1. There's more than one alternative. Look at STAR-100, with
256 addressable registers, or the older Atlas with 128.
2. "No one would ever want to run more than 15 jobs at a time"
would have been dubious even in 1965.
3. The overhead for block relocation is miniscule.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
________________________________________
From: IBM Mainframe Assembler List <[email protected]> on behalf
of Paul Gilmartin <[email protected]>
Sent: Tuesday, December 5, 2017 6:37 PM
To: [email protected]
Subject: Re: Access registers
On 2017-12-05, at 14:34:01, Seymour J Metz wrote:
> The combination of a 4-bit register field and using the same registers for
> accumulators,
> base registers and index registers.
>
The alternative leads to LR pollution.
> 4 bit storage protect keys
>
No one would ever want to run more than 15 jobs at a time. If someone
does nowadays, the correct approach is segment protection.
> No address translation. Maybe paging was too expensive, but surely block
> relocation
> was doable.
>
I believe the perceived cost wasn't paging (you don't need to page
if you have enough real memory), but DAT overhead.
> ______________________________________
> From: Charles Mills
> Sent: Monday, December 4, 2017 5:55 PM
>
> I believe someone (Harlan Mills? Fred Brooks?) said that he felt the only (or
> most significant?) *error* in the System 360 design was the 24- rather than
> 31- or 32-bit addressing.
>
> Anyone who has wrestled with legacy control blocks in the modern era would
> probably agree.
-- gil
