Data Systems Design DSD-880 8" floppy and hard drive?

From: rogersda_at_cox.net <(rogersda_at_cox.net)>
Date: Wed Jul 23 00:39:00 2003

Jerome Fine <jhfinexgs2_at_compsys.to> wrote:

> I agree there needs to be a SYSGEN to be able to use
> all 3 * RL02 drives with the DL(X).SYS device drivers
> and the hardware handles ONLY 18 bit addresses for
> both the DYX.SYS and DLX.SYS device drivers.
>
> BUT the RLV11 and the RXV12 from DEC also
> managed to handle only 18-bit addresses. So the
> DSD box was completely compatible with the stock
> (distributed) V4.00 of RT-11.
>
> However, V4.00 code in DY.MAC contained the
> extra instructions to use a double-sided media which
> would probably have been called an RX03. And
> although those extra instructions had bugs (after all
> they had never been tested) and were removed by
> V5.00 of RT-11, I did fix the bugs and ran a DYX.SYS
> device driver under V5.03 of RT-11 using the DSD
> 8" floppy as a double-sided drive. In addition,
> I also added a bounce buffer in DYX.SYS so that
> a user buffer above 256 KBytes could be used
> with the 18-bit hardware addresses in the floppy.

   Actually, for device I/O, it doesn't matter whether
one is using 16, 18, or 22 bit addressing. The PDP-11
I/O page is defined as from 28KW-32KW, which is entirely
within the range of 16bit addressing.

Dale Rogers
DEC/Compaq/HP
Received on Wed Jul 23 2003 - 00:39:00 BST