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Original CPU?

M

MrRedHat

Experienced Member
Joined
Aug 16, 2012
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75
Location
Wisconsin
I have an IBM Model 5160 that I’ve had for the past 17 years. My Dad got it for me free when he saw it. He thought I’d 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 CPU’s on it for a faster one. I remember that it didn’t seem to do anything and I can’t remember if I left “upgraded CPU” in there or put the original back in. Before I go over to my Dad’s house and start digging through my stuff trying to find the original CPU, I looked at the CPU in there and it’s an:

Intel P8088-2
8615FPP
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 it’s an 8MHz CPU. So does this seem like the original CPU for the Model 5160? I really haven’t a clue, my first PC was a Tandy 1000 TL/2 and I haven't much a clue about that one either. :)
 
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).

-Tor
 
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).
 
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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.
 
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:
D8088
8334LMA
1982 AMD

The other one is:
D8088
8317EM
1982 AMD

EDIT:

I'm beginning to think those are both 8088 CPU's. What's the middle number? A serial number?
 
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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.
 
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.
 
Stone said:
My XT has a speaker tag with December, 1984 on it and an AMD D8088 CPU dated 1982.
Click to expand...

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.
 
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Chuck(G) said:
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.
Click to expand...

at least in my experience The 5150 REV A. boards (16-64k) had all intel chips, even the supporting logic chips. later boards 64-256k have AMD chips. and all the 5160's ive messed with 256k & 640k boards both had AMD processors & supporting logic chips.

maybe someone installed the 8088-2 CPU thinking they would get a performance boost, not realizing the board would still just run the CPU @ 4.77mhz but thats just a guess as to why it might be in there.
 
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