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tlccomp
Joined: 11 May 2006
Posts: 1212
Location: Southeast Wisconsin, USA
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 Posted: Thu Jun 22, 2006 6:02 am Post subject: Strange 287 Mathco |
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Seen one of these?
Any more info?
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fRaSsL
Joined: 31 Mar 2003
Posts: 1570
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| Posted: Thu Jun 22, 2006 6:31 am Post subject: |
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Yes, I have 3 of them. This a little adapter board that alters the clock frequency of the copro. In many cases the clock is higher than the mobo would have given  So it's a little speed up. There are also modules lowering the clock speed! c't magazine has shown that speeding up the copro is not effective in all cases. So a 12MHz 286 is not fast enough to 'feed' a 20 or 25MHz FPU 
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JAC
Joined: 24 Jul 2005
Posts: 3469
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| Posted: Thu Jun 22, 2006 6:44 am Post subject: |
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| fRaSsL wrote: | | Yes, I have 3 of them. This a little adapter board that alters the clock frequency of the copro. In many cases the clock is higher than the mobo would have given So it's a little speed up. There are also modules lowering the clock speed! c't magazine has shown that speeding up the copro is not effective in all cases. So a 12MHz 286 is not fast enough to 'feed' a 20 or 25MHz FPU |
ah very interesting. The i287 is the my favourite copro. I like the XL's.
Speaking of which, is the XL the copro you can use anywhere? It adapts to the system frequency. ( kind of like the 387 16-33Mhz). |
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tlccomp
Joined: 11 May 2006
Posts: 1212
Location: Southeast Wisconsin, USA
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| Posted: Thu Jun 22, 2006 7:07 am Post subject: |
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| fRaSsL wrote: | | Yes, I have 3 of them. This a little adapter board that alters the clock frequency of the copro. In many cases the clock is higher than the mobo would have given So it's a little speed up. There are also modules lowering the clock speed! c't magazine has shown that speeding up the copro is not effective in all cases. So a 12MHz 286 is not fast enough to 'feed' a 20 or 25MHz FPU |
Thanks.
It did come off of a board running at 25MHz.
Do we know whose mathco it is? |
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fRaSsL
Joined: 31 Mar 2003
Posts: 1570
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| Posted: Thu Jun 22, 2006 7:14 am Post subject: |
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Most likely it's a IIT 2C87.
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JAC
Joined: 24 Jul 2005
Posts: 3469
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| Posted: Thu Jun 22, 2006 7:36 am Post subject: |
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| Looks like an intel i287XL to me. The little brown strip on the edge of the chip is the clue. Take the heatsink off. |
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gshv
Joined: 01 Feb 2003
Posts: 7898
Location: Fairfax, VA USA
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| Posted: Thu Jun 22, 2006 7:42 am Post subject: |
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I think it's an IIT co-processor. Intel 80287XL FPU has maximum speed of 12.5 MHz.
Gennadiy |
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JAC
Joined: 24 Jul 2005
Posts: 3469
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| Posted: Thu Jun 22, 2006 7:53 am Post subject: |
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ah yes, IIT 2C87 rated up to 20Mhz... but I am sure have seen info on the i287XL overclocked. 12.5Mhz is only its rated speed.
Why the heatsink anyway? ITT used advanced CMOS with low power. ? |
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tlccomp
Joined: 11 May 2006
Posts: 1212
Location: Southeast Wisconsin, USA
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| Posted: Thu Jun 22, 2006 7:55 am Post subject: |
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| gshv wrote: | I think it's an IIT co-processor. Intel 80287XL FPU has maximum speed of 12.5 MHz.
Gennadiy |
Jac is right... took off the heatsink and it is an Intel C80287XL. |
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JAC
Joined: 24 Jul 2005
Posts: 3469
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| Posted: Thu Jun 22, 2006 7:59 am Post subject: |
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| Thankyou I was hoping you were going to take it off. |
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gshv
Joined: 01 Feb 2003
Posts: 7898
Location: Fairfax, VA USA
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| Posted: Thu Jun 22, 2006 8:14 am Post subject: |
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| tlccomp wrote: | | gshv wrote: | I think it's an IIT co-processor. Intel 80287XL FPU has maximum speed of 12.5 MHz.
Gennadiy |
Jac is right... took off the heatsink and it is an Intel C80287XL. |
Interesting... 12.5 MHz came from original Intel datasheet. Either I don't have the latest version of the datasheet, or the FPU was overclocked.
Gennadiy |
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fRaSsL
Joined: 31 Mar 2003
Posts: 1570
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| Posted: Thu Jun 22, 2006 8:28 am Post subject: |
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The ones I have came all with a IIT.
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el_gecko
Joined: 25 May 2005
Posts: 1553
Location: Nice, France
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| Posted: Thu Jun 22, 2006 8:42 am Post subject: |
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Take off the heatsink and it'll be a no-name FPU lol 
Don't think that the ink could resist...
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My microprocessor collection: The Gecko's CPU Library |
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JAC
Joined: 24 Jul 2005
Posts: 3469
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| Posted: Thu Jun 22, 2006 8:50 am Post subject: |
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| gecko54000 wrote: | Take off the heatsink and it'll be a no-name FPU lol
Don't think that the ink could resist... |
The printing is on the side, not on the gold cap. |
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