AEA PCB-88

[WD4MTW]

I've held on to this ISA packet board for years, even replaced the battery a few years ago. I have a nagging question that Timewave appears not to be able to answer at the time I enquired about it around 2005 when I upgraded my two pk-232s. The board was perfectly operational on a '286 machine for a couple of years. Upgrading to a '486 during the 90's, the board apparently wouldn't communicate with any software. Same with a Pentium 90 and subsequent 300 and 500 mhz boards that still had ISA slots.

I've always wondered if the bus speeds of the later computers were the reason the board couldn't be initalized and it required the slower speeds of the old machines. DOS Utilities such as Whoa or Moslo didn't make a difference or the old AT command of ctrl+-

I'm just wondering if this was a bus speed issue or if there was a failure between the transition between the 286 and 486 upgrades. Besides Pkterm that AEA suppled for DOS, I couldn't access the board using the old Aries or Gary's later WinXP DOS or Windows versions.


Anyone know if these boards are dependent on old XT/AT ISA bus speeds? 

[W9GB]

TAPR's APRSSIG group discussion in February 2006,
suggests that the issue with the AEA PCB-88 ISA expansion card is indeed a bus clock speed issue.
http://www.tapr.org/pipermail/aprssig/2006-February/012649.html

N8VEM Project Group currently has an 8088 ISA computer build,
http://www.malinov.com/Home/sergeys-projects/sergey-s-xt
 if you are looking for a potential computer to drive.
http://n8vem-sbc.pbworks.com/w/page/4200908/FrontPage

[WD4MTW]

Thanks for the links. The TAPR posting confirms my original suspicions. I've never known anyone to have owned one of these boards. While I ran into a lot of DOS software that increasingly would not run or run properly, the supplied Packterm and XPware software would work with the pk-232, so I never doubted it was the host software. The board would be identified as an unknown modem and physically held the port and irq the board was set to, but using generic terminal software such as Procomm wouldn't register any response either. I've sort of suspected the 8250 UART as it was a problem with earlier serial cards and modems on faster AT compatibles. Later cards used the 16450 and 16550 UARTS. I wonder if anyone ever investigated that. The link for the backplane project was interesting and is actually why I'm holding on to the board. I've been given a backplane with a 386i processor card and embedded DOS along with a serial/parallel combo card that was used in a marine communications terminal that might be a future project.

[W9GB]

I've sort of suspected the 8250 UART as it was a problem with earlier serial cards and modems on faster AT compatibles. Later cards used the 16450 and 16550 UARTS. I wonder if anyone ever investigated that. The link for the backplane project was interesting and is actually why I'm holding on to the board.

You are taking me back to early 1980s with this observation.

YES, the late 1970s hobby computers (Apple II), the original IBM Serial Card (used in IBM PC and XT), and the AST 6-Pak from that era used the 8250 UART.

The later IBM Serial / Parallel card (1984) used the 16450 UART.
The 16450 and 16550 UARTS have a small buffer.
I think you will find that it is the UART as well as specific 7400 chips (slow)

[WD4MTW]

I took a look at the board and it despite the schematic showing a 8250, the board has a
socketed 16450 UART. I'm going to try the 16550.

[W9GB]

CHECK to see if the board uses any "timing" from the ISA bus
as well as bus interface chips (speed).

[WD4MTW]

The ISA bus connections do not include the B20/4.77 clock or use B30/14 mhz.  The UART has an independently derived clock source from an onboard rock and last I checked I recall it's presence at the clock pin. The bus glue chips between the UART and the ISA bus are a 74hct245 bus transceiver, 2  74HCT138's as 3/8 line decoders, a 7400 and 74125 both HCT as well. Presently, the only slow ISA bus machine that I have alive is a 75 mhz Packard Hell that I use for RSS and GPIB control in my shop. I have an old ISA HP/GPIB card running happily, so there's no problem with the bus. The PCB-88 is otherwise undocumented beyond two schematics. Unlike the PK-88 and PK-232 that had hardware manuals available. The PK-88 is near identical I understand except of course for the bus interface section in question and has a serial interface instead. Randy at Timewave seemed to have no knowledge of the board, no supplemental docs available, and did no repairs. He could only could sell me a new battery several years ago.

[W9GB]

When Randy, at Timewave, bought the AEA product line of TNCs and Multi-mode controllers in 1996, he only got the AEA documentation, tooling and boards for current or recent products.
http://www.geocities.jp/tnc_gallery/pcb88-e.htm

The PCB-88 is an ISA COM (Serial board: bus interface, 16450 UART) with the PK-87/PK-88 era TNC on the same ISA card.
So proper setup means setting the IRQ and hardware port (COM1-COM4) ... that is important with newer motherboards that have built-in COM ports and IRQ dedicated for specific hardware devices (mouse, keyboard, parallel port, etc.).

Lyle Johnson, TAPR did add the 9600 baud card to the PCB-88 in 1992.
He mentions 26-pin header and TAPR TNC-2 similarities.
http://www.ka9q.net/psr-48.pdf

AEA made this ISA card, as well as an earlier PK-90 and PK-89 external TNC that has marginal to non existent documentation.  What does exists on Internet comes from former AEA customer support or employees.
http://www.tapr.org/pipermail/aprssig/2005-December/011332.html
==
For example:  Bob Donnell, KD7NM worked in AEA's Customer Support Group from 1990 until March 1994 and provided the AEA PK-90 information that you will find on Internet or support forums today.
http://www.tapr.org/pipermail/aprssig/2005-December/011304.html
The AEA PK-90 is a commercial TNC version of the amateur radio AEA PK-87 TNC.

Rick, W4PC at CSS had this basic information (to operate software):
Switches 1-4 provide the base address (hardware) for the COM port when turned on

SW-1    $03f8   COM1:
SW-2    $02f8   COM2:
SW-3    $03e8   COM3:
SW-4    $02e8   COM4:

Switches 5-8 provide the IRQ when turned on

SW-5     5
SW-6     4
SW-7     3
SW-8     2

PkTerm '99 does work with the PCB-88 and
allowed you to run the TNC under Windows 95/98/Me and Windows NT/2000.