RAM Quality/Speed effect on GPU ?

[zapp22]

Gang
I noticed something in the last day or two that baffles me.
Many of you know that Windows' "display driver stopped responding" crashes can occur with many versions of Radeon and GeForce cards. There are fixes for these issues, with varying success, either via Profiles/Presets with modified core and idle clock values, or by disabling the check routine in Registry.

I've noticed that some combos of deskops/cards are more problematic, and some are no issues at all, and I've never understood the magic. Few laptops exhibit the issue - which also I don't understand fully.

So, on a HP desktop with a modest Radeon 5450 card, I had never seen the problem occur even once despite a LOT of use. But I needed to "borrow" 2GB memory from the machine for a project, then replaced with parts I bought off Ebay, HP P/N's original spec for the desktop. After installing those, all looked good except I got the "display driver stopped" crash/recover for the first time ever.

the card is the same. the card's DDR didn't change..... only the system mem changed and I suspect that the timing of one of those memory sticks is different from the other 3 [more check needed].
Which brings the question: Does faster/better memory somehow help the GPU response?

 

[Berton]

Basically, faster RAM may help. I have a PCIe X16 Radeon video card with 1GB RAM on it [no onboard adapter] but looking in dxdiag see 4095MB video memory available which suggests the card does use part of the System RAM. I have 8GB RAM on the motherboard. I've never received the error you described since building the computer when Win7 was released.

 

[MagusMagnus]

Basically, the lower the CAS the better system-wide performance will be positively affected. That includes the GPU (and to which some system RAM will always be ‘reserved’ for) through the CPU. The CPU (and really, therefore everything else) can only do its job by as fast as the RAM's CAS (foremostly) and clock speed (secondary), will permit it. If there is a bottleneck (say the RAM has a high CAS but a low or moderate clock speed), that will detract from the CPU’s otherwise maximum performance potential, and by extension affect everything else just the same.

CAS Latency = how many cycles of the clock speed it takes for the RAM to respond to anything.
Clock Speed = how many cycles per second the RAM operates at.

Example:
DDR3 2000MHz CAS 9 will take 9/2000 seconds = 45 seconds to respond.
DDR3 1600MHz CAS 6 will take 6/1600 seconds = 38 seconds to respond.

So, the most important consideration when choosing RAM is really the CAS (lowest you can afford) and then the clock speed. Although, I don't see much point in choosing RAM only for its stock clock speed because you can OC it for the same performance increase and for not a cent extra (although, potentially, reducing the operational lifespan of the modules but that's always been the gambit of OC). What you therefore should buy RAM for is the CAS and because the CAS is something you cannot change.

However, if you're going for the absolute maximum clock speed that your motherboard and CPU can support, only then does CAS not matter as much as it otherwise does (that is to say, a very high clock can offset some of the drag of slightly higher CAS modules; something that DDR4 is now utilizing as a standard to beat DDR3, by the way). If you really want extreme "snappiness", you'd go for the lowest CAS available and the highest clock speed your board and CPU support (but that will, on average, cost a very pretty penny; especially if you’re going to do it without OC).

 

[Mellon Head]

Basically, the lower the CAS the better system-wide performance will be positively affected. That includes the GPU (and to which some system RAM will always be ‘reserved’ for) through the CPU. The CPU (and really, therefore everything else) can only do its job by as fast as the RAM's CAS (foremostly) and clock speed (secondary), will permit it. If there is a bottleneck (say the RAM has a high CAS but a low or moderate clock speed), that will detract from the CPU’s otherwise maximum performance potential, and by extension affect everything else just the same.

CAS Latency = how many cycles of the clock speed it takes for the RAM to respond to anything.
Clock Speed = how many cycles per second the RAM operates at.

Example:
DDR3 2000MHz CAS 9 will take 9/2000 seconds = 4.5 milliseconds to respond.
DDR3 1600MHz CAS 6 will take 6/1600 seconds = 3.8 milliseconds to respond.

So, the most important consideration when choosing RAM is really the CAS (lowest you can afford) and then the clock speed. Although, I don't see much point in choosing RAM only for its stock clock speed because you can OC it for the same performance increase and for not a cent extra (although, potentially, reducing the operational lifespan of the modules but that's always been the gambit of OC). What you therefore should buy RAM for is the CAS and because the CAS is something you cannot change.

However, if you're going for the absolute maximum clock speed that your motherboard and CPU can support, only then does CAS not matter as much as it otherwise does (that is to say, a very high clock can offset some of the drag of slightly higher CAS modules; something that DDR4 is now utilizing as a standard to beat DDR3, by the way). If you really want extreme "snappiness", you'd go for the lowest CAS available and the highest clock speed your board and CPU support (but that will, on average, cost a very pretty penny; especially if you’re going to do it without OC).

Small correction on your CAS calculations.