[HECnet] VAX-11/725 with RC25 (was: Re: Reading RT11 files under Windows or Linux)

[Paul Koning]

> On Apr 21, 2021, at 4:25 PM, Dave McGuire <mcguire at neurotica.com> wrote:
> 
> On 4/21/21 4:05 PM, Mark J. Blair wrote:
>>>>> Anyone have an RC25 unit?  I have a few of them in need of imaging up before they are lost forever...
>>>> 
>>>> I do not have one yet, but I would be interested in buying a VAX-11/725 if one came along at the right price and location. I'm in Riverside, California, USA. I keep hearing so much ire directed towards the RC25, that I have a sick fascination with experiencing one for myself, and seeing just how much slower it feels vs. my 11/730.
>>> 
>>> The VAX itself won't feel any slower; it's the same board set as the
>>> 11/730.
>> 
>> For CPU-heavy stuff, but isn't the RC25 subsystem a lot slower than the RL02+R80 subsystem? See, I need a VAX-11/725 so I can be an expert on this stuff! :)
> 
>  Excellent acquisition rationalization. ;)  But yeah, the RC25 is
> noticeably slower than the (already pretty slow) IDC controller that
> handles the R80 and RL02 in an 11/730.  (I had an 11/725+RC25 many years
> ago, and a standard-config 11/730)  I was just thinking CPU differences,
> of which there are none.  Context fail. ;)
> 
>            -Dave

Is that specific to the RC25 controller used on that machine?  On PDP11s, RC25 is an MSCP device, and I don't remember ever hearing it was particularly slow.  Of course, it was a pain in the neck with its fixed drive section, but that's a different issue.

I remember when we got a fairly substantial order from the Royal Navy for RC25 based RSTS systems (with the fixed part as the boot drive, which requires some OS hackery to allow the OS to survive having that spin down when you need to swap the removable cartridge).  Rumor had it that those systems were going into submarines, so they needed to be small, which the RC25 delivered.  Not sure if that's accurate.

	paul