[Info-vax] OT: news from the trenches (re: Solaris)

[glen herrmannsfeldt]

seasoned_geek <roland at logikalsolutions.com> wrote:

(snip, I wrote)
>> The AT/370 maps into host memory at 512K to 640K. The XT/370 takes
>> even more host memory space.  Yes terminal, printer, and disks, but 
>> much of the processing that is done is S/370 code in real VM/370
>> is done in 8088 code for VM/PC.  Some years ago, there was a company
>> selling board sets for a low price, about $30 each. 
 
> http://www.techadvice.com/tech/M/mem-adr.htm
 
> Do you mean A000-FFFF? Also known as the dastardly 128. 
> In theory all for the video card, but low end video cards 
> used only a tiny portion so _everybody_ provided cards with 
> jumpers and/or dip switches to change the settings so people 
> could wedge the card in.

No, X'80000' to X'9FFFF' 

The XT/370 uses X'40000' to X'9FFFF'.

It is dual port and bank-switched on the ISA side. 
Both boards have 512K on board. 

They do virtual addressing with a look-up table that gives the real
address for every page of 4M virtual address, so nothing like the
real S/370 virtual addressing, but much easier to implement.

I (still) have an Everex AT clone from about 1987 that has switches
to allow for 512K on board and the rest in ISA slots. 
I also have the memory board for extended (above 1M) memory.

I once wondered about 386SX boards, which would be faster, but not
many of them had/have the ability to do addressing that way.

(snip)

-- glen