a Tu58 on an -8 is not a goot match and there are lots of gyrations.

>
>If all PDP-8s had a spare serial port, it might make sense to have a
>serially-attached modern mass storage peripheral.

Adding a second serial is trivial as there were many differnt serial 
cards available.  To make a TTY card RS232/432 passable is also not hard.


>  Since that's
>nowhere near universal, it frequently comes down to deciding on which
>models to support.  One of the few disadvantages of the PDP-8 spanning
>1965 to 1994 (PDP-8 to DECmate III) is that there's a huge variety of
>hardware that all runs the same instruction set (give or take a couple
>instructions), but with an equally huge variety of default peripherals
>and expansion options.   An RX01/RX02-attached device, at least, will
>work with OMNIBUS machines as well as the VT78 and DECmate I - overall
>not a bad range to cover.
>
>-ethan

What is possible now is a small micro and a big static ram of 512k are 
which fairly easy to find it's not unreasonable to simulate a RX02
using a micro at the end of a serial line (or parallel) and NOT use 
the protocal of TU58. The cpu/micro used does not have to be very high 
powered or fast as all it's doing is data transfer and PDP-8 PIO is 
usually slower than 30-40K words/sec.

In the end what is used is more a matter of convenince than technology.

I happen to be lucky(?) as my 8f has two serial cards but nothing 
else device wise. One of th cards is the usual console TTY but the 
other is a UART based M8652 that were often used for modem 
banks and serial data concentrators/switches made using PDP-8s.


Allison