2.3.  Memory chips on 5900XT graphics cards

2.3.1.  Memory chips on some cards overclock to 900-1000MHz, while on others – only to 750MHz or something. Why?

Such graphics cards are equipped with memory of several different types. The most popular chips are Hynix AF-28 (2.8ns cycle time) and Samsung GC-2A (2.86ns – according to Samsung’s specifications). It’s all right with the Samsung memory – it works exactly to its specs, overclocking to about 800MHz on some especially lucky specimens. The Hynix memory is a curious thing. To my personal opinion, Hynix has a higher yield of 2.5ns and even 2.2ns chips than of 2.8ns ones. So they just re-mark some chips as 2.8ns. As a result, the worst chips overclock to the predictable 800MHz, while the best ones notch 1GHz and higher!

Statistics suggests that there are more graphics cards with Hynix’s memory chips than with Samsung’s.

2.3.2.  What memory is better – from Hynix or Samsung?

If you can choose between two cards with Hynix and Samsung memory chips, you should prefer Hynix. You won’t be worse off for such decision and you’ll have a chance of enjoying great overclocking if you’re lucky.

2.3.3.  Are there any cards with 2.5/2.2ns memory?

Yes. There are 5900XT-based graphics cards with Hynix AF-25 (2.5ns) and overclocking is usually appropriate, to 850-900MHz. This memory is installed onto most of MSI 5900XT cards; sometimes you may come across a lucky sample from other brands (particularly, AOpen, Gainward and Prolink). Graphics cards from Galaxy were spotted in the market with Hynix AF-22 memory (i.e. 2.2ns), but I have no info about their overclockability. Also 2.2 ns chips can be found on all InsideTNC FX 5900XT Tuning cards.

2.4.  What about GPU overclocking?

It’s simpler with the GPU, although with some reservations. The 5900XT is manufactured from all NV35 chips – 5900 as well as 5900 Ultra ones. Thus, the overclocking potential varies in a wide range. I personally saw frequencies from 430MHz to 520MHz (with the regular cooling, without modding), 460-470MHz being the average mark. Alas, you can only know the overclockability of the core after installing the card into your computer.

2.5.  What’s better: good overclocking of the GPU or memory?

Of course, everything depends on the ratio of the two frequencies and on what exactly you mean by “good overclocking”. However, 5900XT cards respond better to GPU overclocking. That’s why the owners of graphics cards with the Samsung memory shouldn’t grief too much: a good core may well compensate for “weak” memory.

2.6.  How do I seek for an overclockable 5900XT?

You may just browse through cards, testing as many of them as you can, preferably of different brands and from different manufacturing batches. This ideal method never fails. It is not easily realizable, though, so here’s a piece of more practical advice:

• try to find a card with the Hynix memory;
• thermal monitoring is bad, rather than good for overclocking (see Item 3.4.3);
• if you’re not going to use the card with its own cooling system, pick up a board with individual heatsinks on the memory chips; it would be just easier for you to change the cooling system;
• an important thing you should keep in mind sounds like that: if your friend has a highly overclockable Gainward/Gigabyte/Sparkle/etc, it doesn’t mean you’ll be that lucky, too (see Items 2.3.1, 2.4 and 2.7).