3 ms·

8-issue means you can issue 8 things all together, all at once, all in a single cycle. The front end feeds the back end. 3-issue FE means you can give the BE

8-issue means you can issue 8 things all together, all at once, all in a single cycle. The front end feeds the back end. 3-issue FE means you can give the BE 3 things per cycle. 5-issue BE means you can crunch 5 things from the FE per cycle. FE = branch prediction, decode, instruction cache BE = schedule, execute, load/store, data cache

stephencanon 12y ago
I'm 99.9% sure that DannyBee understands this, because he's a smart guy, and that he's saying "that's how it works in marketing".
- sliverstorm 12y ago
  I don't know DannyBee to know his smarts- but I do see the potential sarcastic undertone :) I'll leave my comment though for the edification of others.
ChuckMcM 12y ago
The question for me is whether you can retire the FE issue with a BE dispatch, and if so pull in another FE issue. So can you get the EU to the point where the all 5 of the BE units are subscribed and the three instructions in the front end have been pre-cracked waiting for a BE slot to free up? So ... Ins 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ... FE: [ ] [ ] [Ins0] BE: [ ] [ ] [ ] [ ] [ ] FE: [ ] [ ] [Ins1] BE: [ ] [ ] [ ] [ ] [Ins0] FE: [ ] [Ins1] [Ins2] BE: [ ] [ ] [ ] [ ] [Ins0] FE: [Ins1] [Ins5] [Ins6] BE: [ ] [Ins3] [Ins4] [Ins2] [Ins0] FE: [Ins1] [Ins5] [Ins7] BE: [Ins6] [Ins3] [Ins4] [Ins2] [Ins0] And then maybe zero retires, that lets Ins1 proceed and it retires 1, 2, 3, 4, which lets 5 proceed, that lets 6 retire and then 7 proceeds. But until I get a closer look at the TRM this is all speculation.
- sliverstorm 12y ago
  The question for me is whether you can retire the FE issue with a BE dispatch, and if so pull in another FE issue. Almost certainly yes. It's supposed to be fully out-of-order, which means it should have a fully functional scheduler in between the FE & BE. Not to mention, given modern memory latencies (vs. clock speed), letting the FE run ahead is important for performance.

stephencanon 12y ago

I'm 99.9% sure that DannyBee understands this, because he's a smart guy, and that he's saying "that's how it works in marketing".

sliverstorm 12y ago
I don't know DannyBee to know his smarts- but I do see the potential sarcastic undertone :) I'll leave my comment though for the edification of others.

ChuckMcM 12y ago

The question for me is whether you can retire the FE issue with a BE dispatch, and if so pull in another FE issue. So can you get the EU to the point where the all 5 of the BE units are subscribed and the three instructions in the front end have been pre-cracked waiting for a BE slot to free up? So ... Ins 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ... FE: [ ] [ ] [Ins0] BE: [ ] [ ] [ ] [ ] [ ] FE: [ ] [ ] [Ins1] BE: [ ] [ ] [ ] [ ] [Ins0] FE: [ ] [Ins1] [Ins2] BE: [ ] [ ] [ ] [ ] [Ins0] FE: [Ins1] [Ins5] [Ins6] BE: [ ] [Ins3] [Ins4] [Ins2] [Ins0] FE: [Ins1] [Ins5] [Ins7] BE: [Ins6] [Ins3] [Ins4] [Ins2] [Ins0] And then maybe zero retires, that lets Ins1 proceed and it retires 1, 2, 3, 4, which lets 5 proceed, that lets 6 retire and then 7 proceeds. But until I get a closer look at the TRM this is all speculation.

sliverstorm 12y ago
The question for me is whether you can retire the FE issue with a BE dispatch, and if so pull in another FE issue. Almost certainly yes. It's supposed to be fully out-of-order, which means it should have a fully functional scheduler in between the FE & BE. Not to mention, given modern memory latencies (vs. clock speed), letting the FE run ahead is important for performance.