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Wanted: 10mHz 80287XL

raifield

Experienced Member
Joined
Aug 3, 2010
Messages
174
Location
NJ, USA
Anyone have a 10mHz 80287XL they would be willing to sell? I bought a 10mHz 80287 on eBay, but the seller claimed that he never received my initial purchase order and hadn't shipped after three weeks. He graciously refunded my money, but I'm thinking my luck might be better here.

I'd like a 80287XL over a 80287 for the synchronous CPU/FPU speed and quicker instruction time, though I suspect in practice I'd never notice the slower 80287.
 

Shadow Lord

Veteran Member
Joined
Jun 16, 2010
Messages
3,163
Location
California
Anyone have a 10mHz 80287XL they would be willing to sell? I bought a 10mHz 80287 on eBay, but the seller claimed that he never received my initial purchase order and hadn't shipped after three weeks. He graciously refunded my money, but I'm thinking my luck might be better here.

I'd like a 80287XL over a 80287 for the synchronous CPU/FPU speed and quicker instruction time, though I suspect in practice I'd never notice the slower 80287.

Ther is no such a thing. The 80287XL could run at multiple speeds so it could be coupled w/ different CPUs at different speeds. Heck it was even used early on in the 80386 era as the FPU for the 386. As long as you get a 80287XL you are golden. They are rare, but not that rare - in fact there are two sellers on ebay with new ones w/ the i287 stamp (more covetted in certain circles for the look). Price wise you should expect to pay about that much ($30-$40) although I have seen the non-stamped (functionally exactly the same) go for $20-$30. Or you could pickup stones 80287-10.

A bit of Googlefu:

I quickly scanned through 80287 and 80287XL datasheets, and here performance/instruction set differences I found:

- XL processor is almost twice as fast when executing basic arithmetic instructions (add, sub, mul, div).
- other instructions, such as load, store, special, etc, could be slower or faster depending on the instruction, operand type, etc, but on average they have comparable execution time to 80287.
- The 80287XL divides external frequency by 2, while the 80287 divides it by 3. Because of this, when the XL processor is plugged into 80287 socket, it will run at 50% higher frequency than the 80287.
- The XL has a few additional 80387 instructions - sin, cos, etc.
 

raifield

Experienced Member
Joined
Aug 3, 2010
Messages
174
Location
NJ, USA
Thanks. The last time I looked for the XL on eBay I had only seen the $95 one.

I had known about XL running at multiple speeds, not sure why I typed it out the way I did. I guess a more clear version would have been "Seeking 80287XL for my 10mHz 286".

I bought the $40 one, so here's hoping.
 
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