sh5, memory ampliation,...

[bender]

well, i've been speaking with some friends and they have toold me that the sh5 it's 100% pin compatible with the sh4 and supports 100% the sh4
also about memory, there have been some interesting memory upgrades for the gp32 replacing the ram chips. I think it should be possible to replace those chips for the dreamcast for similar ones that have more capacity(the chips could perhaps be found in some pcs dimms

What do you think guys? has anyone tried to do those mods? i think ithe dreamcast scene needs something similar, will solve the optimization problems with the ports and we still would have the compatibility with the commercial games
any site i have missed?
thnks

[quzar]

[quote author=bender link=board=hardware;num=1095614726;start=0#0 date=09/19/04 at 12:25:26]well, i've been speaking with some friends and they have toold me *that the sh5 it's 100% pin compatible with the sh4 and supports 100% the sh4[/quote]

thats just not true. It is not pin compatible at all, only instruction set compatible.

I know because over a year ago i asked a representative of SuperH the same question:

I can answer your question, which is quite complex and involves both
CPU
architecture and specific device information.

1. The SH-4 is a 32-bit CPU with an instruction set branded as
SHcompact. The SH-5 is a 64-bit CPU that supports the SHcompact
instruction set and adds a new multimedia instruction set called
SHmedia.

This means that binaries written for SH-4 would run on SH-5. However in
the Dreamcast there are many peripherals and system components and
changing CPU is not really a practical option unless you have access to
the all the source code written by Sega. You could contact Sega but I
doubt they will give out this material.

2. Pin compatibility
The Sega Dreamcast was built with the SH-4 CPU and a set of peripherals
e.g. memory interface, UART etc. The actual device was manufactured by
Hitachi Semiconductor (now called Renesas Technology, see
www.renesas.com) but it is not for sale any more.

There is no version of the SH-5 that is pin compatible with the SH-4
device used in the Dreamcast so it is not possible to swap out the
chips.

Sorry that we do not have any better solution for you.
Best regards
Mark Jones
Business Development

[bender]

very good answer.
thnks 8)

interesting site with the gp32 ram upgrade, pics inside
http://www.cobbleware.com/gp32/gp32ram.html
i've been thinking in emailing this guy asking about his opinion about the dreamcast and a ram mod, but my english really sucks and i don't really know what i should ask. if anyone thinks this is interesting, please do it

[Alexvrb]

[quote author=quzar link=board=hardware;num=1095614726;start=0#1 date=09/19/04 at 17:36:51]
thats just not true. It is not pin compatible at all, only instruction set compatible.[/quote]
That's not what he said quzar. He said it wasn't pin compatible with the SH4 in the Dreamcast. In other words, it probably IS pin compatible with typical SH4s. Also, it runs all the standard SH4 instructions, but does a standard SH5 have the extra instructions in the DC's variant?

[quzar]

[quote author=Alexvrb link=board=hardware;num=1095614726;start=0#3 date=09/19/04 at 19:40:45]
That's not what he said quzar. He said it wasn't pin compatible with the SH4 in the Dreamcast. In other words, it probably IS pin compatible with typical SH4s. Also, it runs all the standard SH4 instructions, but does a standard SH5 have the extra instructions in the DC's variant?[/quote]

Since he was talking about the dreamcast, when he said Sh-4 i assumed he meant the SH7750(?) that was in the Dreamcast, not another SH-4 chip. About the backwards compatibility, I'm not sure =P.

[bender]

about the ram mod i think it should be possible. The sh4 should be able to address more than those 16mb.

[Kamjin]

The memory is more than likely possible, but the work involved.. ehhh..
In reality there hasn't been a real need for more memory, if it's a question of large carts for emulators, then it would be easier to build an interface for them off the expansion bus.
I think the way to go is to still examine the overclocking, speed is for the emu's is still a higher priority..

[Alexvrb]

[quote author=quzar link=board=hardware;num=1095614726;start=0#4 date=09/19/04 at 22:09:04]Since he was talking about the dreamcast, when he said Sh-4 i assumed he meant the SH7750(?) that was in the Dreamcast, not another SH-4 chip. About the backwards compatibility, I'm not sure =P.[/quote]What I want to know is more info on the SH4A chips they're working on. Not as powerful as the SH5s, but they may well have more in common with the older chips. Damnit, someone should build a DC-compatible box and throw one of those in there, it wouldn't be an expensive addition. Use it as part of the sound subsystem in the Xbox 2 or something. Like the Genesis did :P, it has a SMS compatibility mode.

[bender]

[quote author=Kamjin link=board=hardware;num=1095614726;start=0#6 date=09/20/04 at 20:54:38]The memory is more than likely possible, but the work involved.. ehhh..
In reality there hasn't been a real need for more memory, if it's a question of large carts for emulators, then it would be easier to build an interface for them off the expansion bus.
I think the way to go is to still examine the overclocking, speed is for the emu's is still a higher priority.. [/quote]

i was thinking in putting a lot of Mb and trying to run naomi games using a dc, lol ;D
if your overclocking thing gets into an stable point, without corrupting the vmu files, more ram could perhaps help for some arcade emus, neogeo (cartridge system) or an n64 one(i'm just dreaming ). I think, there are also some linux games that can't be ported due to the lack of some Mb

[bender]

Speaking about the sh5 with a guy, he says that there could be between 2 and 4 different versions of this micro. He tells me that one of those was 100% pin compatible and supported 100% the sh4 instruction set, last time he looked at. Perhaps this compatible sh5 it's not being sold anymore and the reason because quzar got that answer
I don't have a link to post so i can't verify this, though :