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Intel SDK-80

This is one of the first computers I played with. It's on my list of things to be resurrected.

I scanned the MCS-80 System Design Kit Users Guide. It's big (17 megs).

Here's an article from Electronics Australia, July 1977.

The SDK-80 is a Multibus form factor PCB but the actual bus is not implemented -- only the power pins are connected.

The board came with 256 bytes RAM and 1 kilobyte EPROM, expandable to 1 kilobyte RAM and 4 kilobytes of EPROM. There are also two 8255 programmable peripheral interfaces (one with the kit, one user supplied) giving 48 bits of parallel I/O, and an 8251 USART with RS-232 and current loop interfaces, and provision for baud rates from 75 to 4800. There's also a prototype area provided.

SDK-80 as sold

(Picture off the 'net) This is how the SDK-80 was sold -- you can see what you're getting and how it all fits together.

Tiny Basic

My SDK-80 came with two 2708 EPROMs. I dumped parts of it waybackwhen, using my MEK6800D2 kit, and found that it's a copy of Li-Chen Wang's Palo Alto Tiny BASIC as published in Dr Dobbs, May 1976. There are some changes though.

My dump:
31 90 5f 3e ff c3 69 06 e3 ef be c3 68 00 3e 0d
f5 3a 14 3c 87 c3 a3 06 cd 85 03 e5 c3 41 03 57
7c ba c0 7d bb c9 41 4e 1a fe 20 c0 13 c3 28 00

0000 31 90 5F  LODI SP, 5F90
0003 3E FF     LODI A, FF
0005 C3 69 06  JMP 0669    ST1
0008 E3        XCHG HL,(SP)
0009 EF        RST 7     0028 / SS1 / IGNBLK
000A BE        CMP M
000B C3 68 00  JMP TC1
000E 3E 0D     LODI A, 0D
0010 F5        PUSH AF
0011 3A 14 3C  LD   A, 3C14  OCSW
0014 87        IOR  A
0015 C3 A3 06  JMP  06A3  OC2
0018 CD 85 03  CALL 0385  EXPR2
001B E5        PUSH HL
001C C3 41 03  JMP  0341  EXPR1
001F 57        CHAR 'W'
0020 7C        LOD A,H
0021 BA        CMP D
0022 C0        RET NZ
0023 7D        LOD A,L
0024 BB        CMP E
0025 C9        RET U
0026 41 4E     CHAR 'AN'
0028 1A        LD A,(DE)
0029 FE 20     CMP ' '
002B C0        RET NZ
002C 13        INC DE
002D C3 28 00  JMP 0028   SS1

October 2015: I completed the dump of the first EPROM. You know what's amazing? I've had these EPROMs since the eighties and they were not new then and the code is still intact. And they don't even have stickers on the windows.

MEK6800D2 dumping 2708

I think I can conclude that this Tiny Basic was not intended for the SDK-80. The SDK-80 has RAM from 0x1000 to 0x13FF while this port sets up the stack at 0x5F90 and has OCSW at 0x3C14. This sort of feels like a system with (space for) 8K ROM (0x0000 to 0x1FFF) and 16K RAM (0x2000 to 0x5FFF) -- but I could be wrong of course...


Somewhere along the way I acquired this SBC-732 Combination Analog Input Output Board.

[Image] Hit Count hits since 2015-07-16.

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