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Old 16 August 2012, 19:44   #1
SpeedGeek
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Join Date: Dec 2010
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Lightbulb Ramsey 04 Write Speedup mod

Hello again my fellow AmiBayer's! Here is another Speedup hack designed to squeeze a bit more performance from A3000/4000 motherboard fast memory! This mod simply causes our friendly DRAM controller chip "Ramsey" to run write cycles 1 clock faster than read cycles thus giving you a performance boost with 70 ns or faster memory installed! I've tested this in my A3000 with a 25 MHz 030 and 50 MHz A3640.

Standard MIPS benchmarks will not show much performance improvement because they mostly read or execute internal CPU instructions within a loop. However, extracting LHA archives to fast memory and other write intensive applications will be noticeably faster!

I've uploaded a simple schematic and an AIBB memory benchmark for the 25 MHz 68030. Also my (CPU Nodatacache) Bustest results are as follows:

25 MHz 68030
BusSpeedTest 0.19 (mlelstv) Buffer: 262144 Bytes, Alignment: 32768
========================================================================
memtype addr op cycle calib bandwidth
fast $07220000 readw 322.8 ns normal 6.2 * 10^6 byte/s
fast $07220000 readl 323.3 ns normal 12.4 * 10^6 byte/s
fast $07220000 readm 266.3 ns normal 15.0 * 10^6 byte/s
fast $07220000 writew 205.3 ns normal 9.7 * 10^6 byte/s
fast $07220000 writel 205.6 ns normal 19.5 * 10^6 byte/s
fast $07220000 writem 181.8 ns normal 22.0 * 10^6 byte/s

50MHz 68040 (Ramsey @ 25 MHz)
BusSpeedTest 0.19 (mlelstv) Buffer: 262144 Bytes, Alignment: 32768
========================================================================
memtype addr op cycle calib bandwidth
fast $07118000 readw 205.2 ns normal 9.7 * 10^6 byte/s
fast $07118000 readl 205.1 ns normal 19.5 * 10^6 byte/s
fast $07118000 readm 211.1 ns normal 19.0 * 10^6 byte/s
fast $07118000 writew 163.7 ns normal 12.2 * 10^6 byte/s
fast $07118000 writel 164.2 ns normal 24.4 * 10^6 byte/s
fast $07118000 writem 163.7 ns normal 24.4 * 10^6 byte/s

Enjoy!

Note: This mod does not seem to work with Ramsey 07! Also, you should run a thorough (CPU Nodatacache) memory test after performing this mod.

P.S. I'm using the 10 ns GAL from my A3000 16MB SIMM mod to provide the necessary OR gate function as seen here:

http://eab.abime.net/showthread.php?t=104336
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Last edited by SpeedGeek; 15 October 2020 at 19:40.
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