mike@LOGICON.ARPA (07/06/84)
A person here at Logicon has a question concerning the IBM PC/XT system
and needs some help. And here is his question....
I am in the process of building up a PC/XT system "from scratch" -
I have purchased an XT motherboard, chassis, and power supply as service
parts, and am accumulating the rest of the parts to make a working system.
Does anyone have firsthand information about third-party hard disk sub-
systems that can work with the XT motherboard? The XT motherboard evidently
(it's still on order) does NOT have an empty ROM socket into which an
additional ROM containing hard disk BIOS stuff can be plugged. Most third-
party hard disk controllers (I am told) use a ROM that plugs into just such
an empty socket on the PC motherboard. The IBM approach, on the other hand,
is to physically locate the ROM on the hard disk controller board, so an empty
socket on the XT motherboard is - for them - unnecessary. Can anyone tell me
of a third-party hard disk subsystem with the ROM on the controller card?
Please address all comments back to me and I will see that the response
is directed to the correct individual.
Thanks...
Mike Parker
{alias mike@LOGICON.ARPA}COLE@USC-ISIB.ARPA (07/07/84)
From: Randy Cole <COLE@USC-ISIB.ARPA> I think you have been misled about the location of the boot ROM for hard disk controllers. I have a Kamerman Labs system, which uses a Data Technology Corp. (DTC) controller. The ROM is located on the controller board. I am sure the Western Digital controller also has the ROM on board. What happens is that during the boot process, newer PCs (the so-called PC2s, which use 64K RAMs on their motherboard) and XTs look for adapter cards with program ROM, starting at C8000 hex and looking at 2K increments through F4000 hex. The code in the ROMs must start with a hex 55, then a hex AA, and then obey a few other rules. If the PC or XT finds such ROM code it will do a jump far to byte 3 of the ROM, allowing the controller or whatever to hook itself into the system. The DTC controller is a DTC-5150 BX. Western Digitals is a WD1002-WX2 (I think). They both cost $295 and the Western Digital can be bought from Kierulff in the LA area. Randy Cole -------