CPU Shack

I used to have it in my head that the Voyager probes were about as powerful as an Apple II computer. But it's hard to make a direct comparison as the probes have three computers made of two processors each, running at 1/20th or 1/6th the speed of an Apple. So it's not a one-on-one comparison in any way, but for discussion purposes:

An original Apple II used a MOS 6502 8-bit word CPU clocked at 1.023 MHz and typically had 4Kb to 48Kb of RAM. It ran about 500,000 instructions per second [1].

Computer Command System (CCS) - two 18-bit word interrupt-type processors with 4096 words each of plated wire memory. It ran about 25,000 instructions per second. [2]

Flight Data System (FDS) - two 16-bit word machine with modular memories and 8198 words each of memory. It ran about 25,000 instructions per second. [2]

Attitude and Articulation Control System (AACS) - two 18-bit word machines with 4096 words each of memory. The AACS ran about 80,000 instructions per second. [2]

So maybe the total amount of computing power is equal? The total memory on a Voyager was about 32K [3], and since the word sizes were bigger, theoretically they could access larger chunks of memory in a single instruction? What's for sure is that a single CCS is at least an of magnitude less powerful than an Apple II.

More info:

1) http://www.classiccmp.org/cini/pdf/Apple/Apple%20II%20Reference%20Manual%20-%20Woz.pdf

2) http://www.cpushack.com/space-craft-cpu.html

3)…

> I wonder where all those machines ended up. Would love to get one and play with them.

A lot of them (probably the vast majority) simply got dumped, alas. I personally decided to dump a Challenge (basically an Onyx without the Reality Engine graphics: https://en.wikipedia.org/wiki/SGI_Onyx). As in: I could have it if I wanted it, I used it for years but it had to go when it was obsoleted. I could have put the rack in my basement, but I'm not young anymore and it wouldn't be that many years before it would be a headache to get it out. So I said: "Sorry. Dump it."

Smaller is more manageable of course - I have a number of O2, O2+, Indy computers and an Octane. And a Fuel.

At work we had a bunch of Origin servers as well. All dumped.

Back to the Onyx - when it came out in 1993 I had some access to one, I worked in the same computer room for weeks at the time on an off. Played with the various graphics demos, mostly. But I watched what the guys were doing with it. It was very impressive, a huge step up from anything else, and the sheer performance and memory bandwidth of the thing was one big reason I argued for getting an SGI Challenge for a later technical project. And I was right on that, as it turned out. Nothing else could do the job at the time (in this price segment, at least).

As for the CPU speed - Like the R4000, the R4400 internal pipeline ran at a higher rate (internal multiplier): https://www.cpushack.com/MIPSCPU.html

Looking at the specs for the TI TMS9900, Zilog Z80, and the MOS 6502, the TI chip came in a 64-pin DIP and required +5V, -5V, and +12V power supply while the other two chips came in a 40 pin DIP package and only required a +5V power supply.

The 6502 was cheap (<$30), the Z80 was more expensive at introduction, but looking at price lists, dropped down close to the same price as the 6502 within a few years.

from https://www.cpushack.com/2015/02/05/ti-tms9900sbp9900-accidental-success/:

" In 1978 a 9980 cost $30 while a TMS9900 cost $70."

Also, in the comments from the above link:

"Many years later, the processor architect for the TMS9995 (Karl Guttag) pointed out to me that whatever context switch benefits the WP offered were quickly outweighed by the required memory access cycles only a handful of instructions into an interrupt service routine. It was a false economy."

Details: The IBM AT/370 used standard bios on the motherboard, and the two 68k custom cards had their own bioses. The 68ks were very heavily modified by one of the motorola engineers.

Its the second version of the AT Bios that was disgusting was verion 2, that ran on 6mhz 286s and prevented you from swapping the crystal for a 16Mhz/8Mhz speed up. The first version had bugs, and the third version was for the 8Mhz machines. ( still a few bugs ).

This is the AT/370:

https://en.wikipedia.org/wiki/PC-based_IBM_mainframe-compatible_systems

https://www.cpushack.com/2013/03/22/cpu-of-the-day-ibm-micro-370/

https://anycpu.org/forum/viewtopic.php?f=22&t=350

There was one additional model of the IBM AT: THE IBM XT/286: An AT class mother board in an XT sized case.

https://www.dosdays.co.uk/computers/IBM%20PC-XT-286%20(5162)/ibm5162.php

picoJava processors (Sun Microsystems) https://www.cnet.com/culture/sun-releases-complete-chip-design-for-free/

Patriot Scientific's Ignite processor family https://www.cpushack.com/2013/03/02/chuck-moore-part-2-from-space-to-greenarrays/

ARM Jazelle technology https://developer.arm.com/documentation/ddi0222/b/introduction/about-the-arm9ej-s-with-jazelle-technology

https://www.eetimes.com/nazomi-offers-plug-in-java-accelerator-for-wireless-handsets/

It's all dot-com era stuff and Sun Microsystems also created a Java OS that could run directly on hardware without a host operating system.

That's about it

Best independent source I can find is http://www.cpushack.com/CPU/cpu4.html#Sec4Part14.

I noticed whilst writing a verilog implementation - seeing the @PC+ relative modes for immediate data made me dig out my PDP-11 reference card.

The number of addressing modes has been halved, gaining a bit for register encoding, and the status register is now in the register file (R2), and R3 is used to generate various constants depending on mode.

Compare and contrast:

* https://en.wikipedia.org/wiki/PDP-11_architecture#CPU_registers
* https://en.wikipedia.org/wiki/TI_MSP430#MSP430_CPU