Re:AMD ships microcode update to disable some branch prediction
by BuildTheRobots on Friday January 05, 2018 @05:17PM
(#16082244)
Without wanting to side track the the conversation too much, I'm guessing I'm right in my assumption that implementing x86 cores on an FPGA (so we can add wire traces to the cpu after the fact) is still way to slow and expensive to even be close to a reality?
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Re:AMD ships microcode update to disable some branch prediction
by mitchty on Friday January 05, 2018 @05:59PM
(#16082539)
Correct, FPGA simulation of a 3.0Ghz processor means you'd be waiting on the order of weeks to boot into linux.
I work for a company that works with Intel on new things. Lets just say the FPGA's they use are... really expensive, and despite being capable of simulating a design fast, are still very slow.
By expensive I found out $20 million per FPGA simulator was on the low end. And I think that would simulate at the rate of about 10mhz for the amount of transistors/internal setup present.
Fpgas are cool, but a poor choice for fixing this issue.
You could probably do it for up to an 80386 with some $400ish dollar FPGA's.
Re:AMD ships microcode update to disable some branch prediction
by BuildTheRobots on Saturday January 06, 2018 @06:57PM
(#16088203)
Weeks! - Thank you, I knewit was slower, but that's such an order of magnitude slower I don't even know how to calculate it :)
Re:AMD ships microcode update to disable some branch prediction
by mitchty on Tuesday January 09, 2018 @11:07AM
(#16107129)
Processor bring up is fun to learn about, then you learn you don't want to know how that sausage is made any longer. >.<
Re:AMD ships microcode update to disable some branch prediction
by monocasa on Friday January 05, 2018 @05:57PM
(#16082521)
Yeah, for something like a modern x86 core, you'd need something like this.
https://www.cadence.com/content/cadence-www/global/en_US/hom...
It'll cost you ~$1M and run at a few MHz.