Heathkit H27 - test-drb@ccmp.vtda.org

6 Sep 2006

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Subject: Re: Heathkit H27
   From: "Ethan Dicks" <ethan.dicks at gmail.com>
   Date: Thu, 07 Sep 2006 12:30:11 +1200
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

On 9/7/06, Jay West <jwest at classiccmp.org> wrote:
  Can the H27 (dual 8" floppy drive) be hooked
up to an H8? Or was that
 strictly an H11-only device? 
Dunno about the H8.

> Of for that matter, can an H27 be hooked up to a non-heath Micro PDP11? 
Yes, if you have the heath interface card as well.  If memory serves 
the standard RT-11 DX.sys was compatable.

...

My recollection of debugging some H27 issues a couple of years back is
that there's a boot prom on the Qbus card for the H27.  If that's the
case, then as long as it isn't stomping on a bootstrap ROM somewhere
else on the bus, then you should have no problems.  Heath's card should
be register-level compatible with either the RXV11 or the RXV21 (can't
remember which one right now). 
The prom on card can be disabled.  It worked well with 11/2 and KDF-11A 
cpus.

The card is RXV-11 compatable.   The big upside with the H27 is it would 
format 8" (RX01) disks.  The downside is the drives, the spindle clamp
was plastic and would dryout and crack.

...
 My H-11 came with a KDF-11, DEC memory, pretty much
DEC
everything; just the Heath backplane and PSU and floppy controller.
The previous owner never booted from floppy, though; he hacked the
case and added an off-to-the-side CD-interconnect and used an RLV11. 
Thats a ugly hack.  Many were upgraded to 11/23 cpu, Q18 ram and some
times DLV11j for more IO with fewer boards.

...
 It took a bit of work to get it all back together.

I'll bet.  Test the PS well, the LVSMPS was not every reliable.

Allison