Jerome Fine replies: I am not sure just where to add the information about a VT103. I suspect that the backplane in use is the 2 * 4 (H9281-AB) or a 4 * 4 (H9270). Along with a few other bits of hardware, including a fan and a better power supply, a VT103 is almost identical to the VT100 upon which the VT103 is based. And since the location in a VT103 where the backplane is located is empty in a VT100, it is possible to say that a VT103 is the same physical size as a VT100. It is even possible to place a hard disk drive under the tube (there is sufficient room for a full height 5 1/4" hard disk drive, let alone a SCSI 3 1/2" hard disk drive), but placing a hard disk drive there is certainly not a DEC solution. Back in the 1980s, DSD (Data System Design) sold many VT103 systems with a DSD 880/30 combination which emulated 3 * RL02 disk drive and single RX02 floppy drive. The controller interface was a single dual Qbus board which contained boot ROMs as well. Normally an M8186-AA (dual 11/23) was used, but an M8192-AA (dual 11/73) was also possible. Since the original backplane was only 18 bits, only 256 KBytes could be used. But after the backplane was enhanced to be 22 bits, up to a full 4 MBytes could be used, although the DSD 880/30 controller interface could only handle 18 bit addresses up to 256 KBytes. Under RT-11, it is possible to add a bounce buffer for both the DLX.SYS and DYX.SYS device drivers, although I am aware of it being done ONLY for the DYX.SYS device driver. Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.