Abit KR7A-R PCI Speeds

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A look at PCI speeds above 133 MHz. – Joe

SUMMARY: Based on UXD’s Diagnostic Card, the Abit KR7A-R does not enable PCI divisors above /4.

Josh was nice enough to send an email asking me to look into the issue of “hidden” /5 and /6 PCI divisors on the Abit KR7A-R. This board uses the Realtek RTM560-266R clock generator, which supports PCI divisors beyond /4.

To test this out, I used my UXD P.H.D. PCI Diagnostic Card which reads PCI bus speeds directly. This card mounts in a PCI slot; after the mobo completes BIOS, the UXD card takes over. Note there is no OS involvement – in running the tests below – the only disc was a floppy.

For these tests, I ran the most conservative memory settings and underclocked a T-Bird 1400 at high FSBs – I ran it at a 6 multiplier. The intent was to read PCI speeds at various FSBs and PCI settings to see what’s going on:

Abit KR7A-R FSB/PCI Speeds

FSB

PCI Speed

PCI Setting

100

33.71

3/2/1

110

36.93

3/2/1

120

40.27

3/2/1

130

43.60

3/2/1

130

32.69

4/2/1

132

44.38

3/2/1

133

44.51

3/2/1

133

33.53

4/2/1

134

45.02

3/2/1

140

FAIL¹

3/2/1

140

35.20

4/2/1

150

37.80

4/2/1

160

40.24

4/2/1

165

41.53

4/2/1

166

41.78

4/2/1

167

42.02

4/2/1

170

42.76

4/2/1

175

44.02

4/2/1

180

45.29

4/2/1

185

FAIL¹

4/2/1

¹UXD failed to boot.

Once you shift to the 4/2/1 setting at 133 MHz, PCI speeds keep on climbing after that. I could not get beyond 180 MHz (which is impressive), but the pattern is clear – if there was a /5 divisor, it would hit at 166 MHz.

As always, a sample of one, but for this particular board, there are no /5 or better divisors. We’ll continue to experiment, but unless the UXD Diagnostic Card is misreading PCIs (it did not for Iwill’s XP333), it does not look like enhanced divisors are enabled.

If I’m missing something in BIOS to enable these divisors, please drop me a line.

Email Joe

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