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--- blog:transputer_tmb08_repair [2020/12/09 08:10] – [IO Speed Tuning] john
+++ blog:transputer_tmb08_repair [2020/12/09 08:29] (current) – [IO Speed Tuning] john
@@ Line 122: / Line 122: @@
 ===== IO Speed Tuning =====
-The default link speed from the root transputer to the PC host is moderately low; in the order of 270-280KBytes/sec. When I rewrote the Linux transputer driver for kernel 3.x.y I was getting approximately 100KBytes/sec more. Some of this could be down to the architecture of the host system (I was previously using a 200MHz Pentium Pro, rather than the current 133MHz 5x86/486), but it was pointed out to me that this could potentially be improved by tuning various BIOS options.
+The default link speed from the root transputer to the PC host is moderately low; in the order of **270-280KBytes/sec**. When I rewrote the Linux transputer driver for kernel 3.x.y I was getting approximately 100KBytes/sec more. Some of this could be down to the architecture of the host system (I was previously using a 200MHz Pentium Pro, rather than the current 133MHz 5x86/486), but it was pointed out to me that this could potentially be improved by tuning various BIOS options.
+  * Standard BIOS settings are:
+    * **1/4** Bus clock as ISA speed (33MHz/4 = 8.//something//)
+    * **8** clock cycles as 8bit ISA IO recovery time
+I tried a sequence of changing ISA clock and then 8bit IO recovery time, testing in between each change via //ispy// to verify host IO link speed. These are the results:
 {{:blog:tmb08_io_tuning.png?700|}}
+The first increase in IO speed comes from both increasing the ISA clock from the standard 8MHz (bus / 4) to 11MHz (bus / 3), which gains an additional **22-24KBytes/sec**, as well as decreasing the IO recovery time from the standard 8 cycles to 5 cycles, giving us another **32-33KBytes/sec**. Further decreases to the IO recovery time below 5 cycles __do not__ show any improvement.
+CPU level 1 and motherboard level 2 caches are already optimal (write-back supported on both) and memory timings are already set correctly for the type and speed of the modules installed, so there are no further gains to be made there.
+Still, the overall improvement from the base setting is approximately **55-56KBytes/sec**. __Taking us from 270-280KBytes/sec to 333KBytes/sec__.
 ===== Transputer Network Configuration =====