RC25 (was Re: Modifying microcode)

[Ethan Dicks]

On Mon, Jun 4, 2018 at 5:13 PM, Paul Koning via cctalk
<cctalk at classiccmp.org> wrote:
>> On Jun 4, 2018, at 1:17 PM, Robert Armstrong via cctalk <cctalk at classiccmp.org> wrote:
>>
>> ... FWIW, I have a 725 complete and working.  Well, except for the RC25, which never worked even when they were new.

I had an 11/725 in the 80s and 90s and never had a problem with the
RC25 but they are legendarily terrible.

> Hm.  I remember some RC25s on RSTS, and they seemed to be ok.  The fact that they had two drives on one motor made it strange, especially if the fixed platter was your system device.  We had to teach the OS how to deal with SY: going away temporarily.

Oof, yeah.  When I used my 725, I didn't spin the RC25 up and down
except when booting and shutting down.  I also had devices like RL02s
for removable storage.

I often wonder how hard it would be to develop some other storage
device for the KELSI but then other projects push to the top of the
stack and I move on.

Mostly, what I need is affordable ($250 or less) Unibus storage with
modern media (Flash or IDE adapter or whatever).  I don't really care
what form it takes but Unibus SCSI cards are quite pricey and making a
new controller is even less affordable (I used to make and support
DMA-enabled Unibus communication controllers for a living so I have a
pretty good idea of the amount of effort required).

-ethan