Interdata Architecture 32-bit System Differences

Historical Overview

16-Bit Prehistory

There were several 16-bit model number series:

• Single digit model numbers, for example Model 4, Model 5.
• Two digit model numbers, for example Model 70, Model 74.
• Model numbers ending in /16, for example 6/16, 7/16.
• The 1600 series, for example the 1620.

The 16-bit opcode mnemonics appear to anticipate the 32-bit systems. For example, the instruction that loaded a 16-bit register from a 16-bit memory location was LH - Load Halfword. This was not the result of assigning new mnemonics after the introduction of the 32-bit systems. Sales literature for the model 4, the first 16-bit system, uses the halfword mnemonics. A likely explanation is that the opcode mnemonics were chosen to resemble IBM 360 mnemonics for 16-bit operations. Oral tradition claims that the early systems were marketed as less expensive alternatives to IBM 360 mainframes for teaching programming.

It is possible, with considerable care, to create a binary that runs on both 16 and 32-bit Interdata systems. The "common mode" diagnostics are examples.

It is easier, but still requires care, to write assembler source that can be assembled to run on either 16 or 32-bit systems.

The standard OS/32 assembler, CAL/32 (Common Assembly Language/32), will cross assemble for a 16-bit target.

7/32

Legend has it that the 7/32 was a 7/16 HSALU (a 16-bit machine) with different microcode. The 7/32 definitely did have a 16 data bit memory system, requiring double reads or writes to complete 32-bit memory accesses. Early 7/32 systems did have a 16-bit emulation mode, but little or no software made use of it, with the exception of some diagnostics.

The 7/32 used 32KB or 64KB core memory boards.

8/32

It had:

• A 32-bit wide memory system (no more double writes or double reads for fullword accesses)
• Optional single and double precision floating-point hardware
• An optional writable control store.
• An option of 8 register sets instead of 2

The 8/32 used the same core memory boards as the 7/32. A full megabyte was 16 boards.

3220

The 3220 was originally announced as being upgradeable in the future to 4MB. A simple upgrade never appeared. The 4MB upgrade to the 3220 was going to be the 3224 (briefly), then the 3225 (long enough for some manuals to get printed), and finally became the 3230. Owners of early 3220s were offered a discounted upgrade to a 3230 instead.

Kardios, a third party hardware company, did offer a real 4mb 3220 upgrade.

The 3220 introduced:

• A handful of new floating-point instructions
• The Commercial Instruction set (string and decimal arithmetic) instructions
• Improved trap and exception handling
• A serial console to replace the hex display and keypad.

The 3220 used 256KB MOS memory boards using 4116 DIP memory chips that required a 12-volt supply.

3240

The 3240 introduced new memory relocation hardware (MAT) that was capable of addressing 16MB of memory. Configuring more than 2MB required a separate memory cabinet, because the 3240 used the same 256KB memory boards as the 3220. Until higher density memory boards became available the typical 3240 had 2MB of memory configured.

Later, a full 16MB could be configured without a memory expansion cabinet using 3250 memory modified to use the 12V memory power available in a 3240.

The 3240 was notable for the high DMA bandwidth possible.

The model numbers 3242 for a 3240 with two-way interleaved memory or 3244 for a four-way interleaved system are encountered. Most people just said 3240.

3230/3210/3212

The 3230 had a MAT like the 3240. It was different enough to get a whole new model number.

The 3230 originally used 1MB or 2MB MOS memory boards populated with 4164 DIP memory chips that required a 5-Volt supply. Later, 4MB and 8MB memory boards that used 41256 chips became available.

The 3210 was a lower cost version of the 3230.

The 3210:

• Came in a short cabinet, about desk high.
• The standard configuration came with a disk dive mounted in the cabinet, making it almost self contained.
• Had only two memory board slots. This limited memory configurations to 4MB until the higher density memory was available.
• Two backplanes were available. One sacrificed two I/O interface slots to make room for the hardware floating-point option. The other sacrificed the two slots for the hardware floating-point option to make room for two more I/O interface slots.
• Cache memory was eliminated to keep the cost down, or maybe to justify a bigger cost difference between the 3210 and the 3230.

The 3210A was the OEM version of a 3210. It came without a cabinet for customers who supplied their own enclosure.

The 3212 was the 3210 enhanced by restoring the cache from the 3230.

3250

Like with the 3240, the model numbers 3252 and 3254 were used to differentiate systems with different memory interleaving.

The 3250XP was a 3250 shipped with a 3260 backplane.

3200MPS, 3260

The CPU and memory cabinet was much like a standard 3250 CPU and memory cabinet with a different backplane that allowed the connection of APUs and IOPs.

Up to 9 APUs or IOPs could be configured, three to a cabinet, in additional cabinets. The IOPs were 3230 board sets with different cache, different microcode, no memory, and a "RTSM" link back to the CPU. all processors shared the memory in the CPU cabinet.

This was an asymmetrical system, unlike most current multiprocessor systems, which are symmetrical. The OS ran almost entirely on the CPU. APUs ran user code, IOPs ran device drivers. You could hand map programs to processors, or let the OS do it.

Originally, the only attached processor available was the APU. The IOP was introduced later, and later still was an APU/IOP that could be initialized in either role at boot time.

The 3200MPS introduced considerable model number confusion.

• The multiprocessor system was originally introduced as the 3200MPS, joining the 3210, 3230 and 3250 in the product line.
• Then somebody figured out that you might as well start shipping 3250 systems with MPS backplanes. This reduced manufacturing variations, and made it easier to sell APUs as system upgrades.
• Then somebody figured out that if you might as well get some marketing advantage from this backplane change. A 3250 in an MPS backplane (or a 3200MPS without APUs) then became a 3250XP.
• Then it made sense to make them all 3260 systems, with or without APUs or IOPs.
• You might also see 3262 or 3264 for systems with two or four banks.
• You might also see a dash followed by a digit to indicate the number of attached processors.

3230MPS, 3230XP

3205, 3203

The 3205 required a memory expansion board because the memory bus terminator was on the memory expansion board. A 0MB memory expansion board was available to provide termination for systems that had all memory on the CPU board The memory data bus is only 16-bits wide, like the 7/32. Total memory was originally limited to 4MB, but with third party upgrades could reach 16MB.

The 3205 did not have dedicated floating-point hardware, but did have the floating-point instructions microcoded.

The 3203 was a further reduced cost system that eliminated the need (and even the slot) for a memory expansion card by putting the memory bus terminator on the backplane. The 3203 came in a tower case that looked much like an oversized tower PC.

3280

• The 3280 was considerably faster than the 3260 in part due to a four stage instruction execution pipeline.
• The 3280 was designed from the ground up as a multiprocessor system. The backplane accommodated multiple processors, and a more efficient inter-processor control mechanism was designed in.
• Several categories of new instructions were added.
• New memory relocation hardware, the VAT (Virtual Address Translator). This allowed more than 16MB of main memory.

3280E

Micro3200, Micro3, Micro5

3200-2000

PSW Bits

Reserved Memory Locations

Registers and Memory

Data Alignment Checking

Instruction Set