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[fasquardon]

So I've read that the main bottleneck on Dwarf Fortress performance is the insane RAM needs of the program, and that a massive (256mb+) cache on the CPU should make Dwarf Fortress run much better.  I was curious if anyone had run Dwarf Fortress on one of the [non-mobile] CPUs with Iris Pro onboard graphics and the 128mb LV4 cache those chips have and if Dwarf Fortress runs better on those CPUs?

fasquardon

[Max™]

Well, I ran it on my Ivy Bridge i3 and integrated graphics, it worked fine though it eventually started to wear out the graphics portion so I finally got a replacement for my old dead GPU.

The L4 cache helps naturally, the more cache between CPU and RAM the better really.

[fasquardon]

Well, I ran it on my Ivy Bridge i3 and integrated graphics, it worked fine though it eventually started to wear out the graphics portion so I finally got a replacement for my old dead GPU.

The L4 cache helps naturally, the more cache between CPU and RAM the better really.

It wore out part of the chip?  I didn't think that was even possible unless feeding the chips non-stock voltages somehow...

fasquardon

[jecowa]

I think Iris Pro is only available on laptop processors, isn't it? I think you'd be better off with a high-end desktop i5.

I don't think the cache on the CPU will solve the RAM problem. Dwarf Fortress' problem with RAM is that it can only use up to 2GB while larger worlds can need a bit more than that. Once Dwarf Fortress is a 64-bit app, it will be able to use more than 2GB RAM.

[fasquardon]

I think Iris Pro is only available on laptop processors, isn't it? I think you'd be better off with a high-end desktop i5.

I don't think the cache on the CPU will solve the RAM problem. Dwarf Fortress' problem with RAM is that it can only use up to 2GB while larger worlds can need a bit more than that. Once Dwarf Fortress is a 64-bit app, it will be able to use more than 2GB RAM.

No, Iris Pro is available on a selection of desktop i5s and i7s and xeons.  So there are plenty of high-end chips with the 128mb lv4 cache on them.

And, while Science! on system bottlenecks while running Dwarf Fortress is rather lacking, from searching these forums and on reddit, I've found a couple analyses that point at to the main bottleneck being to do with how fast a system fetches and carries data between the CPU and RAM.  (For example, Dwarf Fortress appears to give exactly no figs about memory bandwidth, but cares greatly about memory latency, which is very unusual.)  Apparently, this may at least partly due to the amount of cache misses Dwarf Fortress generates - the large cache on chips with Iris Pro graphics on them should greatly help with that.  But I've not seen any Science! done on this question since chips with Iris Pro came out in 2013.  Hence my question.

And while worldgen uses alot of RAM, normal fortresses don't seem to use much at all.  I've never heard of anyone using more than a gb on fortress mode.

fasquardon

[Max™]

Well, I ran it on my Ivy Bridge i3 and integrated graphics, it worked fine though it eventually started to wear out the graphics portion so I finally got a replacement for my old dead GPU.

The L4 cache helps naturally, the more cache between CPU and RAM the better really.

It wore out part of the chip?  I didn't think that was even possible unless feeding the chips non-stock voltages somehow...

fasquardon

Well, I was only playing df and using two monitors, and the integrated GPU isn't the main chip.

It just started giving graphical glitches and whatnot after a while, stopped once I switched to a new card.

[fasquardon]

Well, I ran it on my Ivy Bridge i3 and integrated graphics, it worked fine though it eventually started to wear out the graphics portion so I finally got a replacement for my old dead GPU.

The L4 cache helps naturally, the more cache between CPU and RAM the better really.

It wore out part of the chip?  I didn't think that was even possible unless feeding the chips non-stock voltages somehow...

fasquardon

Well, I was only playing df and using two monitors, and the integrated GPU isn't the main chip.

It just started giving graphical glitches and whatnot after a while, stopped once I switched to a new card.

Huh.  Interesting...

I think Iris Pro is only available on laptop processors, isn't it? I think you'd be better off with a high-end desktop i5.

So as far as I can find, the versions of Iris Pro on mobile processors does not have the 128mb lv4 cache.  Which also means I gave this thread a misleading title, since when I started it, I thought all chips with Iris Pro also had the lv4 cache.

Derp.

I've now edited the thread title to be more accurate.

fasquardon

[Putnam]

Dwarf Fortress' problem with RAM is that it can only use up to 2GB while larger worlds can need a bit more than that. Once Dwarf Fortress is a 64-bit app, it will be able to use more than 2GB RAM.

No, not at all. DF's problem is that RAM is unbelievably slow relative to CPU cache speeds and DF shunts a lot of memory around. I can't read assembly very well, but I know what moving memory around in it looks like, and some profiling tells me that cache misses are a ridiculous amount of CPU time for DF.