[HECnet] A2RTR downtime

[Peter Lothberg]

Fotnode, MRC gave me the BBN pager from Sails KA, and I later gave it to LCM, together with 3 KA's and the BBN pager and the boards for the KA to 
connect to the pager. In the late 80's we also did build a ITS-pager for the KA. 

One of the KA's we brought up 6.03A on in 2019. Ralph Gorin pushed the "read-in" button for that event. 

The SC30/SC40 can do "KI-Style" Tops10 10 pager and "KL-Style" Tops 20 paging. The Toad is 'special' it has a lot of the KC10 fetures and don't do any "KI style" things 
and has 32MW of memory. 

-P 

> From: "tommytimesharing" <tommytimesharing at gmail.com>
> To: "hecnet" <hecnet at Update.UU.SE>
> Sent: Tuesday, October 19, 2021 6:53:31 PM
> Subject: Re: [HECnet] A2RTR downtime

> I understand your point here and you are--of course--correct, yet one hesitates
> to term Tops-20 (TWENEX ) paging as being a variant of the BBN pager (or better
> TENEX).
> The BBN pager was far more capable then the both the KI and KL pagers. The KL
> pager was more capable than the KI, but this didn't put it quite in the same
> league as the BBN pager in terms of functionality.

> This is most visible in what RPACS% (Read PAge ACess) returns (or fails to
> return) and what SPACS% (Set PAge ACess) does (or fails to do). On the KL, the
> only access bit you can set is whether the page is writable (this includes
> Copy-On-Write). You cannot:

>     1. Clear all bits and thus set a page 'No Access'; it will still be there
>     2. Set a page Write-only
>     3. Set a page Execute-Only

> Case 1. is necessary for implementing guard pages which are (IMHO) one of the
> very most effective hardware based debugging tools around. You really want
> "Explode on Reference" to catch stray reads AND stores. If you whack the page,
> then all that happens the next time you touch it is it 're-materializes'.

> Case 2 is great for increasing the security of certain communications paradigms.

> For 1., you can solve it in two convoluted ways. First, you can hook the page
> creation interrupt and determine whether you are creating something you ought
> not. You can also actually implement "Explode on Reference" by mapping 1+ the
> last page of a locked file. If you then try to touch that page, it will fail
> because creating the page in memory involves creating it in the (locked)
> backing store. I discovered this by mistake when looking for a guard page
> implementation for my FTP server.

> 2. Has no real solution, but paged mode IPCF% is probably good enough.

> 3. is partly solved by setting the file execute only, but this is highly
> restricted and does not work if a program is multi-process (I.E., forks). Thus,
> I can not use it in the FTP server nor can it be used in the Tops-20 TELNET
> client.

> BBN repeatedly tried to get DEC to take their pager, but DEC never went for it.
> I don't remember what was designed for the Jupiter or was implemented for the
> SC-40 or TOAD.

>> On 10/18/21 10:03 PM, Robert Armstrong wrote:
>>> T10 in the last incarnation(s) could use the KL10 paging

>> Umm.. TOPS-10 could always use the "KL10 paging". TOPS10 ran on the KL from day
>> 1. The thing is, the KL had different microcode for TOPS-10 paging and TOPS-20
>> paging. The hardware didn't change. TOPS-10 paging was the same as the KL10
>> paging, which was implemented in hardware. TOPS-20 paging (or rather, TWENEX
>> paging) was some variant of the BBN pager that was originally attached to a
>> KA10 way back when. Bob
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