On Sat, 26 Jun 2021 10:23:51 +0100
James Harris <james.h...@gmail.com
> On 25/06/2021 17:27, wolfgang kern wrote:
> > On 25.06.2021 12:59, James Harris wrote:
> >> I don't know about you but I never cease to be amazed by the
> >> hardware we have available. I was looking for some figures on
> >> memory bandwidth and came across this:
> >> https://www.forrestthewoods.com/blog/memory-bandwidth-napkin-math/
> >> There's a bunch of stuff there that's worth a read but perhaps the
> >> headline is that the author says RAM can be accessed at tens of
> >> gigabytes per second!
> >> Such figures are backed up by
> >> https://en.wikipedia.org/wiki/List_of_interface_bit_rates
> >> so they seem to be correct.
> >> Mind blowing, isn't it!
> > yes, but still a bit too expensive for a normal desktop PC.
> > I'm happy with my 64GB DDR3 RAM and the 8GB DDR5 VRAM. it
> > would need very short lines to achieve the mentioned speed.
> Curiously, I remember someone here (his initials were WK, IIRC)
> telling me that it was not feasible to test memory before handing it
> out as that would take too long. That is, in fact, why I went looking
> for figures on memory performance.
Unfortunately, I think his initials were RP ...
I recall telling someone - likely you - that I wasn't about to test my
memory chips for errors because of the time it takes. I.e., defective
memory chips are usually fairly noticeable with some type of glitch or
error or page fault or crash or corrupted data or corrupted screen,
etc. E.g., I always know when it's time to blow the dust off of one of
my memory chips here because of random app crashes.
> Have to say that whether it's with DDR5 or DDR3 ISTM quite feasible
> to do the test on memory before handing it out. That's especially so
> as the kernel would only need a small amount of memory to start with.
> All the rest could be tested in the background, later. And even that
> would be finished maybe 5 or 6 seconds. Testing of memory looks
> feasible. :-)
Well, the memory testing via the BIOS tester on a 2007 Dell PC takes
"forever". I don't recall if the machine has 1GB or 4GB etc. The BIOS
code which tests memory goes through numerous test repetitions on the
same memory locations and ranges, and has about a dozen different
memory tests. I think the code is all 16-bit. That PC was randomly
rebooting or locking up. It needed lots of fuzz and dust removed.
IIRC, memtest86+ loads from DOS. So, it's likely 16-bit code too, or
possibly 32-bit if was compiled for DPMI. 32-bit might not be too bad.