QX-11 vs QX-16

[vprada]

Now that I have my QX-16 operational and booting MSDOS I have been able to figure out some of the differences and similarities between the QX11 and the QX16.

Similar things:
Hardware interruptions: Both the QX-11 and the QX-16 do not follow the IBM standard for Interruptions. On the EPSON machines the first hardware interruption is mapped to software interruption INT 70. In both QX-11 and QX-16 INT 70 is the power down detection and INT 71 is the hardware timer (really important interupt). Here is a table of the interrupt table I found on both machines.

	qx-11	qx-16
Base	INT 70h	INT 70h
Timer	INT 71h	INT 71h
Keyboard	INT 75h	INT 74h
FDC	INT 74h	INT 76h

Hardware components : Both the QX-11 and QX16 share the same hardware design to access the floppy disk drive. Both use a upd765 controller , a GAFDDC gate array and propietary EPSON disk drives. Also in both data separation is done via a SED9401COB ship. (The Equity I also uses the same hardware combination for the floppy drives).

The video display is a little different. The QX-16 have a video card based on the 7220 graphics processor. By default the 7220 video card is used by default when running on Z/80 mode, but In my tests I've seen the 8088 BIOS accessing the 7220 graphic card (I still need to tell for sure what DIP switch combination is needed for the BIOS to use the 7220 on 8088 mode). The QX-11 have a Gate arrya named GAVDP that provides native video quite alike the video output produced by the 7220. This native video mode of the QX-11 can produce a RGB color output of 8 colors.

The QX-16 is able to emulate an IBM CGA card using the APX-ICRT video card. The APX-ICRT card comes standard with the QX-16 (at least that's how it was sold in the US). On the QX-11 there is a VNS-ICRT option video card the also let's you emulate an IBM CGA card on the QX-11. As a matter of fact, this two cards (APX-ICRT and VNS-ICRT) share the same design.

QX-11 VNS-ICRT	QX-16 APX-ICRT

For the RTC (Real time Clock) both the QX-11 and QX-16 use the same HD146818 but listening to different IO ports.

At the software level, the both are running MS-DOS v 2.11 although they are different releases. As a matter of fact the EPSONBIO.ASM file in the MSDOS source code implemented certain patches that explicity say will break VENUS (VENUS is the code name for the QX-11 hence the VNS-ICRT and the VENUS BOARD name printed on the QX-11 motherboard and accesories). The code name for the QX-16 was APOLLO (hence the APX- suffix used in all the QX-16 hardware and accesories)

the QX-11 and the QX-16 also share the same version of GW-BASIC version 2.02. The QX11 runs release 1 and the QX16 run release 2D. One thing I notice on the QX-16 is that depending on the position of the DIP switches, some graphic routines will be disabled. Other than that I was able to run the same basic programs on both yhe qx11 and the qx16 without any modifications.

 

[vprada]

I found out another coincidence between both machines. The RTC IRQ in both is IRQ10, with a software interupt at INT 7Ah

	QX-11	QX-16
Base	INT 70h	INT 70h
Timer	INT 71h	INT 71h
Keyboard	INT 75h	INT 74h
FDC	INT 74h	INT 76h
RTC	INT 7Ah	INT 7Ah

 

[vprada]

Here I wanted to share a comparison between the size of the QX-11 and the QX-16. Both machines have the same capabilities at the hardware level. 1 serial port, 1 centronics port, 2 floppy drives. Both machines have an 8088-2, 2 floppy units and up to 512Kb of RAM.

On the QX-11 Epson replaced many of the discrete ICs, like the Interupt controller, serial controller, timer, igs video card and others with gate arrays significantly reducing the size of the machine and at the same time giving thr machine more capabilities, like support for 8 colors when connecting a RGB monitor, support for external floppy drives (like the TF-20 or PF-10 serial floppies) the QX-11 also have a 300bps internal modem, cartridge support, joystick inputs, 3 voice sound support, etc.

here is a couple pictures of both the QX-11 and the QX-16 next to each other.