View Full Version : Original CPU?

August 16th, 2012, 12:29 PM
I have an IBM Model 5160 that Iíve had for the past 17 years. My Dad got it for me free when he saw it. He thought Iíd like the vintage computer. :) Funny how it seemed vintage even then. :)

Anyway, every once and awhile I pull it out of the basement and turn it on to make sure it still works. Today I was messing around with it and I remembered that I swapped CPUís on it for a faster one. I remember that it didnít seem to do anything and I canít remember if I left ďupgraded CPUĒ in there or put the original back in. Before I go over to my Dadís house and start digging through my stuff trying to find the original CPU, I looked at the CPU in there and itís an:

Intel P8088-2
Copyright 1978.

When I ran Landmark speed test on it, I comes up as an Intel 8088 4.771 MHz CPU performing like a 2.47Mhz AT.

When I looked up the P8088 CPU, it says on the Internet that itís an 8MHz CPU. So does this seem like the original CPU for the Model 5160? I really havenít a clue, my first PC was a Tandy 1000 TL/2 and I haven't much a clue about that one either. :)

August 16th, 2012, 12:35 PM
That CPU likely came from a turbo "clone". To the best of my knowledge, most of the original 5150/5160 CPUs were made by AMD.

August 16th, 2012, 12:37 PM
Someone with much more knowledge about the 5160 will pop in [ah, yes, someone did], but in the meantime.. even if the CPU is an 8MHz part, it won't run at anything more than 4.77 MHz because presumably the 5160 never had a 'turbo' button to increase the clock frequency (IIRC that was something which the clones introduced).


August 16th, 2012, 12:38 PM
Most likely the original CPU was 8088 (without -2 suffix). XT's were usually equipped either with Intel P8088 (in plastic DIP package), or AMD D8088 (ceramic DIP package), and rarely with IBM 4481480 (which is either IBM-remarked Intel chip, or 8088 made by IBM... not sure, anyone knows who made them?).

It is unlikely that you would have an 8088-2 in the original XT.

Now, the CPU clock frequency (in early machines, till 486DX2 with clock multiplying) is determined by the clock generator (and the crystal oscillator connected to it) and not by the CPU itself. Marking on CPU simply reflects the maximal frequency it will work on (8088 without suffix - 5 MHz, 8088-2 - 8 MHz, 8088-1 - 10 MHz). So if you stick an 8088-2 into an XT, it will run on 4.77 MHz (just as fast as the original 8088 would run).

August 16th, 2012, 12:51 PM
One other thing--the 8088-2 that you have was manufactured in the second half of 1986, when the 5160 was in its last throes (The 5160 was officially discontinued in April, 1987). You can check the dates of the other chips in the system (usually in the form of yymm or yyddd or something similar)--I'll wager that they all fall before that of the CPU. By looking around the 5160, you probably will find a manufacturing date for the system as well.

August 16th, 2012, 12:55 PM
On the cable to the speaker at the front there is usually a tag with the date.

August 16th, 2012, 01:31 PM
My XT has a speaker tag with December, 1984 on it and an AMD D8088 CPU dated 1982.

August 16th, 2012, 01:44 PM
I went over to my Dad’s and I found the original CPU, but there are two in the box and I think one is a math coprocessor?

The first one is:
1982 AMD

The other one is:
1982 AMD


I'm beginning to think those are both 8088 CPU's. What's the middle number? A serial number?

August 16th, 2012, 02:06 PM
The middle number is the date and origin code. The first is the 34th week of 1983; the second is the 17th week of 1983. I'm not sure about AMD fab codes from then, but perhaps someone still knows.

1982 is just the copyright date of the design.

August 16th, 2012, 02:12 PM
That’s interesting, I wonder how I managed to get two CPU’s manufactured within 17 weeks of each other.

I imagine it doesn’t make much of a difference of which CPU goes in there? I’ll put the 8117EM CPU in computer then.

August 16th, 2012, 02:41 PM
I'm beginning to think those are both 8088 CPU's. What's the middle number? A serial number?

Both are CPUs. Math coprocessor is Intel 8087.

August 16th, 2012, 02:57 PM
My XT has a speaker tag with December, 1984 on it and an AMD D8088 CPU dated 1982.

If you're referring to (C) 1982 AMD, it is not the production date, but a copyright (copyleft* ?!) date. The production date is specified in the middle line, and for AMD it is usually in format of 'YYWWXXXX' where YY is year, WW - week, XXXX - some letters (batch code?!).

* It was some anarchy till 1984 regarding copyright information on 808x CPUs: AMD put (C) AMD; Siemens - (C) Siemens; Japanese manufacturers (NEC, Fujitsu, Mitsubishi) didn't put any copyright at all. Somewhere in 1984 it was a lawsuit between NEC and Intel regarding microcode rights for V20/V30 CPUs. One of the NEC claims was that Intel forfeited copyright rights since copyright notices were not printed on many 8088 processors. This made Intel enforce second source manufacturers to put proper copyright notices.

August 17th, 2012, 09:18 AM
Thanks for the help everyone, got the original CPU back in the machine.

April 23rd, 2018, 07:37 PM