Date: 2002-04-18 09:01:56
Hi Spiro, >> LPT vs ISA speed limitations I've looked at this a fair bit having baselined dozens of PCs and LPT card combinations, ISA, VLB, PCI, on-board, etc The fastest access I've achieved is 1MHz. ISA cards are a little slower than PCI, but it seems that access to the LPT port is intentionally limited. Perhaps a legacy issue for ensuring printers work? On one machine which allowed the ISA speed to be selected as a ratio of bus speed I tried various settings. The difference between the 8MHz and the "bus/2" option (which should have been 16.666MHz) only increased access speed by 30% for 8bit ops, but nearly got the 100% increase for 32bit ops. This machine had a 32-bit VLB IO card. My most recent thinking is that IDE (newer ATA protocols) must have overcome these speed limitations, especially for PCI cards. I've yet to build a test PC (I don't feel like accidently erasing my HDD), but my theory is to use a secondary device or channel for access. Ruud pointed out to me that IDE a bus, not a device so it will need latches added to the end of it before it can be implemented for LPT sytle devices. It is possible however that the IDE bus is still limited to ~1MHz since all HDD (even old ones) work with newer cards. The improvement in speed may be due DMA by the newer devices. enough ramblings from me.... - Nick PLEASE TAKE NOTE: The contents of this email (including any attachments) may be privileged and confidential. Any unauthorised use of the contents is expressly prohibited. If you have received this email in error, please advise us immediately (you can contact us by telephone on +61 8 9441 2311 by reverse charge) and then permanently delete this email together with any attachments. We appreciate your co-operation. Whilst Orbital endeavours to take reasonable care to ensure that this email and any attachments are free from viruses or other defects, Orbital does not represent or warrant that such is explicitly the case (C) 2000: Orbital Engine Company (Australia) PTY LTD and its affiliates Message was sent through the cbm-hackers mailing list
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