From: Baltissen, GJPAA (Ruud) (ruud.baltissen_at_abp.nl)
Date: 2005-05-19 11:39:50
Hallo allemaal, Gábor wrote: > we can replace eg 6510 in C64 with 65816. There were some > article to replace the CPU in the C64, The 65816 has the ABORT input, which IMHO is meant for page faults etc. Some articles: www.baltissen.org/02to816.htm www.baltissen.org/10to816.htm I'm updating the last page at this moment and therefore the GIFs aren't available yet. Another thing is that this page mentions that "Replacing the 6510 is quite forward and doesn't need an explanation IMHO" but that is not true if you want to use the complete 16 MB range. So her is the extra info you need: 1) an extra 74ALS573 latches the data to generate the address lines A16..23, clocked by an ivertor 2) a 688 8-bit-comparator checks which 64 KB segment is addressed. 3) extra 541's buffer the addresslines towards the C64 4) a 245 buffers the databus 5) a 125 buffers R/W 6) a number of pull-up resistors The idea is that when the 65816 addresses an address outside the first 64 KB, the address lines AND the R/W line towards the C64 are disabled. The effect for the system is that it seems that the CPU wants to read address $FFFF, completely save IMHO, whether it is the ROM or the RAM under it. One could even go a step further by disabling RDY during that period as there is no need to halt the 65816 as it is addressing an area outside he original C64. Tri-stating the 65816 is not needed at all here as the buffers can perform this function. I've build an hack where I put the buffers described above between the 65816 and the C64 just to proof that the idea could work. No 688 and no I/O but the C64 worked fine as long as a program didn't try to change the I/O port. -- ___ / __|__ / / |_/ Groetjes, Ruud \ \__|_\ \___| URL: Ruud.C64.org =====DISCLAIMER================================================================= De informatie in dit e-mailbericht is vertrouwelijk en uitsluitend bestemd voor de geadresseerde. Wanneer u dit bericht per abuis ontvangt, verzoeken wij u contact op te nemen met de afzender per kerende e-mail. Verder verzoeken wij u in dat geval dit e-mailbericht te vernietigen en de inhoud ervan aan niemand openbaar te maken. Wij aanvaarden geen aansprakelijkheid voor onjuiste, onvolledige dan wel ontijdige overbrenging van de inhoud van een verzonden e-mailbericht, noch voor daarbij overgebrachte virussen. The information contained in this e-mail is confidential and may be privileged. It may be read, copied and used only by the intended recipient. If you have received it in error, please contact the sender immediately by return e-mail; please delete in this case the e-mail and do not disclose its contents to any person. We don't accept liability for any errors, omissions, delays of receipt or viruses in the contents of this message which arise as a result of e-mail transmission. Message was sent through the cbm-hackers mailing list
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